A hydraulic pump unit (HPUs) is an arrangement of interconnected components that control hydraulic energy. It is an integral component in most hydraulic systems.

A hydraulic system is any component that uses a fluid to generate and transmit energy from one point to another within the enclosed system. This force can be in the form of linear motion, force or rotary motion.
This is based on the Pascal’s Laws. Don’t worry, you’ll understand how this law works when I’ll be discussing the working principle of these power packs.
Therefore, whenever you refer to hydraulic power units, it is basically a system that generates pressure or force based on the above fundamental aspects. You can use them in applications that require heavy and systematic lifting.

At times, the hydraulic pump units may also be referred to as the hydraulic power packs, hydraulic power pack units or hydraulic power units. They all refer to the same component. To generate, transmit, distribute and control this energy, HPU uses different hydraulic components.

Components of hydraulic power pack

They include:

• Electric or diesel motors
• Hydraulic valves
• Reservoirs
• Hydraulic gear pumps/li>
• Suction Filters
• Air breathers for fill oil into Hydraulic Reservoirs
• Central manifold blocks
• Electrical Control systems, like buttons remote and wireless remote

It is these parts that are interconnected to form an electric driven power unit, i.e., a single component. Other power units may have more components depending on the complexity of the design.

You’ll learn more about these components in Chapter three.

For instance, a small hydraulic power unit may have fewer components compared to those in the heavy lifting industries.
Moreover, it will depend on the hydraulic power unit design. You will learn about the design process in Chapter 2 and the manufacturing process in Chapter 7.
Today, we use power packs in a wide range of applications, both in our daily lives and a number of manufacturing processes. This is mainly due to:

• Cost efficiency
• High density of power transition
• Reliability and safety
• Flexibility in design

For example, I am sure you have seen a small hydraulic jack that lifts heavy trucks. They use a small amount of hydraulic fluid transmit a huge amount of force, enough to lift the truck.

Even the huge buses and trailers use hydraulic systems in their breaking systems. With all these in mind, we can go ahead to classify the existing types of power packs available in the market.

There are many types of hydraulic power packs in the market. As you will realize later in this hydraulic power pack eBook, the classification may depend on the construction, function and size of the power pack.

Let’s begin with:

Type of Power Packs Based on Construction/Design

First, I want to note that the construction design will determine the primary function of the hydraulic system.
Broadly, in this section, I will introduce you to two main categories:

• Single acting hydraulic power pack
• Double acting hydraulic power pack

I will elaborate more on their functions in this Chapter, section 1.3, but, before that, let’s have a quick overview of single and double acting hydraulic cylinders.
Single acting hydraulic cylinders

In single acting hydraulic cylinders, the hydraulic fluid acts on only one end of the piston. Therefore, to push the piston back to its original position (retraction), the cylinder uses a compressed air, mechanical spring, a flying wheel or gravity load.

A double acting hydraulic cylinders

A double acting power pack unit is where the working hydraulic fluids acts alternately on the two ends of the piston. That is, it uses the hydraulic power to extend and retract the piston.

You can learn more about single and double acting hydraulic cylinders from this video, courtesy of the Engineering Technology Simulation Learning Videos.

Type of Power Packs Based on the Primary Applications

This is a common classification criteria where you can describe a specific equipment based on the nature of its application.

Again, you’re going to learn more about this as I discuss the specific applications of hydraulic power packs in this Chapter 1, section 1.4.

I will list all possible uses of all these hydraulic systems.

Types of Power Packs Based on Size

In most cases, describing this hydraulic equipment based on its size or capacity is a common phenomenon. Basically, the classification criteria describe various performance specifications.

The main common performance specifications include:

• Flow rate
• Working pressure
• Tank volume
• Electric motor power
• Fluid type, i.e. mineral oil HL or HLP

For the scope of this hydraulic power unit eBook, I will focus on four main criteria:

1) Micro Power Pack Units

The Micro hydraulic power packs are suitable for applications where space is limited. They are portable due to their small size.

They are compact in size and available as either single or double acting. Due to their flexibility, you can operate them in either single or double acting without necessarily having a solenoid control valve.

All you need to do is reverse the motor movement. Such micro power packs have dual pressure relief valves, giving separate control options.

Also, a dual check valve reduces the effects of noise and induced pressure. Their tank capacity may range between 0.1 to 3 liters.

To drive the hydraulic pumps, the micro hydraulic power pack uses either 150 to 800 watt DC motors.

Remember, all these specifications may vary depending on the manufacturer.

2) Mini Power Pack Units

The mini hydraulic power packs are suitable for mobility applications. They are slightly larger than the micro power pack units.

For these hydraulic power packs, space is never an issue.

Due to their size, they are also referred to as small hydraulic power packs or small hydraulic power units.

They are available in different configurations such as horizontal or vertical mounting with a reservoir tank capacity ranging between 0.8 and 30liters. It uses a DC 0.8kW to 4.0kW motor, or AC 0.75kW to 7.5kW motor. The voltage of DC motors is DC 12V/24V or DC36v/48v, and the voltage of AC motors is AC 110V/220V/230V/380V/415V.

With the advancement in technology, there are portable hydraulic power units that come with remote control options.

3) Standard Hydraulic Power Pack Units

The standard hydraulic power pack units are designed for in-plant operations. They are mainly used for industrial applications.

Such hydraulic power packs create huge power and high flow rates. They can handle heavy loads for a long period of time.

Their tank capacity is about 180 liters, with a flow rate of about 100 liters/minute. In most cases, you’ll find that most standard hydraulic power packs have a motor rating of about 30kW.

4) Hydraulic Power Unit Stations

The Hydraulic power unit stations are designed for specific applications. These may include sewage treatment, construction and mining applications, just to mention a few.

Mostly, they are available in custom designs to meet the specific requirement of any unique application.

Broadly, these are the main types of hydraulic power packs available in the market. As you can see, as the sizes increase, their capacity and power also increases.

Next, I want to introduce you to the various functions of hydraulic power packs. This will make it easy for to understand what you’re going to learn in Chapter 2 of this eBook.

In this section, you’ll learn about how a single acting and double acting hydraulic power packs work. Generally, the main difference between the two is the force that moves the piston from one end of the cylinder to the other.

Here is all you need to know about:

1.3.1 Single Acting Hydraulic Power Pack

In a single acting hydraulic cylinder, the hydraulic fluid enters the cylinder only in one direction. As a result, it pushes the piston to the opposite side of the hydraulic cylinder.

To return the piston to its original position, there must be an external intervention, i.e., a force that will push the piston to its initial position. This force can be in the form of spring tension, gravity or compressed air.

So, assuming your single acting cylinder has a spring on one side, then you should expect;
When the hydraulic fluid enters the cylinder, it will exert pressure on the piston head, pushing it in the opposite direction. As a result, the spring will be compressed between the opposite side of the piston and the cylinder.

During the retraction process, the cylinder weight holding valve (solenoid release valve) is opened, releasing pressure due to the hydraulic fluid. As a result, the spring tension (due to the compression) will force the piston back to its original position, pushing the hydraulic fluid back to the reservoir.

Normally, you will find that this single acting hydraulic actuator system is fitted with only one hydraulic hose pipe i.e., one oil connection pipe.

They are common in applications where either weight, gravity or other external force is available to push the cylinder in the direction opposite to that of the hydraulic fluid.

Therefore, it is only a single acting power unit that can operate these systems. The single acting power packs are a perfect choice for dump trailers, tipper applications, hydraulic lifts, etc.

A single acting hydraulic power pack can, thus, achieve the “power up, gravity down” required to operate any single acting cylinder.

These accessories are popular since they can be mounted in any direction, besides being cheap compared to the double acting cylinders.

1.3.2 Double Acting Hydraulic Power Pack

First, I will explain to you how a double acting hydraulic cylinder works. These are systems where the hydraulic fluids act interchangeably on both ends of the piston.

Unlike the single acting hydraulic cylinders, that achieve “power up, gravity down”, a double acting hydraulic cylinder achieves a “power up, power down”.

As you can see from the image above, these systems are designed with two hydraulic fluid hose pipes, taking fluid into and out of the extreme ends of the hydraulic cylinder.

In some applications such as snow-plows and hydraulic presses, double acting hydraulic systems are a perfect choice due to the following reasons.

Firstly, you don’t have to worry about the existence of enough force to return the piston to its original position. The pressure hydraulic fluid will automatically do this for you.

Secondly, they have a small hydraulic reservoir. Therefore, they are a perfect choice where the space available is limited.

Thirdly, corrosion is reduced since the rod is lubricated by the fluid that flows in both ends of the hydraulic cylinder. This reduces the possibility of wear and tear.

Apart from these, the double acting cylinders are readily available. So, even getting the spare parts is easier compared to the single acting.

Therefore, when you have such a hydraulic system, your only option is to choose a double acting hydraulic power pack. They are the only accessories that can drive a double acting cylinder system.

In hydraulic power units, the term “hydraulic power” refers to the process where a system of interconnected pipes with pressurized fluids can generate, control and transmit mechanical power from one point to another.
This makes it possible to do certain tasks such as lifting items, blasting rocks in the case of excavators, motor vehicle braking systems, etc.

I know you’re wondering how this is even possible.
Don’t worry, I will explain.
First, hydraulic power depends on Physics Laws that was first investigated by Blaise Pascal. Pascal was a French mathematician, physicist and religious philosopher.
In his experiments, Pascal deduced that: “Pressure applied to a confined incompressible fluid at any point is transmitted undiminished throughout the fluid in all directions and acts upon every part of the confining vessel at right angles to its interior surfaces and equally upon equal areas.” Source:Machinery Lubrications.
This became the Pascal’s Law or Pascal’s Principle that govern the design and construction of the hydraulic systems we use today. As a result, Pascal (Pa) became the SI unit for pressure.

Based on this law, we can derive a number of hydraulic equations you can use to analyze and designs hydraulic systems. But first, let’s analyze the relationship between the Pascal’s Law and hydraulics

1) Hydraulics Power Systems vs. Pascal’s Law

Hydraulic systems use incompressible fluids to transmit forces from one point to another. This fluid is always in an enclosed system, thereby obeying Pascal’s Law.
Therefore, any change in pressure, at one point of this fluid will be transmitted to the entire system of the fluid.
Of interest to engineers in the hydraulic power pack manufacturing industry is the number of times the force that causes the change in pressure can be multiplied (opposite side of the hydraulic cylinder).
You’ll find that, the small piston will require a low amount of force to lift a large amount of load in the larger piston.

This brings us to an essential concept of mechanical advantage (MA) of the entire system. We get MA by dividing the distance over which the force is applied by the distance over which the load moved.
In short, you’ll find that the Pascal’s Law allows forces to be multiplied.
In reality, this how we expect these physical variable to change.

As you can see, there are a number of equations above. Therefore, for design purposes, let’s review hydraulics equations, based on the Pascal’s Laws.

2) Hydraulic Equations

In fluid mechanics, a fundamental equation that describes how hydraulic power units work is:
“P=F2/A2=F1/A1 ”,
Basically, this illustrates how hydraulic fluid transmits power within an enclosed system. In this basic hydraulic formula the letters represent three physical variables: “P” for pressure; ”F” for force and “A” for area.
When you want to analyze the working principle of hydraulic power in details, you need to consider other aspects such as the viscosity of the fluid, conservation of energy, etc. Follow this link for a practical illustration of hydraulic power calculations.
Next, you’ll learn the actual process of creating a hydraulic power.

A hydraulic power unit has a wide range of components that help to generate the required amount of energy or force to perform a specific task.
The number of components in any hydraulic drive system will depend on the complexity of its design and the specific application.
Generally, to create a hydraulic power, you systems should have these four basic components:

• Power section; this is the main source of hydraulic system.
• Control section; it controls both the ratio and direction of the oil.
• Reservoir; stores hydraulic oil
• Actuator; coverts hydraulic power into useful mechanical work

You can see how these systems are interconnected in the figure below:

With these in mind, let’s go ahead to describe how you can generate a hydraulic power.

1) Generating Hydraulic Power

First, the process begins from the power section. Here, the pump driven by a prime mover.
The prime mover can be a diesel motor, an electric motor or an internal combustion engine. At this stage, the prime mover will help to convert mechanical energy into fluid energy.
The prime mover and the hydraulic pump are coupled together via a shaft. As the shaft rotates, it drives the output shaft of the gear pump.
This will result in a pressure difference between the inlet and outlet of the pump. That is, the inlet pressure will be higher than the outlet pressure.
As a result, the hydraulic fluid will begin to flow from the reservoir to the control section. This hydraulic fluid passes through a strainer before flowing into the hydraulic pump.

Remember, a hydraulic power is as a result of both oil flow and pressure. The two are create in the hydraulic pump.
The pump forces hydraulic fluid through the valves that close and open depending on the level pressure in the system.
Hydraulic circuits have a wide range valves that help control the flow fluid such as the main relief valve, one-way valve and 3 position, 4 port hand operated valve.
The main relief valve protects the hydraulic pump in case of any back pressure. In case of a back pressure, the hydraulic fluid will flow back to the reservoir (tank).
At times, you’ll find some hydraulic systems having very many valves. This will depend on the complexity of the hydraulic system.
Of course, this is mainly the control section of the hydraulic system. Let’s have a quick overview of this section.

2) Components of a Hydraulic Control Section

Depending on the design of the system, it may have:

• Cartridge valves
• Superimposed valves
• Central manifold block
• Stacked manifold block
• Solenoid valve
• Throttle valve

Again, when the hydraulic circuit is in a neutral position (when the hydraulic fluid not flowing to the cylinder), the fluid will flows back to the reservoir through the neutral circuit.
When the system is activated (from the hand operated valve), the hydraulic fluid will flow through the pipes to the cylinder. This will create a pressure that will force the piston to move in the opposite direction.
That is, it will move the piston downwards. Assuming the hydraulic fluid enters the cylinder through the upper section.
As a result, hydraulic fluid in the lower part of the piston will be forced out of the hydraulic cylinder. It will flow through the pipes back to the reservoir.
This is due to the pressure build up.
In the next cycle, the hydraulic fluid from the pump will flow to the opposite side of the cylinder (where the piston had moved in the first cycle). This pushes the piston up, and the fluid in the other portion of the cylinder will be pushed out of the cylinder back to the tank.
This will result in an up and down movement of the piston, creating a hydraulic power based on the Pascal’s laws.
In the cylinder, hydraulic actuators convert the hydraulic energy into mechanical energy, i.e. a linear motion.
This is how you can create a hydraulic power.
However, before I conclude this section, let’s review some aspects of the hydraulic power.

Hydraulic systems have a high power density. Therefore, the system designers have the freedom to install both pumps and actuators in any convenient location.
You’ll find that hydraulic pumps have a power density, which is ten times greater than that of the electric motor.
To calculate hydraulic power, you can use the following formula:
The theoretical power
Hydraulic power (watts)=Pressure (Pa)×Flow rate (m^3/s)
At this point, you can explain how to generate a hydraulic power.
So far, I have mentioned a number hydraulic power pack components, especially in this chapter. Therefore, it will appropriate if we discuss all these components of the hydraulic system.
This is what I am going to do in Chapter three.

I will make the entire discussion simple and easy to understand. This is because you need to evaluate every component before buying the hydraulic power unit.

An electric motor is an electro-mechanical device that converts and electric energy to mechanical energy. That is, it converts electrical energy to magnetic energy then to rotational force.
Broadly, motors are classified in three main categories:
1. DC motors
Electric motors into this category include: shunt motors, separately excited motors, series motors, permanent magnet DC motors and compound motors.
2. AC motors
These electric motors include induction and synchronous motors. The induction motors are classified further as either single phase induction motors or three phase induction motors.
3. Others
Examples of motors in this category include: stepper motors, brushless DC motors, hysteresis motors, reluctance motors and universal motors.
For the scope of this hydraulic power pack eBook, I will focus on AC and DC motors.
In a hydraulic circuit, electric motors convert the electrical energy into a rotational force that drives the pump gear. You’ll learn more about pump gears in section 3.2 of this chapter.
For now, let’s focus on the different types of motors in hydraulic power pack circuits.

3.1.1 DC Motors

The electrical DC motors convert direct current into a rotational mechanical energy. These motors use a direct power supply whose voltage may vary from DC12V, DC24V, DC48V or DC96V; depending on the design specification of the hydraulic power pack system.

These motors are common in most micro or mini hydraulic power packs. This is because the DC power supply is portable thus, a perfect choice for mobile of portable hydraulic equipment.
You’ll find that most people opt for the DC hydraulic power packs.

1) How DC Motors Work

These motors have the following key parts:

• A stator that provides the magnetic field. For most portable equipment, the stator is a permanent magnet.
• An armature (also referred to as the rotor in this case) that connects to a DC power supply via commutator rings. It’s a coil that conducts electrical energy.

As the current flows through the coil, an electromagnetic force is induced. This causes the coil to rotate. Of course, this is according to the Lorentz law.
When the coil is perpendicular to magnetic flux, the torque action will be zero. Therefore, to ensure smooth operation, there should be more conductor coils.
In practical applications, a DC motor has more rotor loops with different pairs of commutators. The armature loops are always in a slot of highly permeable steel layers.
For large DC motors that are commonly found in large hydraulic systems, the electric motor manufacturers use electromagnet instead of permanent magnets.
That is, the field coil of the electromagnet is powered from the DC source that powers the armature. Depending on the type of connection, you’ll have either a shunt or series DC motor.
The complexity of the design will depend on the type load the motor should drive. In the case of the hydraulic power packs, we have a hydraulic pump as the load.

2) Why Use DC Motors in Hydraulic Pump Applications

Here are some of the reasons why DC motors are common in pump applications:

• DC motors have variable speed control
• They have a high starting torque
• DC motors have good transient response
• High efficiency and power density
• Less maintenance
• Simple and compact design
• Better thermal properties and constant magnetic field

In the recent past, a number of hydraulic power pack manufacturers have adopted the permanent magnet and brushless DC motors for most pump applications. The brushed wound field DC motors are still common in some hydraulic applications.

3) Common Specifications of DC Motors for Hydraulic Power Packs

For a DC motor specification purposes, you need to consider the following key aspects:

• Voltage (DC 12V/24V)
• Power (500w-3kw)
• Duty (S3)
• Motor Rotation: CW, CCW, or Bi-Rotation
• Speed (3000RPM)
• Ingress protection (IP54)
• Fan (up 3kw will have a fan)

You can follow this link to read more about DC motors.

3.1.2 AC Motors

Alternatively, you may also opt for AC hydraulic power packs. Unlike the DC hydraulic power packs, this equipment uses an alternating current (AC).
The AC motors are such that they convert an alternating electrical energy into a rotating mechanical energy. Normally, when you’re designing AC electric motors, you need to consider the AC voltage and frequency of the AC power grid.

These two parameters may vary from one region to another. For instance, in Canada, the residential voltage is 120V, 60Hz while in the United Kingdom it is 230V, 50Hz.
Can you see the difference?
In short, before you purchase an AC hydraulic power pack, you need to consider your grid supply.
Now that you’ve learnt all vital aspects about the DC motors, it will be appropriate to know the difference between these two motors.

1) Differences between AC and DC Motors

Here are the main differences between AC and DC motors:

• Source of power

The AC motors are powered with an alternating current (AC) while the DC motors are powered with a direct current (DC).

• Construction of the electric motors

DC wound field motors have carbon brushes and commutators while the AC motors do not have the carbon brushes.

• Varying speed of the motor

By varying the current in the armature windings, you can easily control the speed of a DC motor. On the other hand, you can only control the speed of an AC motor by varying its frequency.
Most AC motors in industrial setups use variable frequency drives (VFDs).

2) How an AC Motor Works

Quite a number of AC hydraulic power packs use induction motors. The most common types of induction motors are:

• Three phase induction AC motors – requires three power phases
• Single phase induction AC motors – requires one power phase

The induction motors are also called the asynchronous motors.

3) Synchronous AC Motors

Alternatively, you may also opt a synchronous AC motor. In a synchronous motor, the rotation of the shaft is synchronized with the frequency of the supply current.
In the synchronous motors, the magnetic field is generated by the current passing through the sip rings. Normally, the synchronous motors run faster

4) Asynchronous AC Motors

The stator has coils. When you supply with an alternating current produces a rotating magnetic field.
The varying magnetic field will induce electricity in the rotor bars due to electromagnetic induction. Since current carrying bars are immersed in a magnetic field, this produces a force that rotates the rotor.
It is this rotating shaft that you’ll connect to the hydraulic pump

5) Advantages of AC Motors

The main advantages of AC motors include:

• High power output suitable for industrial applications
• They are cheap to construct and maintain
• Rugged and easy to maintain

6) Common Specifications of the AC Motor

Before you buy an AC motor, you need to check the following specifications.

• Voltage (110v, 220v, 380v, 415v)
• Power (370w-7.5kw)
• Frequency (50HZ, 60HZ)
• Duty (S1, S6)
• Pole (2Pole 3000RPM, 4Pole 1500RPM)
• Ingress Protection (IP44, IP45)
• Insulation Class: B

For more information about AC motors you can read: AC Motors: General Principles of Operation.

A hydraulic pump is a device that converts the mechanical energy from the motor (rotary motion) into a hydraulic energy. The output shaft from the electric motor is coupled to the shaft of the hydraulic pump.
As the pump rotates, it creates a pressure difference between its inlet and outlet. This pressure difference helps the pump to draw hydraulic fluid from the tank.
It then pushes the hydraulic fluid through the tubes/pipes to the hydraulic cylinder parts or hydraulic motor. In this section, I will focus on the following types of hydraulic pumps:

• Gear pumps
• Piston pumps
• Vane pumps

As you’ll realize in sections 3.2.1, 3.2.2 and 3.2.3, this classification is based on the structural design of these pumps. In each category, I will:

• Explain the working principle of the pump
• List the sub-categories of the pumps
• State the advantages and disadvantages

This information will help you to choose the right pump for your hydraulic system.

3.2.1 Hydraulic Gear Pump

The hydraulic gear pumps are rotary positive displacement pumps that use meshing gears to pump fluids.
As the gears rotate, they create a suction effect at the pump’s inlet and the fluid is drawn into the pump chamber. The rotation directs the hydraulic fluid between the teeth of the gears and the walls of the pump and finally to the output.

In most cases, it is one shaft of the gear that is coupled to the electric motor. Thus, the movement of the second gear (driven gear) occurs as the other gear (driving gear) engages it when the pump is operating.
Normally, as the fluid travels through the gears (from the inlet to outlet), its volume decreases causing a buildup in pressure.

Some of the most common types of gears in these pumps include:

• Spur gears
• Helical gears
• Herringbone gears

The herringbone and helical gears in these hydraulic pumps offer a smooth flow than spur gears. The flow rate of these gears is determined by a number of features such as:

• Size of volume between the gear teeth
• Speed of rotation
• Amount of slip flow

1) Types of Hydraulic Gear Pumps

There are two main types of gear pumps:

• External gear pumps

In these gears, the hydraulic fluid flows through the inlet, then into the teeth and to the outer periphery of the rotating gears.

• Internal gear pumps

These hydraulic pumps have an externally-cut teeth that are contained in and meshed another gear that has an internally-cut teeth. Liquid is drawn when the gears come out of mesh and is discharged when the gears mesh together.

2) The Advantages and Disadvantages of Gear Pumps

Before choosing these gears for your hydraulic systems, it is important that you consider the following:
The advantages of hydraulic gear pumps

• Easy to maintain, control and operate, i.e. increasing the speed will automatically increase the output.
• They are self-priming
• Produces a steady flow
• Can pump high viscous fluids
• You can operate them at very low speeds
• Are compact in size
• Have a simple construction and design

The disadvantages of hydraulic gear pumps

• Output efficiency, reduces due to wear and tear of gear teeth
• You cannot run the pumps dry
• Cannot handle fluids with suspended fluids

3) Common Specifications of the Target Gear Pumps

Here are some common specifications of this hydraulic equipment:

• Size (0.5 small, 1.0 big)
• Material (Aluminum, Steel)
• Displacement (small 0.19-2.0cc/r; big 0.75-8.0cc/r)
• Rotation: CW, CCW, Bi-Direction
• Max Pressure: 160BAR, 180BAR, 210BAR or etc.
• Shaft (Types) 9T Spline
• Dimension and mounting size

In most cases, you’ll find a number of hydraulic power packs with hydraulic gear pumps.

3.2.2 Hydraulic Piston Pump

A hydraulic piston pump is also an example of a positive displacement pump. They are also called the well service pumps.
Their working principle of a piston pump is simple:
These pumps use their contracting and expanding cavities to move hydraulic fluids from the cylinder to the tubes. This is possible with the help of an electric motor that creates motion, pistons and check valves.
The pistons exert pressure on the fluid while the check valves ensures the fluid flows in the right direction. Also, the number of pistons will also depend on the number of pistons.

Hydraulic pistons undergo a reciprocating motion (moving up and down or back and forth), thereby building a pressure that forces the fluid through the tubes.
Of course, this movement is due to the differential pressure due to the movement of the pistons of the pump.
Depending on the type of hydraulic machines you intend to operate, you can opt for an electric motor operated piston pump or hydraulic hand pump.

Hand pumps are mainly used in simple processes and tasks that are not labor intensive.

1) Types of hydraulic piston pumps

The main types of piston pumps include:

• Axial Piston Pump

It has a cylindrical block with pistons that move in the direction of its centerline. They have simple designs and guarantee reliable operation.

• Radial Piston Pump

Its pistons are attached to cylindrical block, forming a wheel like structure. The rotation of the cylindrical block causes a back and forth motion within the pump.
They are popular for their high efficiency, low noise level and high loads even at low speeds.
Hydraulic piston pumps can further be classified as single acting, double acting, simplex, duplex and multiplex piston pumps.
Before you choose these pumps for a specific application, it is important to consider the following:

2) The Advantages of Hydraulic Piston Pumps

Four main advantages of these pumps include:

• You can operate them within a wide pressure range – from low to very high pressure.
• Controlling pressure does not affect the fluid flow rate.
• Its performance does not solely depend on both pressure and flow rate.
• It can pump a wide range of fluids be it viscous, abrasive or slurries. However, you’ll modify the valves to suit such applications.

3) The Disadvantages of Hydraulic Piston Pumps

The main disadvantages of these pumps include:

• It’s difficult to achieve a smooth, fluid flow as it keeps on pulsating.
• They come with high operating and maintenance costs.
• These pumps are heavy and bulky

4) Common Specifications of the Target Piston Pumps

Here are key specifications of hydraulic piston pumps you should consider:

• Compact size
• Material
• Displacement
• Torque
• Operating pressures
• Dimension

3.2.3 Hydraulic Vane Pump

A hydraulic vane pump is a positive displacement pump. They are suitable for pumping low viscosity fluids.
These pumps improve flow rate by reducing the internal mechanical losses and damping. It is a common phenomenon in some special designs.
The working principle of vane pumps is based on the fact that:
An electric motor is coupled to the pump rotor to create a rotary motion. As the rotor rotates, the fluid enters the pump.
This fluid flows into the hydraulic vane pump chambers. The volume of the vane chambers at the inlet sections is larger than that at the outlet section of the pump.
The decrease in volume helps the fluid to develop a high pressure as it exits the pump.
As the rotor rotates, the pump vanes tend to move outwards. This is due to the centrifugal force and the symmetrical shape of the pump casing.
In the inlet, the vanes create a vacuum, causing a pressure difference thus, it draws fluid into the pump.

1) Types of Vane Pumps

Broadly, you can classify vane pumps as:

• Fixed displacement cane pumps

These pumps can be classified further as either unbalanced or balanced vane pumps. Most opt for the balanced vane pumps because they have better speed ratings, high pressure and increased bearing lifetime.

• Variable displacement vane pumps

In these pumps, you can vary the position of the cam ring relative to the rotor. With this, you vary the distance by which the vane extends.
This arrangement makes it possible to have a variable volume in these vane pumps.
Like other hydraulic pumps, the vane pumps may not be suitable for certain pumping applications. Here are the main advantages and disadvantages of these pumps.

2) The Advantages of Hydraulic Vane Pumps

The five main advantages include:

• They can pump less viscous fluids at high pressure.
• Wear and tear is reduced due to the vane extension.
• You can run them dry thou for a short period.
• They develop good vacuum.
• The design minimizes leakages that are common in gear pumps

3) The Disadvantage of Vane Pumps

These include:

• They have a complex structural design.
• Not suitable for fluids with high viscosity.
• They cannot pump fluids with debris or abrasives

4) Common Specifications of the Target Vane Pump

Before you purchase these pumps, you need to consider the following:

• Dimension
• Type of materials for these main sections:
  1. Shaft seal – Component mechanical seals, industry-standard cartridge mechanical seals, and magnetic-driven pumps.
  2. Vane, pushrods – Carbon graphite.
  3. Externals (head, casing) – Cast iron, ductile iron, steel, and stainless steel.
  4. End Plates – Carbon graphite.
  5. Packing – Available from some vendors, but not usually recommended for thin liquid service
• Displacement
• Pressure
• Shaft

With these two main components of the hydraulic power pack (electric motor and pump), your systems should draw the hydraulic fluid, ready to supply it to the circuit.
Next, let’s explore the basic components that make the other section of the hydraulic circuit.

A hydraulic manifold helps to regulate the fluid flow, pressure and flow direction in hydraulic systems. It acts a junction between the hydraulic pump and hydraulic actuators.
The hydraulic manifold design may vary depending on the types and number of control components. With the help of various hydraulic manifold valves, you can easily monitor and control the fluid flow.
In this section, I will discuss the following types of hydraulic manifolds:

• Central manifold
• Stacked manifold block
• Standard manifold block
• Customized manifold block

As you’ll realize later in this section, these hydraulic manifold blocks mainly vary depending on how hydraulic valves are interconnected to each other.

1) Advantages of Hydraulic Manifold Blocks

These include:

• To help monitor and control fluid flow, pressure and flow direction.
• Creates a logical installation of hydraulic circuits by eliminating clutter.
• Occupies a small space since all valves are assembled together – compact design.
• Reduces hydraulic system assembly time and labor.
• Reduces the number of leaking points and pressure drop.

2) Criteria for Choosing the Right Hydraulic Manifold Block

In case you’re planning to buy a hydraulic manifold your hydraulic system, here key factors to consider:

• Type of materials and finish
• Electrical voltage and connection
• Duty cycle
• Number and type of valves
• Temperature
• Type of hydraulic fluid
• Seal material
• Maximum working pressure
• Mounting position
• Port sizes and location

Below are some of the most common types of hydraulic manifold blocks in hydraulic power packs.

3.3.1 Central Manifold

The hydraulic central manifold has several multiple options you can use for integral solenoid, mechanical operated hydraulic valves and an interface for custom designed valves.
This hydraulic center block has several mounting holes for:

• Power unit
• Hydraulic cartridge
• Gear pump
• Oil suction pipe
• Oil return pipe
• Oil port for hose
• Stacking block

Furthermore, you can use the space within the valve block for the built-in valves.

You will learn more about the structural design of this central manifold in chapter four. There is a complete schematic diagram.
Common Specifications of the Target Central Manifold
Always remember to review the following specifications:

• Material
• Types:
  1. i. Single acting
  2. ii. Double acting
• Cartridge hole – check valve; relief valve; release valve; needle valve
• Oil Port Types: BSPP(G); NPT; SAE

3.3.2 Stacked Manifold Block

For more complex and flexible functionalities, you can use the hydraulic stacked manifold. This helps to combine multiple functions into one assembly such as reducing the possibility of pressure drop.
This is actually the main reason why you should consider a stacked manifold block as an extra section of the hydraulic center block. You can use it when the space in the central manifold cannot hold more valves or large size cartridge valves.

Common Specifications of the Target Stacked Manifold Block
You should consider the following key options:

• Material
• Types:
  1. For Stacking Valve
  2. For Cartridge Valve

3.3.3 Standard Manifold Block

Target has delivered thousands hydraulic power units for different applications around the world. These include a series of standard hydraulic manifolds that are commonly used in most hydraulic power packs.

3.3.4 Customize Hydraulic Manifold

At times, the standard hydraulic power packs may not meet the specific requirements of your applications. In such cases, you should opt for customized hydraulic manifold blocks that meet your specific requirements

Apart from the hydraulic manifold blocks, I need to introduce you to the actual components that control the hydraulic fluid. This is the hydraulic valves.

Valves are devices that control the flow of fluids in hydraulic systems. They regulate flow by cutting-off, diverting, providing an overflow relief and preventing reverse flow of the hydraulic fluid, among other functions.
In the hydraulic power packs, it is the hydraulic valves that direct the fluid to and from the cylinder.
There are very many hydraulics valves available in the market. However, for the scope of this eBook, I will focus on the following:

• Hydraulic check valves
• Hydraulic relief valves
• Hydraulic cartridge solenoid valves/release valves
• Hydraulic needle valve/throttle valves
• Hydraulic directional control valves
• Hydraulic modular valves

All these valves have unique features, designs and performance requirements, making them suitable for different applications.
What do I mean by this?
Take for instance, a hydraulic cartridge valves.

As you can see, there are many types of hydraulic cartridge valves available in the market. These valves are suitable for high flow rates and leak free control systems such as hydraulic power packs.
So, it is important that you choose a valve that meets the specific requirements of a given application.

3.4.1 Check Valves

A hydraulic check valve allows fluid to flow through it in one direction, i.e. it prevents a reverse flow. For this reason, it is also referred to as one-way valve or non-return valve.
Most check valves in the market use either a poppet or light spring to control fluid flow. However, different check valve manufacturers may use varying approaches, depending on the intended application.
Still, you can classify these types of check valves as either a ball valve or cone valve. The latter uses a different movable part to block the flow.
Since the check valves provide unidirectional flow, thereby providing a sealing against the reverse flow, it is advisable that you install them on the outlet side of the hydraulic pump. Below, is an image showing how a hydraulic check ball valve functions:

In hydraulic circuit diagrams, you can represent these valves using their unique symbol:

However, in reality, this is how a hydraulic check valve looks like:

In hydraulic power pack circuits, you’ll mount the internal check valve in the block, while the external check valve on mounting hole found on the surface of the valve block.
Manufactures use different materials to produce check valves such as zinc plated carbon body and hardened stainless in-line poppet. This aims to provide a long-lasting metal-to-metal seal.
At times, hydraulic power pack manufacturing companies may include a pilot operated check valve. You can control these valves using fluids from other valves.
A hydraulic pilot-operated check valve is unique in the sense that; they allow hydraulic fluid to flow in one direction, but, you can still disable them using a pilot pressure.
To open this valve, you’ll need an inlet pressure pA, pilot pressure pX or at times, you may need both. You can express the amount of force due to this as:

3.4.2 Relief Valves

In hydraulic circuits, relief valves protect the downstream circuits from over pressurization. They are a good example of a safety valve and you may also refer to them as pressure relief valves (PRV).
There are many types of pressure relief valves that vary in design and specifications. A good example is the pilot-operated relief valve.
During the period of work cycles, these pilot operated relief valves unload the pump at low pressure. Another important classification criteria is the type of material.
A number of adjustable hydraulic pressure relief valves are manufactured from zinc plated carbon steel bodies. They have hardened stainless steel sealing components.
In circuits the hydraulic valve symbol is as shown below:

Most hydraulic valves come with a preset pressure (specific cracking pressure). They are either adjustable or feature a tamper proof wire.
The tamper proof wire prevents field adjustment. Their principle of operation can be illustrated by the image below:

You’ll find that when the pressure is reduced within 25% of the set point, the valve will automatically reseal. Below is the actual image of a hydraulic relief valve:

Parameters to Consider When Selecting a Pressure Relief Valve
Below are seven crucial parameters you need to consider when buying a pressure valve:

• Pressure rating; it should be compatible with your hydraulic power pack system pressure.
• Temperature rating; consider the fluid and environmental temperature.
• Type of material; should be corrosion resistant and not affected by fluctuating fluid temperature.
• Flow rate; consider maximum flow when the valve is fully open and pump operating at full capacity.
• Reset pressure; this is the pressure where the relief valve will close once opened.
• Relief setting; this is always above the system normal operating pressure (about 5 to 10%).
• Relief pressure range; this is the minimum and the maximum pressure where you’ll require the valve to open and close.

Other vital aspects that will affect the operation of the relief valve are clearances/seals, failure mode and hysteresis.

3.4.3 Release Valves/ hydraulic cartridge solenoid valves

A release valve or hydraulic cartridge solenoid valves are examples of directional control valves. You can use these valves to:

• Stop fluid flow
• Allow fluid flow
• Change direction of fluid flow

In most applications, a hydraulic release valve also means a 2 way 2 position hydraulic cartridge solenoid valve. Solenoid valves are electromechanical operated valves.
Such valves have a fast and a safe switching mechanism. They are also: reliable, durable, compact in design and offer low control power. Below are examples of hydraulic release valves:

In hydraulic circuits, they are represented as shown below:

Since these directional control valves have a solenoid, their control mechanism depends on electrical energy. In most cases, you can refer to them as a variable force solenoid.
This is because, their pressure control is either inversely or directly proportional to the electric signal (current or voltage).
Without the electric energy, these valves operate in only one-way state. That is, the hydraulic fluid can only flow in one direction.
It’s the electric current that makes it a two-way valve. Where, it will allow the hydraulic fluid to return to the tank, thereby, releasing the load of the cylinder.
Owing to the varying circuit designs of directional control valves, you’ll find quite a number of hydraulic control valves and valve block mounting dimensions.

Broadly, the main types of solenoid valves include:
a. Solenoid normally closed valves
In these circuits, the coil voltage may vary depending on the design. The most common configurations include: DC12V, DC24V, AC24V and AC220V.
The type of coil also varies. These may include: Hirschmann, double lead or waterproof double Lead
b. Manual release double check valves
A good example of the solenoid valve with manual override. These are common in car lifting equipment where you can decide to operate the solenoid valve manually.

Normally, you can adjust hydraulic solenoid valve depending on the type of control mechanism of a specific application. Moreover, the complexity of a directional control valve will also depend on the specific hydraulic system you intend to control.
You can go for a:

• 2-way directional control valve
• 3-way directional control valve
• 4-way directional control valve

You can learn more about how to use and their circuit diagrams here: Directional Control Valves.

3.4.4 Needle Valve/Throttle

These are valves that allow for precise fluid control and are mainly designed for low flow rates. Needle valves have a slender and tapered point towards the valve stem that blocks or restricts the flow.
In most hydraulic circuits, you can install them near delicate gauges that may get damaged in case of a sudden pressure surge. Also, you can use these throttle valves in the pipes returning oil back to the tank.
Needle valves can increase, decrease or completely shut off fluid flow. In throttle control, the needle valves are preferred compared to ball valves.
In hydraulic circuits, you can represent throttle valves using this symbol:

This is how the needle valves look like:

Factors for Consider When Choosing Needle Valves
For any hydraulic fluid control, here are the key factors you need to consider:

• Pressure ratings

Needle valves can handle a wide range of pressures. Depending on the nature of the hydraulic fluid system, a needle valve can handle the pressures that range from 5,000 to 6,000 psi.
There are high pressure needle valves that can handle pressure up to 10,000 psi.

• Size of the Valve

These valves are available in different metric sizes that range between 2 and 11mm. Also, there are the standard sizes that range from 1/8” to 1”.

• Operating temperature of the valve

Here, you need to consider valves with polytetrafluoroethylene (PTFE) as it provides additional resistance an endurance to high temperature. The working temperature range is -65°F to 450°F.
Another option is the polyether ether ketone (PEEK) needle valves. This increases the working temperature to 600°F.
Remember, PEEK and PTFE are the most common packing materials in needle valves.

• Type of material

Some of the most common materials include carbon steel, stainless steel or brass. Each material has unique physical and chemical properties making them suitable for specific hydraulic applications.
For instance, a stainless steel needle valve is a perfect choice for chemical processing applications and circuit that are susceptible to corrosion.

3.4.5 Directional Control Valves

In section 3.4.3 of this chapter, I had discussed quite a number of aspects of a directional control valve. Again, in this section, I will have a quick overview of other types of directional control valves.
A directional control valve directs hydraulic fluid into different paths. They have a spool that you can control either mechanically or electrically.
In the recent past, manufacturers have been opting for electric control valves. Here is how the directional control valves work:

Clearly, from this electrically operated valve, their designs tend to be more complex than the release valves. You may find a 4 way 3 position directional control valve or a 2 way 2 position control valve.
The complexity of the design will depend on the specific application of the directional valve in a hydraulic control circuit. In hydraulic circuits, the directional control valve symbol is:

Classification of Hydraulic Directional Control Valves

Broadly, all the available directional control valves fall into these 4 categories:

• Number of ports

This refers to the number of ports that allow fluid to flow in and out of the directional valve. Depending on the number of ports you may have a 2 way 2 position valve, 4 way 3 position valve, etc.

• Number of positions

This is the number of both normal and working positions that the directional valve spool can take. It can be 2 positions, 3 positions, etc.
You can see this clearly from the previous examples.

• Actuating methods

There are three main actuating methods and they include manual, electrical and mechanical.
Examples of manual actuated valves include manual release double check that are common in car lifting equipment and manual directional control valves.
An electrically actuated directional control valve includes solenoid directional valves and solenoid pilot operated valves.
These solenoid valves come with varying power options such as DC12V, DC24V, AC24V and AC220V.

• Types of spool

You can go for a directional control valve with a sliding or rotary spool. The sliding spools are cylindrical in nature while the rotary spools has a spherical shape.

3.4.6 Modular Valves

Modular valves provide a wide range of mounting options in hydraulic circuits. They have a number of mounting holes, valves and loops compared to cartridge valves.
You can fit them in any system to fulfill the specific hydraulic circuit requirements. At the moment, there is a wide range of modular valves available in the market such as pilot operated check valves, flow control valves, pressure reducing valves and counterbalance valves.
Take for instance the Target’s hydraulic lift valve. These valves offer a perfect solution is all lifting solutions.

They have a unique design to control single acting cylinders. These modular valves function such that they offer superior control mechanism when raising and lowering loads.
With that in mind, we can explore other types of modular valves you can use for your hydraulic power packs.

• Flow control valves

The hydraulic flow valves are available in a wide range of configurations and designs, depending on the functional purposes of each valve. A good example is a modular flow control valve with a directional control valve and a sub plate.

Flow control valves may have different ports such as A, B or A & B.

• Modular pilot operated check valve

Some of the most common valves include:

1. A port Control
2. B port Control
3. A&B port Control (hydraulic lock)

Here is how a pilot operated check valve looks like:

These pilot operated check valves are suitable for applications where a remotely-controlled checking function or high –flow rate is required. They provide an automatic stopping.
Other options available may include pressure controlled, solenoid controlled, single pressure controlled, dual internal pressure controlled and dual solenoid controlled check valves.

• Pressure reducing valve

This is yet another popular hydraulic pressure valve. Below is a picture of pressure reducing valve:

In most cases, you can specify modular reducing valves depending on the maximum operating pressure and maximum flow rate.

• Counterbalance Valves

You can use counterbalance valves to reduce pressure on “A” port and “B” port. They are mainly manufactured from cast iron and the specification criteria is based on maximum pressure, connecting port and maximum flow rate.
As you can see, there are very many types of modular valves. Therefore, you need to review the manufacturer’s data sheet to choose a modular design that best suits your hydraulic system.

Throughout this section, I believe you have noted that there are very many types of hydraulic valves. Always choose one that best suits your hydraulic power pack.
Remember, with an appropriate valve, you can have full control of the fluid flowing through the hydraulic pipes. Now, let’s discuss the next component of a hydraulic power pack.

A hydraulic tank is a container that holds the fluid that you’ll supply to the system to do the work. At times, you may refer to it as a hydraulic reservoir.
Hydraulic oil tanks for power pack units come in a wide range of shapes, sizes and materials. For the scope of this eBook, I will focus on the following:

• Hydraulic plastic tanks
• Hydraulic steel tanks
• Components of a hydraulic

Generally, hydraulic reservoir stores and helps in the recovery process.
Let’s look at these three key items in details.

3.5.1 Plastic Tanks

Quite a number of hydraulic plastic tanks are made from polypropylene (PP). This is a special oil tank material that is resistant to corrosion, low temperature, high temperature, acid-alkaline solutions and solar radiation.
Most manufacturers use an injection molding technique that results in a light weight and strong hydraulic fluid tank. The tank can withstand high pressure and resistant to diverse weather conditions.
This makes plastic tanks cost effective and popular in most hydraulic power packs.

The key features of power pack, hydraulic tanks include:

• Surface color

Most of them come in white color, so users can easily see the level of oil in the tank. Therefore, you don’t have to use a liquid meter to know the exact level of the fluid.
Of course other colors are also available.

• Size of the hydraulic plastic tank

The size may vary depending on both design and size of the hydraulic power pack. The volume of the tank should be large enough to allow for all hydraulic fluids in the pipes to drain in the tank.
Therefore, you’ll find that the hydraulic fuel tank size may vary depending on the hydraulic equipment such as hydraulic stacker, hydraulic lifting equipment, hydraulic dock ramp, hydraulic scissor lift, etc.
The volume of the tank may vary from 1.0 liters to 24 liters while its neck size is 94mm , 120mm or 123mm.
Apart from these, you can mount it in either horizontal or vertical position. It has a mounting hole that is round, prolate ellipse or unclosed circle.

3.5.2 Steel Tanks

Like the plastic hydraulic reservoir tanks, the hydraulic steel tanks are available in a wide range of sizes and designs. Unfortunately, for these hydraulic power pack steel tanks, you’ll need a liquid meter to determine the level of hydraulic fluid.
The steel tanks are also heavier than plastic tanks. They are mainly manufactured from stainless steel.
At times, you may also find iron hydraulic tanks.
They come in a wide range of colors and customized shapes/design. You may opt for a black, red or blue hydraulic tank reservoir.
These tanks are mainly fabricated by punching and welding. This results in a strong and durable tank, which is resistant to a wide range of weather conditions.
Basically, these tanks are specifically manufactured to resist high and low temperature conditions. They ensure the properties of hydraulic fluid remains the same at all times.

Properties of hydraulic steel tanks

Some of the key features of these hydraulic tanks include:

• The shape is either round or square
• Volume may range from 1.2L to 30L; bespoke also available
• Mounting position is either vertical or horizontal
• Tank neck size is 94mm by 120mm by 123mm
• Mounting hole maybe round; prolate ellipse; unclosed circle

3.5.3 Hydraulic Tank Components

As you have seen from the pictures of the two tanks listed above, it is clear that they have three main components:
a. Air breather
This allows air to get into the tank, thereby protecting the tank from atmospheric pressure. Remember, as the gear pump rotates it creates a vacuum that forces hydraulic fluid into it.
b. Steel plug
By opening the steel plug, you can drain the hydraulic oil from the tank. It seals the tank’s outlet.
c. Steel tank neck
You will mount hydraulic power pack to the other customized steel tank through the steel tank neck. So, you can mount one or two or more power packs on one steel, square customized steel tank.

In this section, I am going to discuss the various parts that interconnect the major hydraulic components such as tanks, pumps, electric motors, etc.
The connecting parts include couplings, cables and tubes.

3.6.1 Couplings

A coupling is the main device you’ll use to connect your electric motor and hydraulic pump. That is, you’ll connect the shaft of your motor to that of the hydraulic pump.

A shaft coupling helps to transmit the rotational power from the motor to the hydraulic pump.

Factors to Consider when Choosing the Right Coupling

Before you choose the right coupling mechanism, you need to consider the following:

• Parallel misalignment
• Angular misalignment
• End float
• Torsional flexibility

Types of Coupling

The type of coupling will depend on the position of your electric motor relative to that of the hydraulic pump. Some of the most common types of coupling include:

• Flexible coupling; this is when the coupling can handle both parallel and angular misalignment.
• Rigid coupling/compensation coupling; mainly used in applications where shafts are coaxial to each other.

In most cases, you’ll be required to specify these types of couplings based on the type of spine and length.

3.6.2 Cable

You’ll use electric cables to power the motor. That is, you have to connect the starter or power source to the motor.

You have to choose the right cables based on the rating of the electric motor.

3.6.3 Fittings, tubes, hoses and connections

To ensure there is a seamless flow of hydraulic fluid from the tank to the cylinder, you’ll need the following:

1. Fittings; this connects the hose to the outlet of the manifold if they don’t match.
2. Tubes; it functions like a hose, but tube is made from steel so it is inflexible.
3. Hoses; it’s flexible and connects the hydraulic power pack with the hydraulic actuator.
4. Connections; they connect the hose or tube to the hydraulic actuator.

Hydraulic pipes and filters play an integral role in hydraulic power pack systems. In this sub-section, you’re going to learn about:

• Hydraulic suction pipe
• Hydraulic return pipe
• Hydraulic filers
• Hydraulic pipes that keep valves
• Seals

3.7.1 Hydraulic suction pipe

As the hydraulic pump rotates, it creates a pressure difference, hence, the fluid flows to the pump. A hydraulic suction pipe is the pipe that connects the tank and the pump.
It’s through this pipe that oil reaches the pump. Common specifications of hydraulic suction pipes are:

1. Connect thread size (G3/8)
2. Shape (curve; Straight)
3. Length: – Curve: 73mm, 29mm
   1. Straight: 120mm, 180mm, 280mm, 320mm

3.7.2 Hydraulic return pipe

This is the pipe that returns the oil to the hydraulic tank. Common specifications include:

1. Connect thread size (M12*1)
2. Shape (Straight)
3. Length: 120mm,180mm,280mm,320mm

3.7.3 Hydraulic Filters

Hydraulic filters remove debris or impurities in the oil before it is suctioned through the hydraulic pipe to the pump. It helps to keep the hydraulic system clean.
These filters come in different sizes and configurations with some equipped with magnet to remove metallic parts from the hydraulic fluid. This prevents clogging.
Hydraulic filter’s specification is based on:

1. Connect thread size (G3/8)
2. External diameter (43mm;65mm;70mm)

3.7.4 Hydraulic Pipes that keep valves

There are valves you cannot install in the hydraulic block. Also, you may find that, there is no extra space to install them on the outside section.
In such situations, there only option is to install such valves in the pipe system. These are what we call hydraulic pipes that keep valves.

Some of the most common types of seals include mechanical seals and O-ring. These are important accessories that prevent oil spillage.
They are commonly used in power units and joints. Most of them are made from synthetic rubbers.
Some of the main factors to consider when selecting seals include:

• Working temperature and pressure
• Chemical compatibility
• Lubrication requirements
• Size
• Cost

Again, you have to follow the recommended instructions from the manufacturers to prevent seal failure.

These are basic components of hydraulic power packs that depend on electrical signals to send commands to the system. In this subsection, you’ll learn about three major components:

• Cable remote-push button pendant
• Wireless remote
• Starter relay
• Cable
• Battery

3.9.1 Cable Remote-push Button Pendant

This remote pendant is a button controlled and it has a wire (usually 4 meter) that connects to the solenoid valve, and can control the solenoid valve by DC12V, and DC24V.
The cable remote-push button pendant is water-proof and shock resistant.
You can click here to learn how to wire the hydraulic power pack. Below is a picture of a remote button.

This is how you can connect it to a hydraulic power pack system:

To operate this accessory successfully, you need to understand the following options available:

• 2 Buttons Remote

You can use this for single acting mini hydraulic power packs. It has three wires that are 4 meters in length.

• 2 buttons Remote with lock

Commonly used for single / double acting hydraulic system. There was a key you can lock this remote away from battery, so, nobody can operating power pack without this key. It has four wires, which are 4 meters

• 4 buttons Remote

You can use this for dual double acting mini hydraulic power pack. It has four remote buttons with 6 wires that are 4 meters.

3.9.2 Wireless Remote

This equipment provides you with a wireless access to the hydraulic power pack. It has a remote wireless transmitter and receiver.
With this wireless remote, your ability to control a power unit is not limited by the length of the wire. It has a remote control range of up to 200 meters.

Its transmitter has a long life battery alongside the battery saver circuit. You can also observe remote operation via a visual indicator light.
The wireless remote is waterproof and rugged to meet the dynamic industry demands.

3.9.3 Starter Relay

Starter relay is an electrical part that connects to the remote, DC motor and DC battery. As the remote operates, the starter relay turns on and let the battery start the DC motor.
A good example is the Trombetta starter relay. It is trusted due to its diverse nature, robust design and reliability.

The key specifications include the following:

• Intermittent Duty:

Carry Current 150 Amps, Inrush 800 Amps
Available in 12 or 24 Volts
This is for high amperage applications. It is unique design makes it long-lasting and resistant to harsh weather conditions.

• Continuous Duty:

Current 150 Amps, Inrush 800 Amps (depending on voltage and design)
Available in 12 volts, 15 volts, 24 volts, 36 volts, and 48 volts
It is specifically designed for electric vehicles and applications that require robust equipment.

3.9.4 Cables

It is these cables that connect the button remote to the starter relay and solenoid valves.
The specification is based on: length, usually 3meters and number of core: 3 PIN or 4 PIN.

3.9.5 Battery

This is the DC power supply of DC hydraulic power pack.

A hydraulic actuator is the mechanical portion that converts hydraulic power into useful mechanical work. This mechanical work can either be linear motion, rotary motion or oscillatory motion.
Broadly, there are a wide range of actuators you can choose for any intended application. These include:

• Valve actuators

A valve actuator refers to the mechanism of opening and closing a valve. Some of the most common types of valve actuators include manual, pneumatic, hydraulic, electric and spring valve actuators.

• Linear actuators

Linear actuators create motion in a straight line. You can create motion using different mechanisms that may involve the use of mechanical, hydraulic, pneumatic, piezoelectric or electro-mechanical actuators.

• Electro-hydraulic actuator

The electro-hydraulic actuators are commonly used in applications that require a high degree of precision. They have self-contained actuators, which are operated only by electric power.
For the scope of this power pack eBook, I will focus on hydraulic actuators.
Let’s have a quick review of the various components of a hydraulic actuator.

1) Hydraulic Cylinder

In chapter 1, section 1.2 (sorts of hydraulic power pack) and section 1.3 (function of hydraulic power), I did discuss all the vital aspects about single acting and double acting hydraulic cylinders.
That is, from the basic parts of hydraulic cylinders to how hydraulic cylinders work. Well, the working principle remains the same.
Maybe, to remind you about what I had discussed earlier, you can watch this video:
https://www.youtube.com/watch?v=-AueLXLVglc
Of course, this is how a hydraulic cylinder looks like:

Just as a reminder, you should know that hydraulic cylinder is an important hydraulic actuator. It converts hydraulic energy into a mechanical energy we use to perform a number of tasks.
This is also evident in chapter 1, section 1.4 (Applications of hydraulic power packs).
As you have learnt earlier, hydraulic power packs are broadly categorized as either single acting hydraulic cylinder or double acting hydraulic cylinder. So, this fact does not change in hydraulic cylinder actuators.
Maybe, a new concept that I didn’t mention in the previous sections is the position-sensing hydraulic cylinder.
About a Position-sensing Hydraulic Cylinder
A position-sensing hydraulic cylinder is used in more advanced systems where it provides an instantaneous analog or digital electronic position feedback information. That is, it indicates the extent of rod extension during any stroke.
Such cylinders may have either an internal or external displacement transducer. However, the internal displacement transducers offer a reliable solution when it comes to this sensing technology.
As you have seen earlier (chapter 1), all these hydraulic power packs have their unique advantages and disadvantages. You will learn more about this in chapter 5.

2) Swashplates

Swash plate angle determines the rate of oil flow from the pump. Normally, you can adjust this angle using a hydraulic control system.
In most cases the speed of the motor is proportional to the swash plate angle. Swash plate is commonly in inline axial piston pumps.

3) Hydraulic Motor

(rotational movement). The amount of mechanical force will depend on the magnitude of hydraulic energy.
That is, a hydraulic motor can generate different magnitude of torque at different pressures. Some of the main applications include hydraulic bicycle and hydraulic hybrid vehicle.
You can watch the video below to understand how hydraulic motor works:

Before it begins to rotate, the hydraulic fluid should provide sufficient torque to turn the motor. The torque that the hydraulic fluid provides can be categorized as:
Breakaway torque
This is the minimum torque you’ll need to start the motor at no load. That is, the hydraulic energy should overcome the internal frictional forces of the motor.
Running torque
It is the sufficient torque that keeps both the hydraulic motor and load rotating.
Starting torque
It’s the torque required to rotate the motor under load.

Types of Hydraulic Motors

The existing hydraulic motors may be classified into four different categories. These include:

1. Hydraulic gear motors; they include hydraulic and epicyclic gear motors.
2. Hydraulic vane motors; main subcategory is balanced vane motor.
3. Hydraulic piston motor; these include axial and radial piston motors.
4. Part-turn actuators such as rotary actuator and rack & pinion actuator.

I have seen most people who tend to confuse hydraulic pumps and hydraulic motors.
The truth is, hydraulic pumps add more energy to the circuit by pushing the fluid while the hydraulic motors act as actuators that change hydraulic energy into rotary motion. Furthermore, hydraulic pumps are coupled to an electric motor.

4) Hydrostatic Transmission

The concept of hydrostatic transmission is based on the fact that, whenever a pump is connected to a prime mover, it generates fluid flow that drives a hydraulic motor. It is this hydraulic motor that is connected to the load.
To make it more versatile, you can make either the pump or motor variable displacement. You can learn more about this concept here: Understanding Hydrostatic Transmissions.

5) Brakes

This is breaking mechanism that uses brake fluid (hydraulic fluid) to stop or control a moving wheel or object. You can review hydraulic power pack applications in chapter one to learn more about this.

Hydraulic fluid is the medium through which power or energy is transferred in hydraulic systems. Some of the most commonly used hydraulic fluids are either mineral or water based solutions.
From the definition of Pascal’s Law, you can clearly tell the main characteristics of and liquid that you can use as a hydraulic oil.

Features of an Ideal Hydraulic Fluid

An ideal hydraulic fluid should possess the following key features:

• Thermal stability
• Long life
• Hydrolytic stability
• Total water rejection
• Low chemical corrosiveness
• Low cost
• High anti-wear characteristics
• Constant viscosity

There are many types of hydraulic oil fluids in the market. At times, it becomes nearly impossible to choose the right hydraulic fluid.
Below are essential hydraulic system parameters you need to consider when choosing a hydraulic fluid:

• Type of hydraulic pumps
• System operating temperature
• Operating cycle
• System operating pressure
• Expected force to be generated
• Control systems such as hydraulic valves.

Basically, these are the basic aspect you need to know about hydraulic fluid. To learn more about these oils then you can click: Engineering Essentials: Hydraulic Fluids.
Now that you’ve known all the components of hydraulic power packs, let’s learn how to design one that meets the specific needs of our applications.
You’ll learn about the basic circuit diagrams in chapter 4.

The design process begins by having a specific performance requirement for every component we would wish to include in our system.
Remember, every hydraulic component listed in chapter 3 will directly affect the design process and the cost.
Moreover, the size of say a cylinder, type of valve or type of a motor will determine the unique performance characteristics of the hydraulic power packs.
This explains the reason why we have micro hydraulic power packs, mini hydraulic power packs, etc.
Let me review the hydraulic power pack design components you need to consider.

The standard design features and performance you need to consider include the following:

1.Motor Pumps

You need to specify the rating and capacity of the hydraulic pumps. They will push the hydraulic fluid in the circuit to do work.
Some of the key calculations for the hydraulic pumps include:
Horsepower required to drive the pump
In this case, you’ll use this simple formula: GPM×PSI×.0007
This is a “rule-of –thumb” calculation. For instance, if your pumps should drive 5gpm at 1,500 psi, then you need a drive motor whose horse power is 5.25kw.
Hydraulic pump displacement needed for GPM of Output Flow:
You’ll determine this using the formula: 231×GPM÷RPM
Thus, assuming displacement of 5 GPM at 1500 RPM, then using the equation above, you’ll get 0.77 cubic inches per revolution.
Pump Output Flow (in Gallons Per Minute):
You can obtain this using the formula: RPM×Pump displacement ÷231
Implying, in case you need to determine the amount of oil that your pump will produce with a displacement of 2.5 cubic inch pump operating at 1200 rpm?
Inserting these into the above equation you get: 12.99 GPM.
Basically, these are the four basic equations you need to know when designing choosing the best pump for your hydraulic power pack.

2. Hydraulic Cylinder Calculations

Below are important hydraulic cylinder equations you need to consider in your design process:
Cylinder Rod End Area (in square inches):
You get this using: Blind end area-Rod area
This implies, you need to determine the area of these sections. Of course, you have to determine geometrical figure then use the appropriate formula.
For instance, when you’re dealing with a square you will use: L×L. In the case of a circle, you’ll use: π×radius×radius.
Cylinder Blind End Area (in square inches):
You’ll use the formula: PI×(Cylinder radiu)2
Again here, the formula will depend on the geometrical shape in question.
Cylinder Blind End Output (GPM):
The formula is: Blind end area÷Rod End Ares×GPM In
Cylinder Output Force (in pounds):
Use the formula: Pressure (in PSI)×CylinderArea
Cylinder Speed (in inches per second):
The formula is: (231×GPM)÷(60×Net Cylinder Area)
GPM of Flow Needed for Cylinder Speed:
Use the following formula: Cylinder area×stroke length in inches ÷231×60÷time in seconds for one stroke
Fluid Pressure in PSI Required to Lift Load (in PSI):
You’ll use the formula: Pounds of force needed ÷cylinder area

3. Hydraulic Motor Calculations

Consider the following key equations:
GPM of Flow Needed for Fluid Motor Speed:
Adopt the following formula: Motor displacement ×Motor RPM÷231
Fluid Motor Speed from GPM Input:
Use this formula: 231×GPM÷Fluid motor displacement
Fluid Motor Torque from Pressure and Displacement:
You’ll use this formula: PSI×Motor Displacement ÷(2×π)
Fluid Motor Torque from GPM, PSI and RPM:
You will use the formula: GPM×PSI×36.77÷RPM
Fluid Motor Torque from Horsepower and RPM:
Use this formula: Horsepower×63025÷RPM

4. Fluid and Piping Calculations

To calculate: Velocity of Fluid through Piping
Use the following formula: 0.3208×GPM÷Internal area
NOTE: For a more practical application of these formulas, you can download Target Hydraulics’ Hydraulic Calculations PDF.
Of Course, you’ll have to consider various hydraulic pipe designs and size, alongside other components such as manifolds and valves. There is the recommended pressures for each pipe.
Again, this calculations may involve some unit conversions. They are all indicated in the hydraulic calculations pdf.
Apart from these, you can visit the e4 Training. They offer a wide range of hydraulic system design calculators, simulations and courses.
With all these in mind, you can go ahead to design your hydraulic power pack circuit. This should be based on accurate calculations and selection of the right hydraulic power pack component.

For the 3D drawing designs, you’ll need Solidworks and Inventor. Remember this is where the design process begins.
Now, let us explore other components of hydraulic power pack designs.

Like any other design process, you have to specify each component at this stage.
I will focus on four unit diagrams here:

Hydraulic Manifolds

From chapter three, I am sure you understand the importance and function of manifolds in hydraulic power packs.

Remember, there are different types of hydraulic manifolds. This depends on the specific application of the hydraulic power pack.
Here are complete diagrams of the various types of hydraulic manifolds.

Oil Tank

Below is a picture of a hydraulic steel tank.

Electric Motor

It is the electric motor that drives the hydraulic pump. You can refer to chapter three for more information about motors.

Here is a bi-directional mini hydraulic power unit (HPU) assembling schematic:

Again, when it comes to the design process, we usually use symbols to represent the actual hydraulic components. These are universally acceptable hydraulic drawing symbols.
You’ll learn more about these in section 4.3.

Below are universally acceptable basic hydraulic symbols. Every hydraulic component in chapter 3 has a unique symbol representation.
For example, in hydraulic circuits, motors should be represented as shown below:

Apart from this, you can watch this video to learn more about schematic representation of control valves:

You can also access these resources: hydraulic symbols pdf, ISO Symbols for Hydraulic Systems and Basic Schematic Symbols Chart.
These circuit representations are crucial in any hydraulic power pack circuit design.
As a matter of fact, hydraulic power units (HPU) play an integral role in most systems. However, they have their unique advantages and disadvantages.
You will learn about these in chapter 5.
From the first four chapters, I am sure you’ve noticed that hydraulic systems are a perfect choice for a wide range of applications. This is due to the wide range of desirable features and benefits they offer as opposed to other equipment of the same category.
However, this does not imply that hydraulic systems are 100% perfect. They have certain advantages and disadvantages, which I will discuss in chapter five.

The advantages of hydraulic power units include:
Hydraulic power packs have high horsepower to weight ratio
When you compare hydraulic, mechanical and electrical system with the same power output, say 5hp, you’ll find that the hydraulic system is small and lightweight. In fact, you can hold it in the palm of your hand.
They are powerful compared to other lifting mechanisms
Hydraulic systems can create a huge amount of lifting force by applying or using just a small amount of force. For instance, a micro or mini power unit, with its lightweight, can create a high lifting power than either electric or diesel motors.

They can multiply forces to hundreds of tons, depending on the size of the cylinder and pistons. You don’t have to use complex gear or lever systems.

Convenient to use and install

Their small sizes make them easy to carry besides, you can install these power units in vertical or horizontal positions. They are also portable and you can mount them with a clear layout.
Hydraulic power packs have fewer moving parts, unlike most mechanical and electrical parts that use gear systems. This alone makes the system easy and simple to install.

You can easily adjust them to various speeds and lifting applications

This makes power units a perfect choice for a wide range of speeds and weight lifting capacities in industrial processes.

The torque and force can be held constant

Regardless of any changes in the system’s speed, a hydraulic unit can maintain a constant force and torque throughout the operation. As a matter of fact, you can hold either torque or force constant in any fluid transmission system.
Furthermore, you can also achieve a high torque even when the rotational speed is low. This is not always the case for electric motors.

Hydraulic systems are stable and rapid

Hydraulic power packs require a short period of time to lift a heavy weight to the required height or to exert the required amount of compressive force.

They are safe and easy to control

Hydraulic systems come with overload protection valves. The remote control mechanism makes it simple and easy to control the operation of a hydraulic power unit.
You’ll find that most hydraulic units have multi-functional control system and the motion can be reversed easily.
They are also considered to be safe, especially during an emergency stop conditions. Even in the hazardous environments, hydraulic systems can tolerate high temperatures, thus, there will be no instances of overheating.
Also, hydraulic systems are spark-free thereby eliminating the possibility of fire outbreak.

Hydraulic units are compact units

All the basic components such as electric motors, machinery, oil, pistons, cylinders, etc. come in a compact unit, hence easy to operate, transport, install and store.
You can easily realize a rectilinear motion with power packs
This is mainly due to the movement of the hydraulic piston within the cylinder. In fact, the hydraulic piston extend and retract linearly.
They are easy to design and cost effective to run after installation
All these reduces the cost of owning a hydraulic system and subsequent maintenance costs.
There’s a minimal loss of power over long distances
Hydraulic power packs can transmit hydraulic energy over long distance or through complex machines with small loss in power.

Even though hydraulic power packs are popular in a number of industrial and domestic applications, the systems have the following disadvantages:

Handling hydraulic oil can be messy

Power packs depend on hydraulic oil to generate a working force. In most cases, handling the hydraulic oil if you’re not a professional can be messy.
Moreover, at times it can be difficult to completely eliminate the leakage.
Apart from this, a hydraulic fluid may also catch fire in case of leakages. So, avoid hydraulic fluids that tend to be flammable.

They are sensitive to extreme temperature

Very high temperatures may affect the stability of a hydraulic power pack. For example, heat can destroy the hydraulic seals, causing significant pressure drop.
On the other hand, very cold temperature will result in a slow response of the hydraulic system since the hydraulic fluid will tend to thicken.

Hydraulic actuators have a low operating efficiency

Their system efficiency may range between 40 to 55%. The electric actuators have a system efficiency that ranges between 75 and 80%.
Moreover, using a throttle to change speed, especially over long distances may cause low transmission efficiency.
Again, as long as the hydraulic system is on, the power pack must keep the hydraulic system pressurized. This alone causes inefficiency since it uses power.

High maintenance and initial installation costs

For complex systems, initial cost is likely to be high. A good example is the standard hydraulic power packs.
Also, troubleshooting complex hydraulic systems can be a cumbersome process. They require constant inspection to fix all sealing problems that may cause oil pollution.
Remember, a leaking power pack may cause damage to the skin due to fluid pressure
It is quite evident that the hydraulic power units have a number of advantages compared to the disadvantages. This does not imply that they are the best equipment.
You need to examine the task at hand to choose the most appropriate power pack. This will help you to choose the right equipment that is reliable and can operate optimally.
Troubleshooting a hydraulic system can be a cumbersome process. However, with comprehensive troubleshooting guide, this should be a simple problem you can handle.
In chapter six, I will focus on how you can troubleshoot and repair simple problems in the hydraulic power pack systems.

Let’s look at each of these problems and their solutions in this hydraulic troubleshooting list:

The Motor is Not Running

In case of such a scenario, you need to inspect the following key parts:

• The electric motor

In the case of a DC power supply, there is always a possibility of low voltage. However, for the case of AC, there is always a high possibility that the power grid do not match the AC motor specifications.

• The motor

You need to check if the motor is in good working condition. That is, check all the terminals to ensure they are connected appropriately and rust free.

• Cable remote

The cable could be loose from the starter relay or broken, thus there could no continuity.

• Wireless remote

At times, the receiver may be loose from the starter relay. You should inspect the battery of the remote control to ensure they are in good condition.
The problem could be also be due to poor grounding. So, you have to inspect all electrical connections.

The Motor is Running But in a Wrong Direction

You should check the following:

• The electric motor

For DC motors, it could be + – inversely connected, so consider reversing the connections.

• Cable remote

The button may have been wired incorrectly.

• Wireless remote

The receiver may have been wired incorrectly
So, in both cases, you may consider reversing the terminals.

The Motor has Not Been Developing Proper Oil Rate

There are always two possibilities:

• The electric motor

Maybe the motor speed is not enough to create the required torque. So, so consider adjusting the motor speed.
Alternatively, there could be low voltage therefore, you need to check your power source.

• The hydraulic pump

The pump may not be suitable for hydraulic systems or it could faulty. So, you may consider replacing the pump.

The Pump Pressure is too Low

In such situations, you may consider the following:

• The electric motor

The power to the motor could too low to create the required torque to turn the pump. That is, either the DC voltage may be too low or for AC motors, the power grid may not match the

specifications of the motor.

Apart from these, rust and low motor speed may hinder the electric motor from developing the required torque.

• The hydraulic pump

Your hydraulic pump could be defective or it may be unsuitable for the application. So, you may consider replacing it.
Also, there could be a possibility of internal leakage. This is mainly brought about by wear and tear.

• The manifold and valves

Relief valve of the hydraulic system could be defective or there could be a possibility of manifold internal leakage.

• Filters

Your filters could be blocked thus preventing the sufficient amount of hydraulic from flowing into the system.

• The hydraulic fluid

The viscosity of the fluidcould be too, and this is mainly due to very low temperatures.
Apart from all these, cylinder leakage may also cause low pump pressure.

specifications of the motor.

You should consider the following:

• About the hydraulic pump

This problem could be due a defective pump or unsuitable pump type. At times this could also be due to internal leakages brought about by wear and tear.

• Manifold & valves

There could be a manifold internal leakage.

• Filter

The filter could be blocked.

• Connectors

This problem could be due to couplings wrongly aligned or leakages in the suction pipe. At times, it may also be due to defective or loose coupling mechanism.

• Oil tank

The oil level could be too low or oil is not enough.
Apart from these the pump may not be developing oil when the hydraulic power unit is wrongly mounted.

The Cylinder Runs On

This problem could be due to the following:

• The electric motor

It is common when the starter relay is bad. You may consider replacing it.

• Cable remote

The main causes include button wrongly wired from the inside, a cable is loose from the starter relay or the switching is too fast. Also, when the cable is loose from the solenoid coil the cylinder may run on.

• Wireless remote

This happens when the receiver is wrongly wired, switching is too fast or the receiver is loose from the starter.

• Manifold and valve

It occurs whenever there is internal leakages, faulty bleeding, the solenoid valve is defective, relief valve has malfunctioned or the valve is dirty.
At times, this could be due to the cylinder inlet seal leakage of cylinder rod that is worn out.

When the Cylinder Cannot Extend

The problem could be due to the following:

• Electric motor

For DC motors, the battery could be too low while in the case of AC motors, the power grid may not match the AC motor specifications. Also, it may be due to low motor power or thermal pressure lock.

• Cable remote

The cable could be loose from starter relay, there could be a thermal pressure lock or fast witching.

• Wireless remote

It could be due to fast switching or the receiver may be loose from the starter relay.

• Hydraulic pump

The pump could be defective or unsuitable pump type. At times, the problem could be due to internal leakages brought by wear and tear.

• Manifold & valve

It could be due to manifold internal leakage, directional valve not shifting properly or solenoid valve may not have sufficient energy.

• Filter

The filter may be blocked.

• Connectors

This could be due to the coupling wrongly aligned, loose coupling, defective coupling or leakage at the suction pipe.

• Oil tank

There could be low oil level in the tank (oil not enough).
Apart from these, the problem could be due to cylinder leakage, packing on cylinder rod worn out or hydraulic power unit could be wrongly mounted.

The Cylinder Cannot Hold Load

This problem could be due to:

• Manifold & valve

There could be internal leakage or both the check valve and solenoid valves may be defective.
The problem may also be as a result of cylinder inlet seal leakage or the rod getting worn out.

The Cylinder Drops Too Slow or Cannot Drop

This is due to:

• Electric motor

For DC motors, the battery voltage could be too low while for the case of AC motors, the power grid may not match the AC motor specifications.
At times, the power of the motor may be too low or there could be thermal pressure lock.

• Cable remote

The cables could be loose from the solenoid, there could be thermal pressure or the system switching too fast.

• Wireless remote

Its receiver may be loose from the solenoid or the switching may be too fast.

• Manifold & valve

The manifold, oil return line may be clogged from the orifice, throttle too tight, loose inlet or solenoid valve not energized.

• Oil tank

It could be too full.

The Cylinder Drops Not Stable

The problem could be due to:

• Electric motor

For DC motors, the battery electric quantity may not be enough, while for AC motors, there could be instability in the power grid. Also, the motor may have rust.

• Cable remote

The cable could be loose from the solenoid coil or it may be switching too fast.

• Wireless remote

Its receiver may be loose from the solenoid coil or the switching could be too fast.

• Hydraulic pump

This could be due to internal leakage as a result of wear, defective pump or unsuitable pump type.

• Manifold & valve

There could be manifold oil return line leakage, throttle too loose or solenoid valve not energized properly.

• Connectors

The connectors may be wrongly aligned, loose or defective. A possibility of suction pipe leakage is also high.
At times, the problem may be due to cylinder outline seal leakage or a worn out cylinder rod.

The Start Solenoid Just Click and the Motor is Not Engaging

This is a result of:

• Electric motor

The DC battery electric quantity insufficient or the AC power grid does not match that of the motor. Rust may also be a contributing factor.

• Cable remote

A cable may be loose from starter relay, there could be a thermal pressure lock or the systems could be switching too fast.

• Wireless remote

The receiver could be loose from the starter or the switching too fast.
Noise:
The noise is due to:

• Electric motor

The DC voltage may be too low or the AC power grid may not match that of the AC motor specifications. Rust is also another cause of noise.

• Hydraulic pump

There could be internal leakage due to wear, unsuitable or defective pump type.

• Manifold & valve

This could be due to internal leakages, faulty bleeding, dirty valve or defective solenoid that may cause leakage in valves.

• Connectors

The coupling may be wrongly aligned, loose or defective. Leakages at the suction pipe may also cause noise.

• Oil tank

Oil level may be too low.

• Hydraulic fluid

The viscosity may be too high due to extremely low temperature
Apart from these, there could be a cylinder leakage or a worn out cylinder rod.

An Excess Operating Temperature

The high temperature is due to:

• Electric motor

DC voltage may be too low while the AC power grid may not match the specifications of the AC motor. Rust may cause overheating.

• Hydraulic pump

The hydraulic pump may be defective or unsuitable.

• Manifold & valve

The valves may be dirty or worn out.

• Filter

The filter may be dirty

• Connectors

The connectors may be wrongly aligned, loose or defective.

An Excess Operating Temperature

This is due to:

• Hydraulic fluid

There could be leakages in suction or return lines.

• Oil tank

The fluid level may be too low

• Hydraulic fluid

It could be unstable hydraulic fluid.
Clearly, a hydraulic power pack may have simple, but difficult to identify problems that can compromise its functionality. With all these, I am sure you can identify the exact problem that may reduce the efficiency of the hydraulic power pack.
In the next chapter, you’ll learn how to manufacture a hydraulic power. This will be a simple process since you had learned about the hydraulic power pack design process in chapter 4.

As a matter of fact, manufacturing say a hydraulic pump or an electric motor alone can be another eBook. Here, I’ll focus on assembling different components that make a complete hydraulic power pack.

In this section, you’ll learn about the following key aspects:

• How to build hydraulic power pack
• How to build a homemade hydraulic power pack
• How to calculate hydraulic power

Let’s start with:

This is basically the process of assembling a hydraulic power pack. It is a simple procedure that involves putting all parts you had selected in chapter 4 together to form a complete machine.
Let’s see how you can go about the entire process:

Identify All Essential Components of the Hydraulic Power Pack Unit

As I had mentioned earlier, a hydraulic power pack has several components that you’ll assemble together. So, before, you begin the process, ensure you have all the components and equipment you’ll need for the process.
Here is what you need:

• A voltage source; in this case you’ll require a DC12V and DC24V
• Remote control; this can be cable or a wireless remote control
• Electrical diagram; you need an electrical diagram design of the power unit.
• Hydraulic circuit; this is the hydraulic power pack circuit diagram
• Hydraulic design; it’s the electric power unit design
• Power pack drawing; it is basically how to wire hydraulic power pack
• Electric cables

With all these in place, you can begin the assembly process:

Wire a DC Motor for a Single Acting Hydraulic Power Pack

You’ll connect the motor to the voltage supply. Always ensure you’ve chosen the right terminal and that the power source can supply sufficient amount of voltage.
It’s the motor that rotates the hydraulic pump, which pushes the hydraulic fluid in the circuit.
Again, you’ll realize that wiring a single acting hydraulic system may vary slightly from the double acting hydraulic power pack. However, the working principle remains the same as indicated in the previous chapters.

Wire DC500W/800W Motor Single Acting Hydraulic Power Pack

It’s now time to couple electric motor to the hydraulic pump. Here is how the wiring diagrams should look like:

Wire DC Motor Double Acting Hydraulic Power Pack

In case you intend to use a double acting hydraulic system, here is how your diagram should look like:

Wire a Double Cartridge Solenoid Valve Drawing

The circuit diagram below resembles that of a dump trailer. Here is how to go about it:

Wiring a Double Acting Hydraulic Power Units

For a double acting hydraulic power unit, here is how the wiring should look like:

Wire DC Wireless Remote and Quick Connector

Here is how you can wire a DC wireless remote for your single acting hydraulic power pack:

As you can see, wiring a hydraulic power pack is a simple process. In each circuit, you should use the colors to identify the right cable for a specific port/ connection.
When you interchange these cables, the motor may run in the opposite direction or the hydraulic power pack may not work completely.
Again in case your hydraulic power pack fails to work after wiring, you can refer to chapter 6 – how to troubleshoot a hydraulic power pack.
Generally, during the assembly process, you’re simply trying to put different components of the hydraulic power pack together. You can see how this system looks like when it has been fully disassembled:

These parts are: 1-DC motor cover; 2-DC motor; 3-Shaft joint; 4-Relief Valve; 5-Flow control valve; 6-Central Manifold; 7-Hydraulic Gear Pump; 8-Return oil pipe; 9-Suction pipe; 10-Hydraulic oil tank; 11-Air breather; 12-suction filter; 13-two position two way normally closed solenoid valve; 14-Check Valve; 15-Mounting Bracket &16-Remote control pendant.
Of course, after you’ve successfully assembled the device, you should have a component that looks like this:

Apart from these, in the recent past, a number of people have been trying to make their homemade hydraulic power packs. You’ll learn about this in section 7.2.

For people who cannot afford to buy a brand new hydraulic power pack or enjoy doing DIY projects, this could be a better option.
Let me start by introducing you to a homemade hydraulic power pack video courtesy of Smalls4068.

In the video, you’ll learn how to make your hydraulic power pack at home. It contains all the essential aspects you need to consider throughout the assembly process.
Even when you opt for a homemade unit, the best way to go about the process is to purchase a fully tested hydraulic power pack kit.
Remember, quality testing, as you’ll learn later in chapter 8, ensures that every component of the hydraulic system operates optimally an efficiently.
Here are some of the key factors you need to consider for a hydraulic power pack kit:

Homemade Power Pack Unit Specifications

There are very many units with different system specifications. You need to consider the following:

• Types of hydraulic pump
• Electric motor specifications
• Maximum operating pressure
• Size of the oil tank or reservoir
• Suction filters
• Valves
• Pressure gauge

You can refer to chapter 3 to learn more about hydraulic power unit components.
Remember, assembling your own hydraulic power pack at home will save you a lot of money.
Although most of these units are small, you can use them in a wide range of applications such as in shop presses, punch presses, sheet metal rollers, metal brakes, etc.
Still, you need to buy the kits from reputable suppliers.
The essence of having a power pack is to ensure that you have enough hydraulic energy that can do some work.
So, even if you assemble your own power pack, or purchase one that is already assembled by the manufacturer, it is important to determine the amount of hydraulic energy it can develop.
You can only do this by evaluating every component to assess its contribution to the overall efficiency of the system. Let’s learn how to calculate the hydraulic power.

In chapter 4 of this eBook, during the design process, I did share a number of formulas you need to analyze a hydraulic power pack.
Well, when it comes to the calculating the hydraulic power, the situation is not different. In fact, you’ll need quite a number of those formulas.
That actually forms a fundamental part of the calculation processes. In fact, the online scripts are developed from these equations and formulas.
In this section, I will focus on the automated methods/online scripts.

7.3.1: How to Calculate Hydraulic Power

There are a number of online hydraulic power calculators you can use to analyze the performance of the hydraulic systems.
Basically, these are scripts where all you need is to enter specific values indicated in the dialog box, follow some instructions and it will display the exact hydraulic power.
Below is an example of a script you can use to determine a pump power:

Even with these scripts, there are certain values that you’ll need to know depending on system parameters:

• To calculate power in N( kW)

You need to know the pump flow rate in liters/minute, pump efficiency and pressure.

• To calculate pressure due to the electric motor and hydraulic pump

You’ll need to find pump flow in liters/minute, pump efficiency and power

• To calculate the hydraulic pump flow rate

You’ll need to know power, pump efficiency and pressure.
On these online scripts, you don’t have to go through the tiresome process of substituting these values in the hydraulic equations and formulas.
However, their accuracy will depend on the person or company that developed the script. If it’s from a trusted hydraulic equipment manufacturing company or education website the better.
A good example is The Engineering ToolBox. It has a wide range of online calculators.
In the last seven chapters of this hydraulic power pack eBook, the focus was mainly on having a clear understanding of what these pumps are all about.
Still, a hydraulic power pack cannot be used for any application until its quality is verified and certified. But, how can we achieve this?
You’ll learn everything about quality testing and verification in the next chapter.

Hydraulic power pack quality control is a rigorous process considering that this hydraulic system has a wide range of components.

To ensure a hydraulic power pack operates efficiently, you need to conduct the following tests:

8.1.1: Testing Quality of Hydraulic Fluids

You can assess the quality of hydraulic fluids using different processes. Some of the most common analysis methods include:

• Particle distribution
• Gravimetric
• Water content
• Proton induced X-ray
• Ferrographic wear debris

Normally, you’ll find that presence of some particles of other substances in the hydraulic system may degrade the hydraulic fluid. Others may lead to acid formation, hence, undermining the performance of the hydraulic fluid.

Below is a video showing hydraulic oil analysis, courtesy of Donaldson Company:

https://www.youtube.com/watch?v=JfOlfmyn2XM
Remember, all these tests must conform to the ASTM standards for hydraulic fluids and oils.

8.1.2: Testing Quality of Hydraulic Pumps

To supply the hydraulic fluid to the circuit, you need a high quality pump. Therefore, you need to inspect the pump regularly to ensure it delivers its rated flow, operates under normal hydraulic system pressure and temperature.

This makes a system relief valve an important accessory. You can easily tell whether the pump is supplying is rated flow through a relief valve.

You may use a flow meter to evaluate the pump. This doesn’t cost a lot of money.

In this process, there are two scenarios you need to consider:

• You can increase the pressure to the normal system pressure. If there is no a significant drop in fluid flow, then your pump is good.
• For a faulty or a bad pump, increasing pressure on the relief valve will result in significant drop in the flow rate.

Other methods of testing whether your hydraulic pumps are working efficiently may include:

• Test 1

Palace you hand or use a thermometer to measure the temperature outside the pump. An increase in temperature will imply there hydraulic oil is leaking, causing friction, which manifests itself as an increase in temperature.

For accurate analysis of the problem, you can use other sophisticated equipment such as the ultrasonic heat gun. This will help you to identify the exact location where there is a problem.

• Test 2

You can perform a flow meter test on the pump during no-load and under load conditions.

Apart from these, there a number of hydraulic pump testing equipment in the market you may also consider.

Use these machines to check whether your pump is operating optimally under normal working conditions.

8.1.3: Electric Motor Quality Testing

The efficiency of a hydraulic system starts by analyzing an electric motor. There is a wide range of accessories you can use to test an electric motor either in its static or dynamic state.

Such instruments can deliver a comprehensive test results about the condition of the motor. A good example of the motor testing equipment is the SKF machines.

Obviously, a high quality motor should run at the rated speed, consume rated power, deliver rated torque and easy to control.

During the manufacturing process of electric motors, you should be able to detect weaknesses and faults in the insulation and monitor the condition of the motor as it operates.

8.1.4: Hydraulic Cylinder Quality Testing

It is in this section that the hydraulic power is converted into mechanical energy. Therefore, the cylinder should be tested and this should be based on both design and functionality.

The quality testing process should include analyzing dimensions of the cylinder, layer thickness, pressure and leakages.

You need to conduct these tests whether the cylinder is in vertical or horizontal position.

In the case of hydraulic power packs, you need to test the cylinder when it is already fixed in the system.

Like in the case of the electric motors, you should test the hydraulic cylinders both in the static and dynamic mode.

8.1.5: Hydraulic Valves and Manifold Quality Testing

In hydraulic systems, you need test hydraulic manifolds, solenoid valves directional valves and cartridge. The flow in these components is tested using high quality and standardized equipment.

All these procedures aim to ensure the whole hydraulic system operates optimally.

Generally, the hydraulic system testing and quality verification may involve:

• Pressure and flow control
• Cartridge, loader, directional, relief and auxiliary valves
• Transmission control

Each process will require a unique equipment whose quality should be determined by the testing laboratory.

To install hydraulic power packs, you need appropriate tools and equipment that will ensure you do the work efficiently and accurately.

In this section, I will introduce you to some of these tools and equipment. Of course, these should be alongside the testing equipment in section 8.1.

Let’s review some of these tools:

8.2.1: Electrical Measuring Equipment/Instrument

You’ll use this device to confirm the voltage and current match that of the specification of your
motor. Remember, the motor rating should be the same as your electricity supplier or generator.

Furthermore, an instrument like a multimeter, to measure current, resistance, voltage and continuity in the circuit.

8.2.2: Temperature Measuring Equipment

A thermometer will help you to determine the working temperature the hydraulic system. For instance, you need to check the oil temperature of the oil reservoir regularly.

Moreover, you’ll use the thermometer to test the temperature of the hydraulic pump. With this, you can tell whether there is wear and tear in your hydraulic pump that may cause friction.

8.2.3: Tightening/Fastening Material

You need to tighten various sections of the hydraulic power pack to make it a complete circuit. This includes tightening and fastening screws and shafts.

Generally, a hydraulic power pack comes with simple tools and accessories. They are simple to use so you don’t need any sophisticated training.

Again, as you use these tools to install or assemble hydraulic power packs, there are certain precautions you need to note.

Whenever you are planning to install a hydraulic power pack, you need to observe the following:

• Clean/flush the old system

This will prevent the possibility of blocking the hydraulic system. Good example is the single acting tipper systems or scissor lifts.

Operating a dirty system may return dirt particle into the hydraulic power pack thus, clogging the filters.

• All electrical components should be isolated

By isolating these systems, you’ll avoid possibility of electric shock. You need to be cautious when dealing with systems that should automatically start the power pack.

• Never adjust the system valves beyond the specifications of the manufacturer

This should include connecting electrical components, manifolds and valves. More importantly, you need to keep the safety or relief valves within the recommended range.

• Do not overfill the hydraulic power pack reservoir

This is common, especially when you’re dealing with a micro hydraulic power pack or a mini hydraulic power pack.

Their tanks are basically small. So, you should only refill it after all the air has been bled from the hydraulic system.

With all these in mind, you should go about the assembly process successfully. Always remember to refer to manufacturers guidelines during this process.

Apparently, there are many types of hydraulic power packs in the market with varying capacities and features. This explains the variation in prices.

Let’s review the hydraulic power pack price.

Whenever you’re shopping for a new hydraulic power pack, it is important to consider the
following key aspects:

• Size of the hydraulic power pack

Large power packs are more expensive compared to the small types. For instance, a standard hydraulic power pack is more expensive than micro or a mini hydraulic power pack.

This classification (size or capacity) is based on comparing the following key aspects:

1. Hydraulic pump and electric motor rating.
2. Size of the hydraulic cylinder
3. Amount of power consumption
4. Working pressure
5. Capacity of the power pack, etc.

Basically, you should refer to the power pack specification/product manual.

• Consider the type of technology

A power pack with a sophisticated technology or complex manifold is likely to be more expensive. One such example is the custom made hydraulic power packs.

The customized hydraulic power packs are more expensive compared to the standard designs. This is because the hydraulic power pack manufacturer may decide to incorporate a technology that is only unique to a specific model.

It is always based on the specific requirements of a customer. That is, including other accessories such as a wireless remote control is more likely to increase the price of a power unit.

• Brand of hydraulic power pack

Different hydraulic power unit brands have their unique price tag. For example, Target Hydraulics power pack is relatively cheaper compared to most of its competitors.

Again, you’ll find most reputable brands to be more expensive.

In short, these are some of the main factors that determine the price of a hydraulic power pack.

So, let’s have a review of the hydraulic power pack cost.