What is hydraulic power pack components ?
What Is a Hydraulic Power Pack?
What are the applications for hydraulic power packs?
Mobile hydraulics applications have recently been increasing so much with hydraulic power packs. Some applications are as follows; dump trailers, electric sanitation trucks, snowplows, telescopic logistics equipment, like the dock leveler, car tailgates, wing trucks, electric pushcarts, and electric pallet lifts. Other uses include car lifts, scissor lifts, electric operating tables, and special equipment on elevators. Compact hydraulic power units (HPU) work well at high pressure, with its low flow hydraulic system, small size, simple elements, and affordable price.
How many different types of hydraulic power units are there?
These units include; single-acting hydraulic power units, double-acting hydraulic power units, power units, and other complex special effects work.
In the motor voltage are DC hydraulic power units, and AC hydraulic power units. In the tank installation are vertical or horizontally mounted hydraulic power units.
The valves are controlled by manual operation hydraulic power units, and electric control hydraulic power units.
Here is a DC Hydraulic Power Unit drawing to show you what the main Hydraulic power packs components 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
What components do hydraulic power units components include?
(HPU) Hydraulic power units are a hydraulic system with hydraulic actuators (hydraulic cylinders, hydraulic motors) connected to the control valve operation to achieve the operation of the equipment for the adopted oil pressure apparatus. Hydraulic power units come complete with a power section (electric motor, hydraulic pump), the control section (pressure valves, directional control valves, flow control valves), and the auxiliary section (couplings, manifold block, suction pipe, return pipe, tank, air breather, etc.).
First, the Power Section
1) Motor – hydraulic power unit power source
The motor hydraulic power unit’s main role is to convert electrical energy into mechanical energy. Generating a driving torque, hydraulic power units function as a power source. Hydraulic power units are commonly classified according to the power supply of the motor, and can be divided into DC motors and AC motors. Where in the AC motor and the DC motor include 2 poles and 4 poles.
Electric motor common parameters
- Rated power is the motor’s maximum working power recommended operating conditions. POWER RATING is motor power.
- Rated voltage or operating voltage. Since the motor can generally operate at different voltages, the voltage is directly related to the speed, and other parameters have to change accordingly, so that the voltage is only a suggestion.
- No-load speed. The unit is RPM, meaning revolutions per minute. Since there is no load speed reverse torque, the output power and the stall situation is different, the effect parameters only provide maximum speed of the motor at a predetermined voltage.
- Stall torque is an important parameter to take a lot of the load of the motor. That is, when the motor is reversed by an external force to stop the rotation torque. If the motor stall phenomenon occurs often, it will damage the motor, or burned driver chips, so when you choose the motor, which, in addition to speed, is the first parameter to be considered. Usually the relationship values and the operating voltage is not very close. Note that, however, stalled over time, the motor temperature rises rapidly, the motor’s value will decline rapidly.
- No-load current is closely related to current and torque. There is certainly no-load current, because voltage and energy formed is divided into potential energy and heat energy consumption. Heat is related to the motor coil, the better the motor, at no load, the smaller the value.
- Starting current. This parameter is also important. For a good motor, under the same acceleration, the starting current will be small.
2) Hydraulic pump – the heart of the hydraulic power unit
Hydraulic pump means a hydraulic power unit capable of converting mechanical energy into hydraulic pressure. Driven by the motor, providing flow and pressure of the hydraulic actuator action desired. Thus, it can be said that the hydraulic pump is the “heart.” There are several types of hydraulic pumps: gear pumps, vane pumps, and piston pumps.
Compact hydraulic power units normally work with hydraulic gear pumps. At present, the industry’s leading manufacturer in Italy is Marzocchi pumps High Pressure Gear Pump Company. Gear pump advantages are: simple structure, easy fabrication, low cost, small size, light weight, self-priming performance, not sensitive to pollution of the oil, reliable, and high speed range.
How Hydraulic gear pump work
As shown capstan clockwise, then seal the suction chamber at T, because the tooth is disengaged children volume increases, the formation of a vacuum, atmospheric pressure hydraulic oil tank into the suction chamber T, the room filled with alveolar, this is the pump suction process; with the rotation of the gear, with oil constantly being brought into pressure oil chamber P, teeth into engagement on that side, the volume decreases, forcing oil output, this is the process of pumping oil. And syringe injection medicine procedure is very similar.Gear pumps common parameters
- Pressure rating refers to the maximum under the premise volumetric efficiency of the pump, and the life of the rated speed, continuous operation of the pump allows the use of pressure to ensure that more than this value is overloaded. Rated pressure and maximum working pressure of the pump pressure is not actually at work.
- Displacement refers to the pump shaft rotation, excluded volume of oil. Here we must distinguish between displacement and rated flow. Rated flow at rated pressure and speed conditions, the output of a predetermined flow rate. Speed-dependent, but no relationship between displacement and speed.
- Efficiency, broken down into mechanical efficiency and volumetric efficiency, showed losses in torque and pump flow.
Second, the control section As with the development of the hydraulic power unit cartridge valve in the increased range, a wide range of hydraulic power units are also increasing. The main production base for the current international cartridge valves in the United States include Hydraforce Hydraulics Cartridge Valves, Sun Hydraulics, Eaton vickers (Eaton), Parker Hannifin (Parker), and Fluid Control. Sterling Hydraulics and Integrated Hydraulics are companies in the UK. In Germany there are Bosch-Rexroth, HYDAC, and Fluid TeamWandfluh, and Bucher-Frutigen are from Switzerland. In Italy there are Comatrol and Oil-Control. In Sweden, and Denmark Sauer-Danfoss. Keta Hydraulics and Haihong Hydraulics are from China. And Target Hydraulics company from Ningbo Hydraulics.
1) Pressure control valves Pressure control valves on the hydraulic power units with pressure relief valve, sequence valve, relief valve, are pressure relay-based. Almost each hydraulic power unit comes complete with a relief valve. Sequence valves, relief valves, and pressure switches on some special hydraulic power units have a sequence of actions, and the same system has different working pressures used, such as dock leveler hydraulic power units for logistics equipment and paper cutter production line hydraulic power units.Relief Valve – umbrella of hydraulic power unit Pressure relief valves on the hydraulic power unit have primarily a security role, they limit the maximum pressure to avoid other hydraulic components, and pipe damage. As part of a back pressure relief valve in the hydraulic power unit, causing back pressure to increase the stability of motion.
1—Valve body 2—valve spool 3—valve body 4—spring seat 5—spring 6—adjusting lever 7—screw-in body 8—Locking nut
How a relief valve works Under normal operation ①chamber to chamber ② closed until the liquid pressure chamber ① sufficient to overcome the spring force of the valve body from the valve seat, ①chamber communicating with the chamber②, the flow of oil from the chamber ①cavity②.
2) Directional control valve Hydraulic power units have varied different types of directional control valve, check valves, P-O-check valves, shuttle valves, solenoid valves, hydraulic control valves, electric proportional valve, and so on.
- Check valve (one-way valve) oil traffic in one-way.
One-way valves, also known as check valves, allow fluid only in one direction through the reversing valve closing direction. The main role of the check valve in the hydraulic power unit is: to keep the system pressure constant for a period of time and other pressure retaining components, installation preventing normal operation of the hydraulic pump, and hydraulic shocks in pump outlet position, the check valve installed in the back part oil used as a back-pressure valve. According to the role of one-way valve in the hydraulic power unit, its performance was mainly: oil pressure loss circulation of small forward, reverse seal better performance, quick action, low noise.
1-Valve seat 2-Check valve spool 3-Spring 4-Screw Plug
How check valves work The pressure port① is higher than the pressure port② plus spring force, the spool is pushed, the channel is open, fluid forward through the check valve (① flow to ②).When the port ② pressure plus the spring force is higher than the port ① pressure spool is pressed against the spring force and fluid pressure on the valve seat, the flow is turned off.
- Directional valve – oil traffic red and green lights
Directional valve is the largest amount components of hydraulic power unit request. Directional valve use of different relative positions in hydraulic power pack. Hydraulic power unit requirements: the oil through a less pressure loss, less amounts of the oil leakage gap between the mouth commutation reliable, sensitive, reversing smoothly without impact. According manipulation way valve used in the hydraulic power unit valve can be divided into: manual valve, solenoid valve, and motorized valves For example, in the automotive lift hydraulic power unit, electric pallet truck hydraulic power unit, electric car pushing hydraulic power unit, hydraulic power units, and other tipper trailers on two two-way solenoid valve with the most.
Hydraforce SV type two-way solenoid valve works When the solenoid valve coil power, the two-way solenoid valve can do a one-way valve to allow flow from ① to ② chamber cavity, and the cavity reverse blocking oil from ② to ①.Solenoid valve coil is energized, the lifting force generated by the coil, valve open, fluid chamber from ② to ①, ② and ① chamber to the fluid chamber due to structural reasons strong resistance.
3) Flow control valve Flow control valve referred to the flow valve, is by changing the orifice flow area to achieve flow control. It is a control valve components to control the speed of movement of the element. Flow valve can be opened as a small mark of “taps.”Flow valves can generally be divided into: a throttle valve, 2-way flow control valve (also known as pressure-compensated flow valve), the three-way flow control valve. Currently on the hydraulic power units, Hydraforce is mainly used for NV Throttle and Comatrol’s SC13 type 2-way flow valve.
Hydraforce FR-type pressure compensated flow control valve works FR-type pressure compensated flow control valve ② from holding chamber effluent flow rate constant and is not affected by the load pressure changes in the circuit downstream of the chamber ②, when the flow through the valve in the control orifice pressure differential created more than 5.5bar, valve begins response to load changes within a pressure range of 7.6 ~ 240bar can maintain accurate flow, reverse flow (chamber ②to chamber①) through the control orifice, no pressure compensation, and orifice same. Third, the auxiliary section Hydraulic auxiliary components of the hydraulic power unit have a “supporting role”, but it is also an important part of the hydraulic power unit, Types of hydraulic auxiliary element is varied, including: tank, filter, suction pipe, return pipe, an intermediate manifold, control switches, pressure gauge, accumulator, and so on. The right choice and ensure the rational use of the hydraulic power unit is reliable, stable and has a very important auxiliary hydraulic components.
- Tank (Hydraulic Reservoir)- the hydraulic medium required for storage of the hydraulic system, as a heat sink, the role of the liquid medium in air separation and precipitation of impurities.
- Filter – filtration of impurities mixed in with the oil, foreign particles in a controlled hydraulic power unit normal operating range, the protection of hydraulic components.
- Central manifold – Installation Connecting the motor and gear pump, simplifying the piping, integrated control valve of the hydraulic power unit compact and convenient. Replace with a different intermediate manifold control valve can be achieved on different principles of hydraulic power unit, which makes the intermediate manifold high versatility.
Cartridge solenoid valves A cartridge directional solenoid valve will control which element the hydraulic fluid will flow to. There are many different types of directional control valves. Normally, valves are designed with coil and cartridge spools or poppets.The valve is generally specified by a number of positions and a number of ways (ports). The valve is made up of two parts, the body and the spool.
Two (2) Position, Two (2) way This valve has two positions (2 boxes) and 2 ways (ports); thus 2 position, 2 way. This valve is normally closed because both ports are blocked when in neutral.
Three (3) Position, Four (4) way This valve has three positions (3 boxes) and 4 ways (ports); thus 3 position, 4 way. It is shown with a closed center, when the valve is neutral all ports are blocked. The small boxes on each end with diagonal lines through them, C1 and C2, are electrical coils, this is an electrically actuated valve. The port marked P is Pressure and the port marked T drains to tank. The ports marked A and B connect to an external device, like a cylinder. When C1 is energized the valve will shift, putting pressure to the B port and draining the A port to the tank. Likewise when C2 is energized the pressure port connects to the A port and the B port drains to the tank.
Typical applications: hydraulic power packs, hydraulic cartridge valve manifold systems, mobile hydraulics, and etc.
Hydraulic flow valves
Cartridge flow control valves manage the flow by decreasing or increasing the opening at the throttling point. They are called throttle valves. The throttle check valve for speed control in one direction of flow.
This unit is a screw-in, cartridge type, bi-directional hydraulic flow valve. Normally we use it in T line of our hydraulic power unit to control cylinder speed.
Typical applications: hydraulic power units, hydraulic cartridge valve manifold systems, mobile hydraulics, and etc.
Hydraulic pressure valves
Hydraulic pressure valves include hydraulic pressure reducing valves and hydraulic relief valves. Hydraulic Relief Valve.All hydraulic systems must have a pressure relief valve in P line with the pump. The pressure relief will drain into the tank. Because hydraulic fluid oil is normally non compressible, if the fluid can’t go anywhere, the pump will stop or fail. And this may damage the pump and system components. The relief valve will control the maximum pressure in the hydraulic system to limit the system pressure below the safety pressure level.
Typical applications: hydraulic power packs, hydraulic cartridge valves, manifold systems, mobile hydraulics, etc.