Hydraulic pumps are the lifeblood of hydraulic systems, finding application in cranes, excavators, and other heavy machinery. Understanding the definition, principles of working, and hydraulic pump symbols not only aids in system design but also ensures that future maintenance and troubleshooting are simplified. Here in this article, we will guide you through these three aspects to familiarize you more with hydraulic pumps.
What is a hydraulic pump?
A hydraulic pump is the source of power for hydraulic systems, converting mechanical to hydraulic energy. It powers actuators of the system by creating fluid with certain pressure and flow rates.
How does a hydraulic pump work?
What is the working principle of a hydraulic pump? The principle is quite simple actually: it is a conversion of mechanical energy into hydraulic energy by means of the change in the volume of the working chamber. When the motor turns the pump, the chamber continuously repeats two processes—suction and compression. It gives the system a continuous fluid flow.
Oil Suction Phase
Ever wondered how hydraulic fluid enters the pump? As gears, vanes, or pistons move to expand the chamber space, internal pressure drops. At this point, hydraulic fluid from the reservoir is “pushed” in by atmospheric pressure.
Oil Displacement Phase
How is the oil then pushed out? Everything is reversed: As the chamber gradually reduces in size, the oil inside it is continuously compressed and forced out through the outlet into the hydraulic system.
So, a hydraulic pump operation is actually a continuous process: it takes in hydraulic oil and expels it simultaneously. You can compare it to the “heart” of the hydraulic system, with each revolution giving a continuous supply of energy.
Why is it important to understand hydraulic pump symbols?
In a system of hydraulics, depending only on words to describe pumps, valves, and piping can be inconvenient and inaccurate. Try to define with many words: “This is a variable displacement pump,” “This is a directional control valve”—would that be easy to understand?
It is precisely why engineers use standardized graphical notations for describing hydraulic components. With the use of these symbols, you can instantly identify from one schematic diagram what type of pump it is, in what direction it flows, how to connect it with other components, and how the system will work.
That is, symbols are hydraulic engineering’s own language that everybody can speak. Wherever you are engaged in designing or servicing hydraulic systems, you can understand other individuals’ hydraulic system drawings and designs since you can read these symbols.
What is the basic shape of a hydraulic pump symbol?
In hydraulic system diagrams, the symbol for a hydraulic pump is actually quite straightforward. By focusing on a few key elements, you can quickly identify it.
Circle
You’ll first notice a circle, representing the rotating component. Whenever you encounter a pump or motor, it will typically feature a circle as its main shape. Next time you review a diagram, start by looking for this “circle.”
Solid Triangle
The triangle indicates fluid flow direction. How to tell? Simple—pointing outward signifies a hydraulic pump (mechanical energy → hydraulic energy); pointing inward indicates a hydraulic motor (hydraulic energy → mechanical energy). See how intuitive that is?
Diagonal Arrow
Sometimes you’ll see a diagonal arrow crossing a circle. What does this mean? It tells you this is a variable displacement pump—its flow rate can be adjusted, not fixed.
Parallel Short Lines
If you spot two parallel short lines next to a circle, they usually represent the suction port and discharge port. In other words, this pump isn’t “integrated” with the tank; it needs external piping to connect.
Curved Arrow
Finally, you might notice a small curved arrow next to the circle. Don’t overlook it! This symbol indicates the pump’s rotation direction. A single arrow means it rotates in one direction only; a double-headed arrow signifies bidirectional operation.
What are the symbols for hydraulic pumps?
If you are familiar with the diagrams of hydraulic pumps, then you’ll master their symbols in no time. The following are some standard hydraulic pump symbols used in design drawings.
Hydraulic Pump Symbols
Hydraulic pumps are hydraulic system moving components used to control flow rate. Their symbols are usually classified based on flow rate, flow direction, and rotation direction. The main categories are: single-direction fixed-displacement hydraulic pumps, double-direction fixed-displacement hydraulic pumps, single-direction variable-displacement hydraulic pumps, and double-direction variable-displacement hydraulic pumps.
Single-Direction Fixed-Displacement Hydraulic Pump
The single-direction fixed-displacement hydraulic pump is the most basic type. It delivers a constant flow rate per unit time in only one direction, which remains unaffected by system pressure changes. You’ll see a solid triangle on diagrams, serving as a constant flow source in the system for supplying steady hydraulic operation.
Bidirectional Fixed-Displacement Hydraulic Pump
Unlike the fixed-displacement unidirectional pump, this pump provides fluid in both directions. Schematics have two solid triangles, showing their capability to give reciprocating motion in hydraulic cylinders or motors. This pump is a good choice if your application requires bidirectional motion.
Unidirectional Variable Hydraulic Pump
The flow rate of unidirectional variable hydraulic pump varies with system pressure or control signals. The direction of the arrow indicates the flow direction of the hydraulic fluid. This pump allows automatic control of the actuator speed in proportion to load, enhancing system efficiency.
Bidirectional Variable Hydraulic Pump
The bidirectional variable hydraulic pump is the most versatile. It not only provides oil in both directions and variable flow, thus making your hydraulic system more flexible and efficient, reducing energy losses. Its symbol on drawings reflects both bidirectional and variable flow properties, so it is the best option for systems with a wide range of variations in loads and frequent operations.
How to Master Hydraulic Pump Symbols?
To master hydraulic pump symbols, first know what each of these graphics represents in a hydraulic system. Don’t just look at the symbol itself—knowing the behind-the-scenes operating mechanism is the secret to successfully reading hydraulic diagrams.
When you examine a hydraulic pump symbol, start with the direction of the arrow. The arrow, in addition to indicating the hydraulic fluid flow direction, also shows the direction of rotation of the pump. By the arrow, you will readily determine the running direction of the pump within the system.
Secondly, the symbol shows the flow type of the pump. For example, a plain arrow often designates a fixed-displacement pump with steady flow, while an adjustment-marked arrow indicates a variable-displacement pump whose flow is capable of adjusting according to system requirements. Understanding these facts aids you in understanding the working principles of the hydraulic pump as well as the operational rules of the whole hydraulic system.
FAQ
- Where are hydraulic pumps used?
Hydraulic pumps are used in nearly every type of hydraulic machine you can imagine. A few examples include excavators, cranes, presses, and lift platforms—all of which rely on hydraulic pumps to deliver power and make precise, smooth motion.
- Can the symbol for the hydraulic pump tell me about the displacement of the pump?
Symbols of hydraulic pumps typically do not provide individual displacement values. They are primarily used to indicate the type of pump, flow behavior, and flow direction. To ensure accurate displacement, it is better to check the product guide, which will include detailed technical information.
- How do you distinguish between unidirectional and bidirectional pump symbols?
The easiest method is to count the number of solid triangles. There is one solid triangle in a unidirectional pump symbol, indicating hydraulic fluid flows in one direction only. Two triangles are indicated in a bidirectional pump symbol, which means the pump can supply fluid forward and reverse.
- How are fixed-displacement and variable-displacement pump symbols different?
Look for an arrow across the entire circle. Without it, it’s a fixed-displacement pump with constant flow. Without it, it’s a variable-displacement pump with variable flow.
- Why do pump symbols appear different on some hydraulic drawings?
This is typically due to variations in drawing conventions and standards. On the international scene, hydraulic system symbols follow ISO/DIN or ANSI standards with minor variations in detail representation. For example:
Some standards place the variable pump adjustment arrow alongside the pump body, and others incorporate it directly into the pump. Some standards call for rotation direction, but others do not.
Furthermore, engineers may incorporate personal bias when designing, such as differing symbol size or arrow orientation. Don’t worry, these differences will not typically make a difference in your ability to identify the pump.
Conclusion
The hydraulic pump is the prime mover that converts mechanical energy into hydraulic energy. Its basic principle is altering the volume of a confined chamber at regular intervals to draw fluid in and then discharge it with pressure. Through the definition and operation mechanism of a hydraulic pump, you are capable of understanding the overall working reasonability of a hydraulic system.
Symbols are the other main key to interpreting hydraulic pumps, describing complex structures in a basic and easy-to-understand format on diagrams. Knowledge of these symbols allows you to quickly recognize types of pumps, directions of flow, and whether a pump is variable displacement. This simplifies design, maintenance, and troubleshooting work.
If you would like additional information on hydraulic pump applications or need help selecting the right pump for your application, feel free to call on us. Our engineers offer one-stop solutions tailored to your requirements, saving you time and money.
