Hydraulic pumps are widely used in engineering and mechanical fields. Did you know that hydraulic pumps are divided into single-acting and double-acting types? What are the differences between them?

In this article, TorcStark provides a comprehensive introduction to the distinctions between single-acting and double-acting hydraulic pumps. The primary content includes their working principles, advantages, disadvantages, differences, and practical applications.

Single acting hydraulic pump

Working principle

Single-acting hydraulic pumps only produce hydraulic pressure in one direction. It is designed to provide fluid flow and pressure during one stroke or its direction of operation.

Single-acting hydraulic pumps are mainly composed of the following and parts, including:

  1. Hydraulic Oil: It transmits energy in the hydraulic system.
  2. Hydraulic Cylinder: This is a device, consisting of a piston and cylinder, used to convert hydraulic pressure into mechanical force or displacement.
  3. Single-acting hydraulic pump: usually has one inlet and one outlet. It is a device that sucks fluid from one place (such as an oil tank), amplifies its pressure and pushes it to a hydraulic cylinder.

Work process:

Suction phase (push rod return): During the initial phase of a single-acting hydraulic pump, the piston moves back, creating an area of negative pressure. This will cause hydraulic oil to be drawn into the interior of the pump from the tank or a low pressure area of the hydraulic system.

Discharge phase (rod advance): When the hydraulic pump’s push rod is pushed forward, it compresses the liquid in the pump. This causes hydraulic oil to be pushed into the cylinder through a one-way valve. At this time, the piston in the hydraulic cylinder will be pushed forward to perform mechanical work.

Advantage

It plays an important role in specific application scenarios, such as applications that require unidirectional mechanical motion, such as lifting, pushing, squeezing, etc.

Disadvantages

Single-acting hydraulic pumps can only generate hydraulic pressure and mechanical movement in one direction.

At the other end of the cylinder, an external force is usually required to return the piston to its original position.

Double acting hydraulic pump

Working principle

Double-acting hydraulic pumps generate hydraulic pressure in both directions. It is designed to provide fluid flow and pressure during its extended and retracted strokes of operation.

The double-acting hydraulic pump is mainly composed of the following and parts, including:

  1. Hydraulic Fluid: A common hydraulic oil that transmits energy in a hydraulic system.
  2. Hydraulic Cylinder: A hydraulic cylinder consists of a piston and cylinder and is used to convert hydraulic pressure into mechanical force or displacement.
  3. Double acting hydraulic pump: It usually has two inlets and one outlet. A device that can generate hydraulic pressure in both directions of a hydraulic cylinder, usually with two working strokes.

Work process:

Push rod forward phase: When the push rod of a double-acting hydraulic pump is pushed forward, it compresses the fluid inside the pump. This causes hydraulic oil to be pushed through a one-way valve into one port of the cylinder, which pushes the piston forward, performing the mechanical work.

Push rod return stage: When the push rod returns to the initial position, the hydraulic pump will create a negative pressure, so that the hydraulic oil will be sucked into the other port of the hydraulic cylinder through another one-way valve. At this time, the piston of the hydraulic cylinder will be pushed to the rear.

Advantage

The advantage of a double-acting hydraulic pump over a single-acting hydraulic pump is that it can generate hydraulic pressure in both directions, with greater efficiency and flexibility, enabling a wider variety of mechanical movements.

Double-acting hydraulic pumps are suitable for applications requiring mechanical motion in both directions, such as lifting and lowering, pushing and pulling, compressing and stretching, etc.

The difference between single-acting and double-acting hydraulic pumps

  1. Difference in working principle: Single-acting hydraulic pumps can only generate hydraulic pressure and mechanical movement in one direction. When its push rod is pushed, the compressed fluid pushes hydraulic oil into the hydraulic cylinder, which pushes the piston to perform mechanical work. Double-acting hydraulic pumps are capable of generating hydraulic pressure and mechanical movement in both directions. When the push rod advances, the hydraulic oil is pushed to one port, pushing the piston forward; when the push rod is retracted, the hydraulic oil is pushed to the other port, pushing the piston backward.
  2. The difference in the way hydraulic pressure is generated: single-acting hydraulic pumps only generate hydraulic pressure in one direction. Double-acting hydraulic pumps are capable of generating hydraulic force in both directions, offering a wider range of mechanical motion options.
  3. Advantages and disadvantages: single-acting hydraulic pump, simple structure, low cost. In certain applications, there is sufficient functionality. However, it is limited to one-way movement and cannot achieve two-way operation. An external force is required to push the piston back to its original position. Double-acting hydraulic pump: capable of two-way mechanical movement, providing greater flexibility. It is more suitable for applications that require multiple sports modes. But the structure is complex and the cost is high.
  4. Fields of application: Single-acting hydraulic pumps are suitable for applications that require only one-way mechanical movement, such as pushing, squeezing, etc. Double-acting hydraulic pumps are suitable for a wide range of applications requiring mechanical motion in both directions, such as lifting and lowering, pushing and pulling, compressing and stretching, etc.

Practical application

Application cases of single-acting hydraulic pumps:

  1. Automatic door opening and closing system: In an automatic door system, it is usually only necessary to realize the opening or closing of the door in one direction. A single-acting hydraulic pump can be used to push the door body to open or close the door, while on the other side of the door, gravity or other external force can be used to return the door to its original position.
  2. Punch press operations: Punch presses generally require pressure to be applied in one direction to perform stamping operations, such as cutting, punching, etc. of metal materials. A single-acting hydraulic pump can be used to apply the required one-way pressure to complete the press work.

Application cases of double-acting hydraulic pumps:

  1. Car jack: In car maintenance, the jack needs to realize the bidirectional movement of lifting and lowering. Double-acting hydraulic pumps can be used to raise and lower the jack, providing a wider range of mechanical motion options.
  2. Excavator Arm Operation: The arm of an excavator requires upward and downward motion to complete excavation. Double-acting hydraulic pumps can be used to control the bi-directional movement of the excavator arm for more complex operations.
  3. Hydraulic push-pull machines: In the industrial field, hydraulic push-pull machines typically require pressure to be applied in two directions to push or pull a workpiece. A double-acting hydraulic pump can be used to provide the required bi-directional pressure for the push-pull machine.
  4. Lifting Platforms: Lifting platforms in commercial and industrial locations need to provide two-way motion when raising and lowering. Double-acting hydraulic pumps can be used to control the lifting process of the lifting platform.

Conclusion

To sum up, we have compared single-acting and double-acting hydraulic pumps from various aspects. Therefore, it can be concluded that single-acting and double-acting hydraulic pumps each have their own advantages and fields of application. In actual engineering needs, the appropriate type of hydraulic pump should be selected to ensure efficient and reliable operation.