control valve

What are the types of pressure control valves and how does it work

What are the types of pressure control valves

The major function of a pressure control valve is to protect the system from overpressure. This pressure could occur due to the decrease in fluid demand or it can also happen because of the surge which could cause during the opening and closing of the valve. These valves can control and regulate the pressure in a fluid power system and these valves are smaller in size so it can be installed without any problem of consuming space. By using a pressure control valve in a system we can ensure the proper and safe function of a system. These valves are capable to remove pressure from a vessel, pipeline. Some of the pressure valves can be used to maintain the pressure in the required limit. Pressure control valves are mostly relief valves and they can release the pressure by lifting a nozzle. Mostly the relief valves are installed between the pressure source and the system isolation valve. Pressure control valves are used in systems that have hydraulic and pneumatic systems so that they can protect the system from overpressure.

The major types of pressure controlling valves are

  1. Pressure regulators
  2. Counterbalance valves
  3. Sequences valves
  4. Unloading valves
  5. Safety valves
  6. Relief valves
  7. Brake valve

Why do we need to use a pressure control valve

  • It is used to limit the maximum pressure
  • Backpressure can be set by using this valve and it would pass a signal when a certain pressure is reached
  • It can protect the pump from overpressure
  • It can unload system pressure
  • It will decrease the main circuit pressure to a lower level in a subcircuit

Types of pressure control valves and how it works

Pressure regulators

Pressure regulators are also known as pressure reducing valve, it can keep the output pressure at a set value. These valves can control the pressure in the line. These valves are used in hydraulic systems so that they can maintain the reduced pressure in the hydraulic system. The outlet pressure is controlled by a spring-loaded spool. The spring is set to control the pressure so if the outlet pressure is less than the spring setting, then the spool will change its position and thus the flow takes place from the inlet to the outlet. The spool will move back to its position if the outlet pressure increases, there is an internal passageway that would allow the outlet pressure to the spool end opposite the spring. The spool will move back to its position only if the outlet-pressure balances the spring force.

How to select a pressure regulator

  • According to the normal line pressure
  • According to the maximum required flow at a regulated pressure
  • According to the required pressure precision level
  • It must be selected according to the maximum and minimum regulated pressure
  • While selecting a pressure regulator we must consider the adjustment frequency and also need to consider the location and application.
  • It should be selected according to the required pipe size

Counterbalance valve

The counterbalance valve allows flow in one direction and restricts the flow in another direction. This valve would maintain the backpressure so that it can prevent the load from falling. These valves are also known as load holding valves and these valves are installed between the directional control valve and a cylinder. This valve would provide a hydraulic resistance to the cylinder. These valves can maintain a set pressure in a part of the circuit and by doing this it can balance the weight or force. These valves are used with a single-acting cylinder, which lowers the load. So when the pump is not working these valves can prevent the load from falling down and it is done by maintaining a back pressure against the load. When the pump starts working the fluid will flow through the check valve and it would only provide less resistance. The counterbalance valve would open when the directional control valve moves to the right and it would provide resistance to the flow and this resistance can be controlled by a spring and by this the valve prevents the load from quickly falling.

Sequence valve

These valves can control the operation between two branches of a circuit. These valves control the fluid flow in a sequential manner and they can control the operational sequence of two actuators. The flow can be diverted in a sequential manner by this valve. This valve can control the pressure in a valve and it can sense the inlet pressure. By using a sequential valve we can be certain that pressure level is achieved in one branch before activating another one. So the fluid flow to the next part is only done after completing the first part. During the normal condition, the sequence valve would be closed and permits the flow until the valve reaches its pressure level. So when the first section is completed the pressure would rise in this section and it would be sensed by the pressure sensing passage, because of this the pressure in the spool increases than the spring pressure and the valve spool shifts. Then the flow is transferred to the next circuit.

Unloading valve

These valves can save energy by unloading a pump when there is no need for flow. So by using this valve the pump can be operated at minimum load. These valves are used in hydraulic circuits it can transfer the excess fluid to the tank and by doing this it can decrease the heat and save energy. The port of the unloading valve will be connected to the line that is to be unloaded. The pressure is sensed by using the pilot port and sends the signal to unload the flow. So when the system pressure reaches the setting pressure then the spool will be lifted. Then the flow from the pump to the tank takes place.

Brake valve

The brake valve can compare the pressure in the inlet and outlet which is done with the help of sense lines. The motor would turn if there is pressure in the inlet port. The piston would move against the spool because of the inlet pressure and the valve would be open so the motor movement can be achieved. So when the pressure is decreased at the inlet port the piston would move and the spring spool would apply pressure to decrease the motor movement and its load.

SAFETY VALVE

Relief valve

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