control valve

What is a pressure control valve and how does it work

What is a pressure control valve and what does it do

A pressure control valve can protect a system from the damages which is caused by excessive pressure. These valves can do the pressure control of a system an example for this is, using a line relief valve to limit the maximum allowable system pressure. These valves can be seen in hydraulic systems and they can protect the hydraulic system. In order to achieve the pressure control, pressure relief, and pressure regulation must be done. The pressure is developed in a valve, because of the restriction of the fluid flow. If the pressure in a system is not checked it could cause many damages to the system and this can cause a waste of time and money.

Why pressure control valve is used

  • It can limit the maximum pressure
  • Backpressure can be set
  • These valves would send a signal if the set pressure is reached
  • It can protect the pump or system from overpressure
  • It can unload a pump
  • These valves can set pressure at which oil enters a circuit

What are the functions of the pressure control valve

• Pressure reduction
• Load holding
• Sequential control
• Limits system pressure
• Controls the pressure in the selected section of the circuit
• Sequence motion
• Actuator sequence control
• Restrained movement control
• Reduced pressure control
• Pump unloading control

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

  • Pressure reducing valve
  • Pressure relief valve
  • Pressure safety valve

Pressure reducing valve (pressure regulators)

A pressure regulating valve will operate if there is a need for pressure reduction between two parts of a process. These valves are capable to reduce the liquid or gas pressure to a preset value. Pressure reducing valves can be seen in gas welding equipment.

This valve operation is depended on the balance between the fluid pressures acting above and below a piston and a spring force. The piston will close the valve if the low-pressure fluid and the spring force is higher than the high-pressure supply. If the low-pressure fluid force is decreased then the new fluid pressure and the spring force are less than the high-pressure supply fluid and the piston opens the valve. In order to keep the pressure under control, the valve will continuously open and close. The outlet pressure of the valve can be changed by changing the spring to a stronger or weaker one according to the need. In certain cases, an adjusting screw is used to change the spring force. Some reducing valves use more than one pistons and they also use diaphragms to increase the performance.

Pressure relief valve

These valves are used so that the overpressure of the liquid can be relieved. The operation of the pressure relief valve under normal conditions, like when the system pressure is normal the pressure relief valve will stay close with the help of a spring. The valve would open when the pressure of the fluid pushes the spring. The force or pressure required to open the valve is setpoint pressure. The setpoint pressure is the maximum normal operating pressure of the liquid. When the fluid pressure is more than the setpoint pressure then the valve will open slowly and the pressure is brought back to its normal level. Spring force is changed with the help of adjustment screw in case of different set point pressure.

Pressure safety valves

These valves can relive the overpressure of gasses and vapors, in this valve the setpoint is greater than the maximum normal operating pressure of the process fluid, but it is less than the maximum safe operating pressure of the equipment. If the fluid pressure is more than the setpoint pressure then the valve opens fully. So this can decrease the overpressure very fast and after that, the valve will close. The pressure at which the valve closes after the reducing process is less than the setpoint pressure. The difference between the opening and closing pressure is called blow-down. Most of the pressure control valves have their outlet diameter bigger than the inlet so that pressure can be reduced.

How to adjust a pressure control valve

The opening and closing of the pressure control valve are done with the help of piston and spring. The spring force can be changed so that the opening and closing speed of the valve can be changed. More than one piston is used to make the changes and in certain cases, diaphragms are used.

How to install a pressure control valve

While buying a pressure control valve we must make sure that all the protective plugs and wrapping are in place. Before fitting check that all the fittings and plugs are removed and check the seals that protect the valve setting are in place or unbroken. We must check that the information on the nameplate and identification tags against the work order.

What is a rupture discs

A rupture discs are also known as bursting disc and it is a pressure safety device. This device has no moving parts and it would break if a certain pressure level is reached and it would allow the fluid to flow quickly so that the pressure can be reduced. In certain cases, the rupture disc is fitted before the pressure control valve, and it is used when the fluid is very contaminated so the disc can protect the valve.

What are the applications of pressure control valves

  • These valves are used in many industries like a nuclear power plant, hydraulic power plant, and oil industry
  • These valves are used to control the gases, steam, and water system
  • These valves are used in boiler houses and distribution mains

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