Pressure Process Control

What is a Pressure Regulator and How does it work?

What is a pressure regulator?

The major purpose of a regulator is to match the flow of the medium which could be gas, steam, or liquid through the regulator according to the requirement of the medium for the system. It would keep the system pressure at the required pressure and thus would control the overpressure and it would prevent the problems which could occur in the system due to the overpressure. So the pressure regulator can be seen in many industrial applications like in pneumatic automation systems it is used to regulate compressed air.

What is the need for an air pressure regulator?

Most industrial plants use compressed air as the source for many devices in the plant. This compressed air would be used in conveyors, pneumatic operated devices such as Solenoid valves, Control Valves, etc. Air pressure regulators would control the pressure to the devices in the plant at each point of use of the airline.

How to choose the pressure regulator?

  • We should consider the operating pressure range for the inlet and the outlet
  • We should consider the medium which is to be regulated
  • Temperature range
  • Accuracy required
  • Required materials
  • Overpressure protection
  • Size and weight
  • Material that is used in the regulator
  • Minimum and maximum capacity
  • Safety options
  • Vent and body orientation

What is the difference between the pressure regulator and the control valve?

Regulators don’t need an external power source it is a control device that would utilize the energy from the controlled system. In the case of the control valve, it would need an external power source it would also require transmitting and control instruments.

What are the major functions of the air pressure regulator?

  • It would provide a constant outlet pressure
  • It would reduce the air pressure level to the industrial device from the pressure source
  • It would protect the industrial devices from overpressure

How does a pressure regulator operate?

pressure regulator

A pressure regulator has three functional elements pressure reducing element, a sensing element which could be a diaphragm or a piston and there would also be a reference force element and mostly it would be a piston. Mostly the working principle of the pressure regulators is the same. During the operation, the reference force which is created by the spring opens the valve. This valve opening would create pressure on the sensing element and this would close the valve till it is open just enough to maintain the set pressure. So here the reducing element is the valve and the piston is the sensing element. The reference force element would determine how much pressure is required for the system and according to it, the valve would open the reference force element would be a mechanical spring.

What is droop?

Droop can be defined as the drop in the outlet pressure below the original set point when the flow increases. This can also be caused due to changes in the inlet pressure. In case, if the inlet pressure increases then the outlet pressure decreases and vice-versa. We can determine the accuracy of the pressure regulator by checking the droop.

How can we determine the accuracy of the pressure regulator?

We could determine the accuracy of the pressure regulator by comparing the outlet pressure and the flow rate. If the flow rate increases then there should be a drop in outlet pressure and this process is called droop. We can determine the accuracy of the pressure regulator according to the drop the regulator creates over a range of flow. If the droop is less then the regulator has good accuracy.

What are the major types of pressure regulators?

Direct operated regulators

Direct operated regulators

This type of regulator is mostly used for low set pressures, this regulator would sense the downstream pressure by the internal pressure registration or the external control line. This downstream pressure would pressurize the spring and this would move the diaphragm and valve plug to vary the size of the flow path through the regulator. These regulators are mostly used for industrial and residential purposes.

Pilot operated regulators

Pilot operated regulators

This type of regulator is mostly used for high flow rates or where accurate pressure control is required. The major parts of this regulator are the pilot valve and the main valve. These regulators are capable to make changes downstream very quickly because the pilot is sensing the downstream pressure continuously. The pilot regulators are capable to handle pressure with flat line response. Mostly this type of regulator would use the two-path control, so the main valve diaphragm would respond quickly to the downstream pressure changes and due to this, an immediate correction in the main valve plug position can be achieved.

Precautions to be taken before maintenance of a pressure regulator

Before doing any maintenance of the regulator we should shut off the gas in the upstream and downstream from the regulator and also make sure that there is no gas under pressure inside the body by loosening the upstream and downstream connections. After completing all these checks for leaks. Make sure that the maintenance process is carried out by an experienced person otherwise it could badly affect the regulator and the process would be affected where this regulator is used.

How to install a pressure regulator?

  • It is used in natural gas
  • Automotive engines
  • Aerospace
  • Air compressors
  • Natural gas and mining industry

What are the advantages of pressure regulators?

  • We can use pressure regulators to control the pressure in air motors, spraying devices, fluidic systems, air logic valves, fluid power applications, and a lot more
  • Simplicity so there is little to go wrong
  • Economical
  • Springs can be wound in various thicknesses in spring-loaded type
  • It can be used for high flow applications
  • Certain types of pressure regulators can be controlled remotely

What are the disadvantages of pressure regulators?

  • Sensitive to shock and vibrations
  • Spring forces can vary due to compression in spring-loaded type
  • Large space is required while assembling
  • Aging can cause failure

What are the major issues with the air pressure regulator?

There are certain problems that are associated with pressure regulators some of them are

  • Internal component damage
  • Overpressure can cause a lot of problems to the regulator and also to the system in which it is used so overpressure protection must be done
  • If the downstream pressure is higher than the regulator’s pressure setting then it could damage a lot of internal parts
  • Air leak from the regulator bonnet could be another problem and this could because of a leaky bonnet or diaphragm. These parts should be repaired
  • if the diaphragm is broken then there would be a huge air leak so replace the diaphragm
  • In case of spring, failure replace it

What is the purpose of the control spring in pressure regulators?

Regulators use a control spring, to act on the diaphragm to regulate the air pressure. The rating of the control spring would determine the pressure adjustment range of the regulator.

How can we determine if the selected pressure regulator is suitable for our application?

Before choosing a pressure regulator we must determine the downstream equipment flow and pressure requirements to properly size the correct regulator for our application.

Is it possible for a pressure regulator to maintain a constant output pressure during variations in the input pressure?

Pressure regulators can maintain a constant output pressure regardless of variations in the input pressure and downstream flow requirements.

What is relieving and non-relieving pressure regulators

We can adjust the relieving regulators from high pressure to low pressure and it can be done even in a dead-end situation. The relieving regulators would allow the excess downstream pressure to be exhausted. In the case of the non-relieving regulator, it won’t allow the downstream pressure to escape, the trapped air needs to be released in some other way.

Can we use pressure regulators as a shut-off device?

We should not use pressure regulators as a shut-off device, because there will always be a small amount of leakage across the seat. We can use a shut-off valve in downstream of the regulator in case isolation is required.

What is creep in pressure regulator?

It is the increase in the outlet pressure due to lock up, mostly it is a long-term slow pressure increase. This shows the leak in the regulator and it should be immediately removed for service.

Can we use pressure regulators to regulate the flow?

Pressure regulators are used to control the pressure they can’t be used to control the flow.

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