Pressure Regulators: Function & Types

The main function of any gas pressure regulator is to match the flow of gas through the regulator to the demand for gas placed upon the system while maintaining the system pressure within certain acceptable limits. Generally, regulators are simpler devices than control valves. Regulators are self-contained, directed-operated control devices which use energy from the controlled system to operate whereas control valves require external power sources, transmitting instruments and control instruments.

Let’s consider a spring-controlled pressure regulator below:

A spring-controlled regulator is illustrated above. A spring-loaded diaphragm is pushed on by regulated gas pressure. If the regulated gas pressure starts to fall, the reduced pressure on the diaphragm causes it to move downward, thus opening a valve and allowing more high pressure gas in.

Types of Pressure Regulators

Pressure regulators may be classified into the following types:

• Pressure reducing regulators
• Backpressure regulators
• Pressure relief valves
• Pressure switching valves
• Vacuum regulators and breakers

Pressure Reducing Regulators

A pressure reducing regulator maintains a desired reduced inlet pressure while providing the required fluid flow to satisfy a downstream demand. The pressure which the regulator maintains is the outlet pressure setting (setpoint) of the regulator. Pressure reducing regulators are further categorised into direct-operated (self-operated) regulators and pilot-operated regulators.

Backpressure Regulators

A backup pressure regulator maintains a desired upstream pressure by varying the flow in response to changes in upstream pressure.

Pressure Relief Valve

A pressure relief valve limits pressure build-up (prevents overpressure) at its location in a pressure system; the relief valve opens to prevent a rise of internal pressure in excess of a specified value. The pressure at which the relief valve starts to open pressure is the relief pressure setting.

In actual fact, pressure relief valves and backpressure regulators are similar devices. The name is usually determined by the application.

Pressure Switching Valves

Pressure switching valves are used in pneumatic logic systems. These valves have either two-way or three-way switching. Two-way switching valves are used for ON/OFF service in pneumatic systems. Three-way switching valves direct inlet pressure from one outlet port to another whenever the sensed pressure exceeds or drops below a preset limit.

Vacuum Regulators and Breakers

Vacuum regulators and breakers are used to control vacuum. A vacuum regulator maintains a constant vacuum at the regulator inlet with a higher vacuum connected at the outlet. During the operation, a vacuum regulator remains closed until a vacuum decrease (a rise in absolute pressure) exceeds the spring setting and opens the valve disk.

A vacuum breaker prevents a vacuum from exceeding a specified value. During operation, a vacuum breaker remains closed until an increase in vacuum (a decrease in absolute pressure) exceeds the spring setting and opens the valve disk.

Related articles:

• Pressure Control Valve Operation
• Pneumatic Actuators
• The Parts and Functions of a Valve
• Electric Solenoid Actuator – Features & Operation
• Manipulating Devices & Actuators in Process Instrumentation