How a Self Operated Pressure Reducing Regulator Works ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How a Self Operated Pressure Reducing Regulator Works

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A self operated pressure reducing regulator is a mechanical device that is used to control and reduce pressure especially in natural gas plants. A pressure regulator is essentially a force balanced device that adjusts to changes in the system it is controlling. There are two types of pressure reducing regulators used in natural gas systems:
1. Self operated regulators
2. Pilot operated regulators
Both types of regulators are very common in the gas industry the self-operated regulators are general used in lower flow and lower pressure system, and are less expensive regulators. While the pilot operated regulators are generally use in higher flow situation, like city gates, large customers, industrial accounts etc and where you have higher pressure to control.

Basic Parts of a Self Operated Pressure Reducing Regulators
Self Operated regulators consist of three basic components:
1. A loading element. 
2. A measuring element and 
3. A restrictive element as shown below

Self Operated Pressure Reducing Regulator

As seen above, the loading element is typically a spring but it can also be a weight or pressure from some external source. When the spring is compressed, it exerts a loading force. The measuring element or diaphragm is connected to the process fluid (gas) that is being controlled and creates a force opposing the loading force. The restricting element or valve is connected to the spring and diaphragm assembly and regulates the flow through the regulator.

Operating Principle of Self Operated Pressure Reducing Regulators
In a self operated pressure regulator, as downstream system pressure decreases the spring force overcomes the force of the gas acting on the effective area of the diaphragm and the valve opens increasing flow into the system. When system pressure increases, the measuring force (the force of the system gas acting on the effective area of the diaphragm) overcomes the loading force (spring force) and closes the valve reducing flow into the system.