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What is a Pressure Regulator?

A pressure regulator is a valve that controls the pressure of a fluid or gas to the desired value. Regulators are used for gases and liquids and can be an integral device with a pressure setting, a restrictor, and a sensor all in one body, or consist of a separate pressure sensor, controller, and flow valve such as the Fisher MR 95. Whereas, the Fisher 92 & 1098 EGR would use a downstream sensing line for feedback to a pilot Regulator to control the much larger valve.

Types of Pressure Regulators

The pressure reduction regulator and the back-pressure regulator.

Pressure Control Valve/ Pressure Reducing Regulator

A pressure-reducing regulator is a control valve that reduces the input pressure of a fluid or gas to the desired value at its output. It is a normally-open valve and is installed upstream of pressure-sensitive equipment. The Fisher T205 would be ideal for tank blanketing.

Back Pressure Regulator/ Fisher Valves

A back-pressure regulator, back-pressure valve, pressure sustaining valve, or pressure sustaining regulator such as the Fisher MR98 is a control valve that maintains the set pressure at its inlet side by opening to allow flow when the inlet pressure exceeds the set value. It differs from an over-pressure relief valve in that the over-pressure valve is only intended to open when the contained pressure is excessive, and it is not required to keep upstream pressure constant.

They differ from pressure-reducing regulators in that the pressure-reducing regulator controls downstream pressure and is insensitive to upstream pressure. It is a normally-closed valve that may be installed in parallel with sensitive equipment or after the sensitive equipment to provide an obstruction to flow and thereby maintain upstream pressure.

Both types of regulator use feedback of the regulated pressure as input to the control mechanism, and are commonly actuated by a spring-loaded diaphragm or piston reacting to changes in the feedback pressure to control the valve opening, and in both cases, the valve should be opened only enough to maintain the set regulated pressure. The actual mechanism may be very similar in all respects except the placing of the feedback pressure tap.

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