What is a Pressure Reducing Valve?

Pressure reducing valves decrease the incoming high pressure of water into a lower and safer pressure for your Process. They are normally installed on the main  line next to the shut-off valve.

As the Fluid  flows through the valve, it passes through the diaphragm that is connected to a spring and reduces the pressure to the desired level as the fluid moves from the valve through the other side.

A reducing valve can also be set to any desired downstream pressure within its design limits. Once the valve is set, the reduced pressure will be maintained despite the changes in the supply pressure and system load variations.

Types of  Pressure Reducing Valve

Self-operated PRVs are the simplest type.  Relatively low cost and relatively accurate regulation.  Price and accuracy will vary by manufacturer.

Pilot-operated regulators use a pilot valve to amplify the signal to the main valve.  Pilot-operated valves provide greater accuracy and higher turn-down ratios.

Benefits in Steam Applications

Typical problems associated with controlling steam flows have generated many theories on how to improve the control loop; many of which are sophisticated and expensive.

A simpler approach might yield greater results in both temperature control and cost efficiency.  Remotely set dome-loaded PRVs enable the steam equipment to operate and respond more quickly to varying conditions.  The regulator allows more flow to pass more quickly upon sensing a loss of pressure, thereby reducing fluctuations in output temperature.

The benefits of this application can be measured in dollars.  Eliminating control valves, controllers, and other elements in the control loop represents a large cost savings.  Reducing the complexity of the control loop with regulators can increase output, reduce costs and simplify start-up and maintenance.

Advantages:

• Inexpensive.
• Small.
• Easy to install
• Very robust, giving long life with minimum maintenance.
• Tolerant of imperfect steam conditions.
• Self-acting principle means that no external power is required.

Disadvantages:

• Proportional only control.
• Proportional band is 30% to 40% of the upstream pressure.
• Wide proportional band means that maximum flow is only achieved when the downstream pressure has dropped considerably. This means that the reduced pressure will vary depending on flowrate.
• Limited in size
• Limited flowrate.
• Variation in upstream pressure will result in variation in downstream pressure.

Applications:

Non-critical. And critical moderate load applications with constant running flowrates,