Engineered Control Valves, Safety Devices & Process Instrumentation
 

Pilot Operated Relief Valves

It is a common question asked amongst process engineers on why use a pilot valve for a particular application ? The following article I hope will answer this question and provide some insights into the different types of pilot valves available on the market today and their many features and benefits.

Why use a pilot valve ?

Pilot valves operate on a very simple set up. A sensing line, usually connected into the inlet piping, is connected into the pilot control. Another line is piped from the pilot control into the top of the main valve assembly. The pilot, which contains a small spring assembly, is set at a certain set pressure. During normal operation the inlet pressure passes through the sensing line through the pilot and continues into the dome of the main valve. The inlet pressure in effect is placing pressure onto the piston inside the main valve to keep the valve closed. At set point the spring inside the pilot causes a small piston to slide down allowing the inlet pressure sitting on top of the main valve piston to relieve through the pilot’s exhaust. This causes the main inlet pressure to be relieved through the main valve. The diagrams below illustrate this principle.

There are two main types of pilot control operation:





There are two main types of pilot control operation:
• Pop action.
• Modulating.

Have a look at the following diagram which illustrates how pop action pilots open the main valve fully at set point whilst modulating pilots open the main valve according to relief demand.

These two points are clearly summarized in the following diagrams.

Consolidated is the only relief valve manufacturer that offers the ability to retrofit an existing spring loaded relief valve into a pilot valve. Any 1900 series Consolidated spring loaded relief valve can be converted into a 2900 series pilot valve that will give you all of the benefits a pilot valve can offer.

Powerflo - Consolidated have the experience and safety and relief valve product range to meet your requirements. Just ask Shell who are enjoying the benefits of using Consolidated pilot valves for their recent clean fuels upgrade.

For more information on Consolidated pilot valves or any other safety and relief valve requirements you have feel free to contact one of our sales offices located around Australia.

Barry Herrett.
Product Manager – Safety & Relief Valves & Power Products.