Master-Martyr Valve Arrangements

Electric actuator for industrial valves.
Image courtesy Rotork

Some industrial fluid flow applications are best served with what is known as a master-martyr valve set. Let's look at this arrangement and how it is used.

Valves are used to regulate flow. They are also applied to isolate portions of a fluid system by providing positive leak free shutoff. A master-martyr valve set utilizes two valves, with the performance of each targeted at differing performance goals. By coordinating the operation of the two valves, operational benefits accrue.

The master valve serves as the isolating valve. It will be located upstream of the martyr valve. The master valve provides fully open or fully closed operation and is commonly selected to accommodate the most severe operating condition anticipated in the system. Usually, this valve is normally open and is designed to contribute little to no pressure drop to the fluid flow. A good example is a full port metal seated ball valve. It offers very low pressure drop, substantial resistance to system pressure or heat, and can be driven from fully open to closed positions quickly.

The martyr valve provides flow regulation or throttling and is not intended to be the positive means of shutoff for the fluid flow. This valve will experience a range of pressure drop, possibly some flashing, or other conditions that, along with the frequent repositioning applied to the valve, will serve to produce wear and tear on the mechanism. Generally, the martyr valve is expected to wear out from normal operation and need servicing or replacement. The master valve, located upstream, serves as a point of isolation that allows the martyr valve to be easily serviced.

The overall goal is to operate the master valve as little as possible and expose it to the lowest possible pressure drop. Generally, this will call for the master valve to be opened first and closed last.

There are numerous potential applications for this valve arrangement. Smart actuators can function within the control system by delivering information about valve position and service level, as well as responding accurately to system commands. Share your fluid flow control challenges and applications with valve automation specialists. Leverage and effective solution by combining your own knowledge and experience with their product application expertise.

High-integrity Pressure Protection System (HIPPS) Valves

A HIPPS (high-integrity pressure protection system) is a category of "instrumented system" designed to prevent an over-pressurization condition at a process plant.

For oil, gas and chemical producers, loss of containment is a critical matter.  Over-pressure on a tank, vessel or pipeline can potentially cause explosive, flammable, toxic or hazardous chemicals to be released causing possible loss of life or adverse effects on the environment. Loss of containment can also have huge negative effects on the plants bottom line.

HIPPS will shut off the source of the high pressure before the design pressure of the system is exceeded, as opposed to a relief system which will open an alternative outlet for the fluids in the system once a set pressure is exceeded. A relief system attempts to remove any excess inflow of fluids for safe disposal, where a HIPPS is designed to stop the inflow of excess fluids and containing them in the system.  Conventional relief systems are increasingly frowned upon because they typically vent, flare or discharge hazardous or toxic fluids in to the environment.

HIPPS valves are used as the final part of an instrumented system intended to prevent an unacceptably high pressure occurring in downstream equipment. They are always arranged to fail closed and spring/hydraulic actuators are usually the only practical alternative for operation.

You can see a full application note on HIPPS relating to valves and ancillary systems here.