Pressure Relief Valves: Limiting Pressure
As liquid or gas flows through a system, it is important that supervisors have control over how much liquid or gas flows to certain areas, and when that flow actually takes place. Pressure relief valves help to control the flow of liquid or gas, while also allowing the pressure to be limited according to system and factory needs.
If a liquid or gas happens to have a high pressure when it is leaving one area, that amount of pressure may not be well received in a different area of the system. These are excellent locations for the installation of pressure relief valves. The area of the system after the relief valve may have certain sensitive equipment that will not function well if it is subjected to high volumes of pressurized liquid or gas. This equipment can be protected with pressure relief valves.
The pressure relief valves in a system work to release extra pressure. The pressurized fluid that enters one of these valves is provided with a flow passage with actually leaves the main system. This provides an outlet for the extra pressure, before it enters areas with sensitive equipment and possibly causes damage to occur.
The relief valve is typically designed to become the main path for a liquid or gas during situations where the pressure sensors pick up on the fact that substances flowing into a certain area are at a pressure too high to be allowed to continue past a certain point. The adjustment in flow to a pressure relief valve causes the media in the system to enter the flare header, which is also known as the relief header. This area is the extra piping system, and it is not a portion of the main pipeline. Extra pressure could be burned off through the process of combustion within the flare header.
After the blowdown has been achieved, the media in the flare header is permitted to enter the rest of the system. The blowdown refers to the amount the pressure needs to drop before integration can occur with a valve reseat. The most common amounts of blowdown that are required fall between two and twenty percent. For some factories that have a variety of applications, it may be prudent to shop for pressure relief valves that also contain adjustable blowdowns. These can be set to respond to different operations and conditions within a system.
Pressure relief valves that provide an outlet to the open air are recommended for some systems that contain high-pressure substances. If the outlet portion of the relief valve enters into another portion of the piping system, that area will experience pressure build-up. In certain instances, a bypass valve is installed in conjunction with a pressure relief valve. This type of valve returns to the main system the portions of a substance that were discharged in the process of removing heavily pressurized materials. The bypass valve allows for all of the substances to be used in the course of operation, without anything getting wasted from pressure relief actions.
