RELIEF VALVE
RELIEF VALVE
RELIEF VALVES ARE USED TO CONTROL PRESSURE IN SYSTEMS, SUCH AS THOSE THAT USE COMPRESSED AIR OR FLUID. THEY OPEN IN PROPORTION TO THE INCREASE IN PRESSURE, WHICH HELPS PREVENT DAMAGE OR CATASTROPHIC FAILURE. HERE ARE SOME ADVANTAGES AND DISADVANTAGES OF RELIEF VALVES:
ADVANTAGES
- RELIABLE: : WHEN PROPERLY SIZED AND OPERATED, RELIEF VALVES ARE RELIABLE.
- VERSATILE: : RELIEF VALVES CAN BE USED FOR MANY SERVICES.
- PROTECTS SPRING: : IN CORROSIVE OR DIRTY SERVICE, A BELLOWS PROTECTS THE SPRING FROM PROCESS FLUID.
DISADVANTAGES
- BELLOWS FATIGUE: : THE BELLOWS CAN FATIGUE, ALLOWING PROCESS FLUID TO ESCAPE THROUGH THE BONNET.
- BACK PRESSURE: THE RELIEVING PRESSURE IS AFFECTED BY THE BACK PRESSURE, WHICH IS THE PRESSURE AT THE OUTLET OF THE VALVE. CHATTER: IF THE BUILT-UP BACK PRESSURE IS TOO HIGH, THE VALVE CAN CHATTER.
- SET POINT DRIFT: THE SET POINT CAN DRIFT OVER TIME AFTER INSTALLATION.
OTHER CONSIDERATIONS FOR RELIEF VALVES INCLUDE:
RAIN CAP: A RAIN CAP CAN PROVIDE A VISUAL INDICATION WHEN THE RELIEF VALVE OPENS.
SELF-OPERATED RELIEF VALVE: A SELF-OPERATED RELIEF VALVE CAN THROTTLE AT LESS THAN FULL RELIEF AND IS MORE STABLE THAN A POP RELIEF.
TESTING FREQUENCY: THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME), NATIONAL BOARD INSPECTION CODE (NBIC), AND STATE AND LOCAL JURISDICTIONS MAY SET REQUIREMENTS FOR TESTING FREQUENCY.
