CONTROL AND SMART VALVES
Don ’ t size safety valves based on
Basing safety valve capacity solely on outlet connection size rather than required flow rate can lead to dangerous overpressurization of protected vessels .
By Artur Cardozo Mathias
outlet diameter
About the author Artur Mathias is in Industrial Mechanical and Chemical Technician and a Member ISA . Now a consultant , he has been active since 1985 in the maintenance , inspection , specification and sizing of valves . Arthur provides training and technical courses , and is the author of the book Válvulas : Industriais , Segurança e Controle .
An installed pressure relief valve . Photo by David Sear
A serious error that we have seen is the specification of the safety valve based on the dimensions ( gauge ) of the connection ( whether threaded , flanged or welded ) of the equipment outlet ( pressure vessel , mainly ), to which the valve will be installed . Specifying , selecting and installing safety valves based only on outlet size rather than required flow rate is a serious error some users make . It can lead to dangerous pressure accumulation beyond safe limits due to high inlet pressure drop when the installed valve is undersized . This causes restricted flow through the valve nozzle . For pressure vessels , the maximum allowable pressure accumulation is 10 % or 3 psi above set pressure , whichever is greater , when
28 Valve World March 2024 www . valve-world . net