# Relief Valve and Bursting Disk

A relief valve is a type of valve used to control or limit the pressure in a system which can build up due to abnormal system operating conditions or instrument/equipment failure. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system. The relief valve is designed or set to open at a predetermined set pressure to protect a system from being subjected to pressures that exceed its design limits. When the set pressure is exceeded, the relief valve becomes the path of least resistance as the valve is forced open and a portion of the fluid is diverted through this auxiliary route. When modelling relief valves, users have the option of manually selecting the size of the orifice, or allowing FluidFlow to size the orifice based on the design system operating conditions. A bursting disk is a non-reclosing device that is designed to rupture or "burst" at a predetermined pressure, thus relieving a system of a dangerous build-up of pressure or vacuum. Bursting disks react quickly to overpressure conditions. This rapid response is crucial in applications where immediate pressure relief is necessary to prevent equipment damage. When modelling bursting disks, users have the option of defining the certified resistance coefficient "Kr". The bursting disk is treated as a "fitting" and uses the Resistance to Flow Method to estimate the frictional losses.