Every piece of equipment in a process system should be carefully considered and specified. Arguably the most important safety-related process equipment is the over-pressure control devices. This is considered the “fail-safe” in a system. These devices automatically release a substance from a boiler, pressure vessel, or other systems, when the pressure or temperature exceeds preset limits. Two common types of these devices are Pressure Relief Valves and Rupture Discs.
Safety Valves are specialized, typically spring-loaded valves that are designed to open at a set pressure to relieve the pressure in a system to protect the equipment, system, and human life.
Rupture discs are another common type of safety device. They have no moving parts and are a type of sacrificial part because it has a one-time-use membrane that fails at a predetermined differential pressure, either positive or vacuum. They can be used as single protection devices or as a secondary relief device for a conventional safety valve; if the pressure increases and the safety valve fails to operate or can’t relieve enough pressure fast enough, the rupture disk will burst. Rupture disks are very often used in combination with safety relief valves, isolating the valves from the process, thereby saving on valve maintenance and creating a leak-tight pressure relief solution.
All ASME-code stamped vessels and exchangers require a pressure relief device or system, set no higher than the equipment MAWP. When designing a piece of pressure equipment (tank, pressure vessel, heat exchanger, etc.), important factors to keep in mind are the best location, sizing (for liquid systems, valves can typically be smaller, but with vapor systems, sometimes very large valves are required in order to flow the necessary amount of gas to protect the system), reaction forces and, of course, materials of construction.
Speak with your design engineers and equipment providers to ensure you include the proper details in your safety system and let us know how Ward can be a resource for you during the early stages of design.
