Vacuum relief valves
Process equipment, pipelines and atmospheric storage tanks must be protected against being subjected to an internal vacuum (i.e., pressures below 0 kPag) that is lower than the equipment can withstand. In such cases, the Engelsberg vacuum relief valves (also called vacuum vent valves) are installed and set to open at a predetermined vacuum set pressure limit. This is to admit atmospheric air into the process equipment, pipeline or atmospheric storage tank, to control the amount of vacuum. These Engelsberg valves are spring operated, with metal to metal seat.
