Safety valves

Safety valves – general information

Safety valves protect a pressure vessel or system against pressure surges. The safety valve automatically releases the medium (agent) when the pressure rises above the set pressure value (set pressure). After the pressure levels off below the set pressure, the valve closes and the medium stops bleeding. The safety valves can have an open construction – atmospheric discharge, where the medium is released directly to the atmosphere. These open discharge safety valves are used for air, inert gases, non-toxic and non-flammable gases. The medium from enclosed safety valves (angle type) valve is released to discharge piping. They are suitable for hazardous media, steam, fluids, hazardous gases and low temperature gases. A gas-tight version and a version with a bellow are used when there is back-pressure in the discharge system.

Depending on the type, version and nominal diameter of the valve, the set pressure is in the range from a couple to several hundred bar.

The safety valves are used in all industries, in air compressors, pressure vessels, silos, steam boilers, tankers, autoclaves, pressure cylinders, cryogenic systems, chemical plants, shipbuilding industry, offshore industry, food and pharmaceutical industry.
The precise value of valve working pressure is set by the producer, then the valve is sealed. The set pressure value is imprinted as a marking on the valve body. Once the range of the valve working pressure is selected, the set pressure value must be determined. The diameter of a hose supplying the system equipped with the safety valve must not be smaller than the DN of the valve. Also, the pressure drop between the supplying hose and the valve must not exceed 3%. In order to check if the valve works properly, carry out a functional test either by turning a nut (twist-type mechanism) or by lifting either the lever or stem, depending on the lifting device. Any repairs can only be carried out by the manufacturer.