Safety valves protect a pressure vessel or installation against pressure rise. The safety valve automatically bleeds the medium (agent) when the pressure increases 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 be of an open construction – atmospheric discharge, where the medium is released directly to the atmosphere. These atmospheric discharge safety valves are used for air, inert gases, non-toxic and non-flammable gases. The medium from the enclosed construction (angle type) valve is released to discharge piping. Suitable for hazardous media, steam, fluids, hazardous gases and low temperature gases. A gastight version and version with a bellow used when counter pressure occurs, are available as well.
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 sectors of industry, in air compressors, pressure vessels, silos, steam boilers, tankers, autoclaves, pressure cylinders, cryogenic installations, chemical plants, shipbuilding industry, offshore industry, food and pharmaceutical industry.
The precise value of valve working pressure is set by the manufacturer, then the valve is sealed. The set pressure value is usually imprinted as marking on the valve body. After the valve working pressure range is chosen, the required 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. Depending on the lifting device, it can be a lever, a twist-type mechanism (by turning a nut), stem. Repairs must only be performed by the manufacturer.