Definition of a safety valve

A safety valve is a valve which automatically, without the assistance of any energy other than that of the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to reclose and prevent further flow of fluid after normal pressure conditions of service have been restored.

Atmospheric discharge safety valves

Overflow and pressure control valves

TÜV/CE safety valves angle-type

Safety valves with flange connections

Overview of the facts

Medium:
Liquids, Luft, Air, gases and vapours, Steam, Warm water, Hot water, Solar heating systems

Materials:
Stainless steel, Gunmetal, Brass, Spheroidal graphite cast iron

Temperatures:
-270 °C to +400 °C

Pressures:
0,2 to 630 bar

Connections:
Flange: DN 20 to DN 100
Threaded: G ¼" to G 2"

The Difference between safety valve and pressure relief valve

Whether a plant operator is allowed to use a pressure relief valve, or if he must use a certified safety valve depends primarily on the type of application or plant. Both valve types are intended to be the last safety device in a system. In the case of systems or plants requiring official approval or which fall under the European Pressure Equipment Directive (PED), the valve must hold corresponding approvals and certifications.

Safety valves

Certified valves with TÜV / PED and/or CE Type Test Approval
Normal lift- Full lift opening / closing characteristic
Higher blow-off capacities than pressure relief valves

Pressue relief valves

Valve without certification / approval ( without safety function according to PED )
Proportional opening- / closing characteristic
Lower blow-off capacities than safety valves

Construction of a safety valve

Even if each safety valve series is different, the main components are similar to those shown in this cross-sectional diagram. An optimal design of the components is achieved by means of flow simulation programs and intensive functional tests.

Functioning of a safety valve

The function of a safety valve is based on a simple balance of forces between the force of the pressure spring and that of the medium. In the closed position, which is the normal position of the valve when installed on the plant, the spring force is greater than the force of the medium and the valve seals the plant tight. In case the set pressure of the valve is exceeded due to an increase in the plant pressure, the valve opens to relieve the excess pressure by blowing-off the medium. After excess pressure in the plant has been relieved below the closing pressure, the valve closes completely.

Further information?

Here you will find answers to questions which we are often asked ("FAQ’s").

To the safety valves FAQ

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