What are safety valves

definition Safety valve

A safety valve is a valve which automatically allows a quantity of the medium to flow out without the support of any energy other than that of the medium, so that a predetermined pressure is prevented from being exceeded, and which is designed so that it closes and prevents further flow of the medium when normal working pressure conditions are restored.

Overview of the Facts

Suitable media:
Liquids, air, gases and technical vapors, water vapor, warm water, hot water, solar
Materials:
Stainless steel, gunmetal, brass, nodular cast iron
Temperatures:
from -270 ° C to +400 ° C
Connections:
Flange: DN 20 to DN 100
Thread: G ¼ "to G 2"

The difference Safety valve - pressure relief valve

Whether a user is allowed to use a pressure relief valve or whether an approved safety valve must be used depends primarily on the type of application or system. Both types of valves serve to protect a system as the last safety instance. In the case of systems subject to acceptance or systems that fall under the European Pressure Equipment Directive, the valve must be equipped with the appropriate approvals and certificates.

Safety valves

  • Approved valves with TÜV and / or EC type examination

  • Normal lift or full lift opening / closing characteristics

  • Higher blow-off capacities than pressure relief valves

Pressure relief valves

  • Valves without approval (no safety function according to DGR)

  • Proportional opening / closing characteristics

  • Lower performance than safety valves

construction of a valve

Even if each series differs in the area of ​​safety fittings, the main components of each fitting are similar to the sectional view shown here. The optimal design of the components can only be achieved through flow simulations and comparison with complex function tests.

function of a valve

The function of a safety valve can be traced back to a simple balance of forces between compression spring force and medium force. When the system is at rest and when it is installed on the system in normal operation, the spring force of the valve is greater than the force of the medium and the valve seals the system tightly. If the set pressure of the valve is exceeded due to increased system pressure, the valve opens and allows the pressure to be relieved through the escape of the medium. After a pressure reduction in the system below the closing pressure, the valve closes tightly again.

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