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A.0500.551 – IM-TGMAG/02.00 EN (02/2008)
3.17.1 Definition and working principle
The safety relief valve built on top of TopGear pumps is designed to protect the pump against over-
pressure. It limits the differential pressure (or working pressure) of the pump.
It is a spring-loaded pressure relief valve that opens rapidly by pop action when the working
pressure increases to the set pressure on which the spring is set in advance.
The safety relief valve built on top of the TopGear pump may not be used permanently opened
because the liquid will be heated up very fast by viscous friction losses. All power input will go to the
pumped liquid that circulates in the pump when the safety relief valve is opened and no discharge
flow is given.
The single safety relief valve protects the pump only in one direction of flow.
Heating
The spring casing of the safety relief valve can by provided by a welded jacket with thread
connections to heat the area around the spring. The valve body is heated together with the pump
because it is mounted directly on the pump casing.
3.17.2 Materials
The safety relief valve casing is made of grey cast iron (G) or stainless steel (R). The option heated
spring casing is only available for cast iron pumps; in this case the spring casing is made of steel.
The internals of the safety relief valve i.e. valve, spring, spring plates and adjusting bolt, and nut is
made of stainless steel.
3.17.3 Pressure
Safety relief valves are divided into 4 working pressure classes i.e. 4, 6, 10 and 16 indicating the
maximum working pressure for that valve. Each class has a standard set pressure at 1 bar above the
indicated maximum working pressure. The set pressure can be set lower on request never higher.
3.17.4 Heating
The weld on spring casing is provided with 2 thread connections. Flange connections are not
available.
Maximum temperature: 200°C
Maximum pressure: 10 bar
Working pressure class 4 6 10 16
Standard set pressure (bar) 5 7 11 17
Working pressure range (bar) 1 – 4 3 – 6 5 – 10 9 – 16
Set pressure range (bar) 2 – 5 4 – 7 6 – 11 10 – 17