Pressure Relief - Direct Acting

Pressure Relief Valves - Direct Acting.

Pressure Relief Valves are designed to automatically and quickly release excess system pressures according to pre-set levels to protect all upstream equipment. They are designed to stay closed until the upstream (back pressure) reaches or gets close to the manually pre-set safety setting of the relief valve. At this point, the valve will open very quickly to release the excess pressure downstream through the outlet port. When the system pressure has dropped back within the pre-set pressure setting of the valve, the valve will slowly close to prevent back pressure spikes or water hammer. The current retained pressure is displayed by a pressure gauge mounted on the top of the valve.

Pressure relief valves are not to be confused with back pressure or pressure sustaining valves, as pressure relief valves perform a fast safety pressure release function and are not designed to work in a constant open position to regulate back pressure.

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The RLT (Threaded) and RLF (Flanged) pressure relief valves have a range of manually fully adjustable pressure ranges from 0.5 to 10 bar or 7 to 20 bar and designed to work with inlet pressures up to 25 bar.

Pressure ranges are based on internal spring tensions or strength, where strong springs are better suited to accurately operate with higher pressure and loads, whilst weaker springs are better suited for lower pressures and loading.

It is very important that the correct pressure range is chosen according to system design pressures for example if a safety relief pressure setting of 11 bar is required do not use a 0.5 to 10 bar rated relief valve as the desired pressure rating is outside the design working pressure parameters, adversely if a low pressure relief valve is required do not use a higher pressure rated valve use the correct RELF or RELT low pressure valve. The reason for this is that the internal spring must be under compression with room to expand or compress, which is why manufacturers will spend a lot of time and money testing flow, pressure control and accuracy against many different spring sizes, lengths, thickness's and materials of construction to find a reliable trustworthy accurately repeatable solution.

Pressure relief valves are available in a direct acting, pressure or servo assisted form, the direct acting relief valve are directly controlled from pressure balance piston, spring and pressure adjustment screw and do not rely on system pressure differentials to operate, and are the preferred choice for most pressure relief valve manufacturers for sizes up to 2" thread or DN150 Flange where pressure differences for small sizes is not commonly guaranteed.

Pressure relief valves are typically now manufactured in 316 stainless steel for the smaller sizes as brass and bronze prices have increased significantly over recent years to a point where there is limited cost savings to be made. General engineering opinion is that when installing a threaded pressure relief valve or a smaller flanged DN15 to DN150 pressure relief valve using a 316 stainless steel valve brings many benefits in terms of corrosion resistance, wear resistance and universal product applications from general purpose water control through to food and chemical processing utilising the same pressure relief valve across all industry sectors. Additional applications include pressure relief solutions for RO water (reverse osmosis) and De-mineralised water and Pure Water and other, aggressive or corrosive media or environments such as Acid and Alkali and most Fluid's and Gas's of similar viscosity.  

Pressure Adjusting Range: 3 to 10 Bar, 7 to 20 Bar

Temperature Range: -15°C to +80°C

Test Pressure: 35 Bar