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What Is The Difference Between A Relief Valve And A Safety Valve?

When it comes to automated safety systems for flammable materials, pressure relief valves and safety valves have a lot in common. However, their differences and purposes are quite different and those differences can become very important.

When handling flammable liquids and gases, safety is critical. It is the legal responsibility of an employer to safely store and justify any storage of a flammable liquid under the Dangerous Substances and Explosive Atmospheres Regulations 2002.

One safety feature that is commonly used is an automatic valve that lets off pressure in a system, taking excess gasses away from the tank and source of danger.

There are two main types of valve, and both operate in similar ways for somewhat different reasons.


Pressure Relief Valve

A pressure relief valve is designed to keep the pressure within a system to a set level and will open gradually in a way that is proportional to the increase in tank pressure.

Generally, there is a threshold of around 10 per cent above the working pressure limit where the valve will gradually open, only fully opening at and above that 10 per cent limit.

These systems are used in compressed air and fluid systems, where it is beneficial for the valve to not fly open whenever there is slight overpressure.


Safety Valves

Safety Valves are designed to prevent a tank failure or critical emergency, by opening and immediately releasing pressure in a system.

They open immediately once they hit the set pressure of the tank, typically three per cent above the working pressure limit, when it will open immediately and channel pressure away from the tank in question, without the need for an operator.