Following an industry increase in the use of pressure relief valves in applications that required a safety valve, the new guidelines by SAFed were put in place in order to help engineers avoid the occurrence of dangerous overpressure situations. The guidelines focus on areas such as discharge capacity of valves, optimal set pressure, and design temperature of valves.
In addition, the risks of using pressure relief valves instead of safety valves are highlighted. In a pressurized system both safety and pressure relief valves are used as the last safety device. Engineers and specifiers need to be mindful however that the requirements can vary significantly from system to system. Plus increasingly valves must meet the EU’s Pressure Equipment Directive (PED) 2014/68/EU to guarantee safety.
In a pressure relief valve the opening is proportional to increase in the vessel pressure; The opening of the valve is not sudden but gradual if the pressure is increased gradually. For a safety valve the opening is sudden and when the set pressure of the valve is reached, the valve opens completely.
In a pressurized system, both safety valves and pressure relief valves were being used. However, engineers and specifiers need to be aware that valves must meet the EU’s Pressure Equipment Directive (PED) 2014/68/EU in order to guarantee safety and avoid risks. For engineers and installers it is vital to understand when to use the different types of valve. Albion Valves offer a summary showing key characteristics to bear in mind when making a selection.
Safety valves
► Certified valves with WRAS / PED and CE Type Test Approval
► Normal lift – Full lift opening / closing characteristic
► Higher blow-off capacities than pressure relief valves
An example application of a safety valve is the use for a boiler in a commercial building.
Pressure relief valves
► Valve without certification / approval (without safety function according to PED)
► Proportional opening / closing characteristic
► Lower blow-off capacities than safety valves
An example of an application possibility is the use of a pressure relief valve to control the pressure in a manufacturing process.
When PED is applicable, it is mandatory to use safety valves with the appropriate type test approvals. Installation of a valve without this approval means there is no guarantee that the required blow-off at 10% would be reached, which poses a huge safety risk.
Specifiers should look for three important factors when specifying valves in projects where the PED applies:
1. CE Marked in accordance with the EU’s Pressure Equipment Directive (PED)
2014/68/EU
2. Manufactured to a recognized safety valve standard such as EN ISO 4126-1, BS
6759 or API 526
3. Tamperproof to prevent unauthorized adjustment of set pressure.
About Albion Valves
Albion Valves UK have been supplying safety and pressure relief valves for several years and welcome the new guidelines issued by the Safety Assessment Federation (SAFed). The company offers help and advice with the new guidelines and aims to ensure that all engineers are meeting their insurance conditions and not making cheaper and potentially unsuitable options.
For more information, email to: sales@albionvalvesuk.com or visit: www.safed.co.uk.