Pressure Safety Valve and Pressure Relief Valve are commonly used terms in process industries. Both terms are used interchangeably in the industries. Both are associated with devices / equipments, personnel, property, environment damage & safety.

Relief valves and safety valves are the two principle safety devices designed to prevent overpressure conditions in process industries.

One can say relief valve or pressure relief valve is a type of  safety valve used to control or limit the pressure in a system; otherwise the buildup of over pressure may create a process upset, instrument or equipment failure,  fire or can causes personnel damage. 

Pressure Relief Valve.

 

The relief valve is designed or set to open at a defined pressure so that if the excess pressure is getting buildup in the process vessel/equipment(Such as : boiler, pressure vessel, pressure cooker etc) then the relief valve is forced to open just by lifting of the lever and a portion of the fluid is diverted through the auxiliary route. The diverted fluid (liquid, gas or liquid–gas mixture) is usually routed through a piping system known as a flare header or relief header.

Pressure relief valve are getting mounted excatly in a vertical position. Any position other than vertical may hamper the performance of PRV significantly.

The opening of the relief valve not occurs in a sudden; it opens gradually as the pressure increases gradually.

Pressure Safety Valve

A safety valve is a valve that acts like fail-safe device. Safety valves are designed and manufactured by considering that it will be mounted exact vertically. Horizontal mounting/Non Vertical mounting can have many adverse effects.

Generally used to handle compressible fluids(gas, vapour or steam).

The safety valves opens in a sudden as the pressure exceed beyond preset limit. This valve opening is almost 100%. The device is so designed so that the safety valve trips automatically when the given pressure is attained.

Vacuum type safety valve is getting used in tanks to avoid collapsing when it is getting emptied. Application of this valve where CIP or SIP is done of the vessels.

In a simple terms, a relief valve is a device designed to control the pressure in a vessel or system to a specific set level.

where as, A safety valve,  is a device used to let go excess pressure from a vessel or equipment when the pressure crosses a certain predetermined limit. It simply allows liquids or gases to escape if the pressure gets too high to prevent any damage.

Relief Valve Vs Safety Valve Comparison Chart

Conclusion :

Both relief valves and safety valves are high-performance pressure-sensitive safety devices so designed to control or limit the pressure inside the system or vessel by releasing the excessive pressure from the auxiliary passage out of the system.

ImageSource : Wikipedia; Difference Between

Article Source : Wikipedia; Difference Between