SAFETY VALVES are an arrangement or mechanism to release a substance from the concerned system in the event of pressure or temperature exceeding a particular preset limit. The systems in the context may be boilers, steam boilers, pressure vessels or other related systems. As per the mechanical arrangement, the safety valve get fitted into the bigger picture (part of the bigger arrangement) called as PSV or PRV that is pressure safety or pressure relief valves.

This type of safety mechanism was largely implemented to counter the problem of accidental explosion of steam boilers. Initiated in the working of a steam digester, there were many methodologies which were then accommodated during the phase of industrial revolution. And since then this safety mechanism has come a long way and now accommodates various other aspects.

These aspects like applications, performance criteria, ranges, nation based standards (countries like United States, European Union, Japan, South Korea provide different standards) etc. manage to differentiate or categorize this safety valve segment. So, there can be many different ways in which these safety valves get differentiated but a common range of bifurcation is as follows: ASME valves Lift safety valve Flow controlled valve Balanced valve Power operated valve Full lift solid line valve Direct safety loaded valves Master valve

The American Society of Mechanical Engineers (ASME) I tap is a type of safety valve which opens with respect to 3 percent and 4 percent of pressure (ASME code for pressure vessel applications) while ASME VIII valve opens at 10 percent over pressure and closes at 7 percent. Lift safety valves get further classified as low-lift SAFETY VALVES and full lift safety valves. The flow control valves regulate the pressure or flow of a fluid whereas a balanced valve is used to minimize the effects induced by pressure on operating characteristics of the valve in context.

A power operated valve is a type of pressure relief valve is which an external power source is also used to relieve the pressure. A proportional-relief valve gets opened in a relatively stable manner as compared to increasing pressure. There are 2 types of direct-loaded safety valves, first being safety valve diaphragms and second: bellows valves. Safety valve diaphragms are valves which spring for the protection of effects of the liquid membrane while bellows valves provide an arrangement where the parts of rotating elements and sources get protected from the effects of the liquid via bellows.