any flash files explaining valve operation maintenance will be very much helpful
Hydraulic Pressure Relief Valve Animation
A pressure relief valve or safety valve is used in pipe lines or any other pressure vessel (pressure cooker for eg) where pressure exeeding the strength of the metal of the container or the pipe has to b avoided to prevent failure of the metal or possible explosion.in a pressure relief valve the inlet of the valve is connected to the pressure area where as the outlet is connected to atmosphere.the valve lid is held against the pressure via a compression spring.when the pressure in the pipeline or pressure vessel exceeds the spring pressure the valve lid opens and the pressure is relieved.
A pressure regulator is simply a device designed to maintain a certain pressure on a system or piece of equipment. A safety relief valve is a device designed to prevent the over pressure of a system or piece of equipment. The intent is to prevent a failure, rupture or explosion. The basis for the design of a pressure regulator is governed by good engineering practice while a safety relief valve in most cases is also governed by specific codes, regulations and laws. In the United States local boiler and pressure vessel regulations are the most common governing agency along with the ASME/ANSI Codes.
A pressure reducing valve brings the pressure down to some constant level that is safe for the downstream equipment (it is something that is constantly working). A safety valve is something that only opens when the pressure exceeds a safe level. On all large boilers you will find two safety valves (two in case one of them fails to open). These will open up as soon as the boilers pressure rises above the boilers maximum permissible pressure (protection against the boiler exploding). A pressure reducing valve will be fitted just before a cooker that will bring the steam pressure down to a level that is safe for the cooker to use. It's normally a good idea to have a relief valve downstream of a pressure reducing valve (a relief valve is almost like a safety valve). If the pressure reducing valve fails, the relief valve will open up and provide a outlet for the steam so that the cooker doesn't get damaged.
