SALIENT FEATURES
Safety valves are very critical components of boiler assembly. They are important in maintaining safety of the boiler when the pressure in the boiler rise beyond the operating pressure due to unforeseen circumstances. In addition, they are also used in thermic fluid systems and other pressurized fluid lines for the same reason to protect the pressurized system from the hazards of uncontrolled pressure damage.
Functioning of A Safety Valve :As stated in the name, the pressure valve is designed to open at a set pressure provided by the OEM. The valve is set against the seat of the safety valve using a compression force of the spring. As the pressure rises in the inlet nozzle of the safety valve, a counter force starts building up against the compression force of the spring. The spring is design in such a way that it will compress and thereby open the valve as soon as the pressure in the inlet nozzle exceeds the set pressure stated by the OEM. Safety valve will discharge the fluid through its outlet flange until the pressure in the inlet nozzle reduces below the set pressure. At this point, the force built up in the compressed spring will come into action and shut the valve back.
Sizing of A Safety Valve : Safety valve sizing is dependent on four important parameters
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C = Constant of discharge as approved by IBR
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Setpressure of the boiler operation. Setpressure is typically provided in terms of Bar/ Kg/cm^2/PSI
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Discharge of the boiler. Discharge is provided in Kg/hr / Tonnes/Hr
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Temperature of the fluid in centigrade/Fahrenheit
There are two categories of safety valves. :
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High Lift Safety Valves
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Full Lift Safety Valves
High Lift Safety Valves have a lower discharge constant versus Full Lift Safety Valve. Hence for the same discharge of the boilers, A higher size of High Lift Valve is required versus Full Lift. Selection of High lift versus Full Lift mainly depends upon the approved IBR drawing of the boiler OEM.Normally, each boiler design requires a set of Two Safety Valves fitted on top. Here is a general range of MH Valves Manufactured safety valve for a boiler discharge operating at 10.5 kg/cm^2
