Explain what is the purpose of blow down in safety valve
BLOW DOWN word is used in boilers also. There are 2 types of blow-down INTERMITTENTBLOW DOWN, CONTINOUS BLOW-DOWN. Basically blow down in boilers means to remove scaling causing elements from BOILER. Similarly BLOW down in safety valve is to remove unwanted pressure.
Steam pressure safety valves are designed to open at a specific set point but once opened the design of the seat keeps the valve open until the pressure falls to a lower set point before it closes. Otherwise, the relief valve would limit the cycle.