What is boiler safety valve blowing down period?

1) Blow Down Pressure: Blow down pressure is the difference between safety v/v opening (lifting) and closing pressure.

- More blow down cause of wastage of steam.

-Too less blow down is given an unstable condition. It should be limited 2~5% of the blow off pressure

2) Popping Pressure: Popping pressure is the inlet static pressure that helps to rapid opening of the safety v/v. It is +3~5% of the design pressure or working pressure.
3) Snapping Pressure: Snapping pressure is the v/v spring tension at which the safety v/v is closed.