67.How to set a safety valve? What is Lift and Blow down? How to adjust them?

Raise boiler steam pressure. Near set pressure, lift the stem manually by using rope on the hand pop level. Increase pressure and confirm that the valve is opening at the required set value. Start from the highest set pressure valve. Jack close the low set pressure valves.

Confirm blow down. It shall be between 2 to 5%.

Lift : The amount of  raise  of  stem  while lifting is called  “lift”.

Blow down  : The difference  between set pressure & reseat pressure

                       Expressed  in Æ  percentage of set pressure.

Adjustment :

          Lower ring adj :- To set a clear popping, to close slowly. (To avoid

                                      Simmering & chattering ).

                                      To  reduce simmer,  move the lower ring  upward

                                      ie.  Anticlockwise direction.

                                      1 notch = 42.2ksc.

        Upper ring adj. :-  To adjust blow down  .

                                      To reduce blow down,  move the upper ring upward,

                                       ie., turn anticlockwise.

                                       To increase  blow down , move the ring downward