Inspection and setting of safety valve of an exhaust gas boiler

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We all know the procedure to be followed for a boiler survey. Also we know the safety parts associated with any boiler survey. So, lets see which all parts should receive close attention while inspecting a safety valve:

  1. Check condition of internal parts of valve for sign of corrosion,galling and wear.
  2. Check for pitting, cracking, resiliency and condition of spring
  3. Check spindle for straightness and adjusting ring threads for freedom of movement.
  4. Check the discharge and drain piping, it should be well clear.
  5. Check dampers to ensure that linkages are secured and well greased.
  6. The faxes of seats and valve heads should be checked for damage with maker's recommendation.
Now safety valve of an exhaust boiler can be set only out at sea when main engine is running. So, this can be set by only a class 1 holder person serving as chief engineer on board the vessel. Procedure for setting the valve is as follows:-
  1. Ensure that overhauled valve can lift D/4 when spring tension is removed.
  2. Take necessary safety precaution and arrange gagging tool and recently calibrated master gauge.
  3. The set pressure of the safety valve will be given by class and it will be same as previous set pressure.
  4. Main engine should be running minimum at 50% MCR so that sufficient exhaust gas is produced to raise the exhaust boiler pressure.
  5. Gag one of the safety valve so that only one valve is able to lift.
  6. Slowly raise the boiler pressure and blow off the safety valve manually few times for thermal expansion and to reduce the thermal stress on the valves.
  7. Raise the steam pressure to the value at which the safety valve has to lift. If valve does not lift reduce the steam pressure and then adjust the spring tension.
  8. Carry out above procedure until valve lifts at correct pressure.
  9. Measure distance between compression ring and valve body.
  10. Same way set the other valve.
Once Chief engineer sets the safety valve of exhaust boiler, he has to prepare a statement for the classification society. The statement should contain following:-
  1. Identification number of vessel and valve adjusted.
  2. date of adjustment.
  3. Opening pressure of the valve
  4. Closing pressure of valve
  5. Name and signature of chief engineer.

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