The procedure for the inspection of a Safety valve fitted on exhaust gas boiler.

Q:- a) Describe the procedure to be adopted for the inspection of a Safety valve fitted on exhaust gas boiler stating with reasons which Parts should receive particularly close attention.

      b) Describe the procedure for the setting of safety valves of Exhaust gas operated auxiliary  boilers.

      c) Explain the action a chief engineer should take after the Setting of safety valves as in (b)

ANSWER :-

a)

1.  When overhauling safety valves care must be taken that parts for each valve are kept separate.
2. When dismantled the spring and the spindle should be hung up and sounded by gently tapping with a hammer. It they do not ring true examine for faults.
3.  The valve spindle should be checked for straightness.
4.  Springs should be checked for distortion and the free length compared against makers recommendation.
5. Check that all drains are clear and the easing gear is free.
6.  Chest and vent pipes should be checked for corrosion and stress cracking.
7. The faces of the seat and valve heads should be checked for damage with compare with the maker’s recommendation. If machining is required then should be carried out following makers instructions with due regards to lip clearances and sitting width etc.

b) Safety valve fitted to boilers and economizers may be adjusted by a fully qualified engineer, holding a First Class certificate of competency, sailing in the rank of Chief engineer. In this case the engineer in question must inform an approved surveyor in writing at the next port of call following the adjustment of valve.

  The following procedure should be followed for exhaust gas safety valve.

1.  Ensure that when the valve was overhauled that it could lift by D/4 when the spring tension was  removed.
2.  Ensure the drain lines are clear.
3.  Ensure that recently calibrated gauge is connected to the economiser. More usually to connect two gauges to ensure accurate setting.
4.  The set pressure of the safety valve would be given to the Chief engineer by class. This pressure should be similar to the previous set pressure of the valve.
5.  Ensure that the main engine is operated above 50 % to ensure that the exhaust gas fired boiler is generating steam to allow the test to continue.
6.  Gag one of the 2 safety valves so that so that one only one valve is able to lift.
7.  Close the Exhaust Gas Boiler steam outlet valve to raise the pressure in the boiler up to the set pressure.
8.  If the valve does not lift at the correct pressure reduce the pressure and adjust the spring tension.
9.  Carry out the above mentioned procedure until valve lifts at correct pressure. Open steam valve fully when safety valve lifts.
10. Measure the distance between the compression ring and valve body.
11. Change the gag over to set the other safety valve using the above mentioned procedure.
12. After both valves are set, release pressure and fit spacer rings beneath compression ring.
13. Replace easing gear and lock top cover to prevent spring adjustment.
14. Record the valves of the safety valve in the engine log book and prepare statement for the Classification society.

c) Once the safety valve has been set the Chief engineer must forward the statement of the  following to the office and Classification Society-

1. Identification number of the vessel .
2. Identification number of the valve adjusted. 
3. Date of adjustment.
4. Opening pressure of the valve .
5. Closing pressure of the valve( blow down Pr).
6. Chief engineers name and Signature.