The method of setting the safety valves of an exhaust gas boiler at sea:

The safety valve setting process involves two key adjustments:

1. Adjustment of Blowing-Off Pressure
2. Adjustment of Blowdown Pressure

Steps:

• Increase the steam pressure to about 20% below the intended blowing-off pressure.
• Ensure the main steam stop valve remains closed to prevent steam from entering other systems.
• A calibrated pressure gauge should be installed to ensure accurate readings.
• Have gagging tools handy for use during the adjustment.
• The person adjusting the valve should wear proper PPE to ensure safety.
• Check the operation of the safety valve by using the easing gear, which ensures all valve parts are near working temperature when the valve lifts.
• Disassemble the easing gear, including the cap nut and cotter pin.
• Gag the other safety valve to isolate it from the system.

Initial Adjustment:

• Check the position of the compression screw and loosen it slightly to remove the compression ring.
• Tighten the screw by one or two turns to increase the spring load.

Blow-Off Pressure Setting:

• Gradually raise the steam pressure. As the blow-off pressure approaches, slowly unscrew the adjusting screw until a hissing sound is heard, followed by the valve lifting.
• Record this pressure, which is the approximate blow-off pressure.

Blowdown Pressure:

• Reduce the boiler firing rate to a minimum. When the valve reseats, it will do so at a pressure lower than the blow-off pressure. This is the approximate blowdown pressure.
• The blowdown pressure can be fine-tuned by adjusting the blowdown ring, usually 5% lower than the maximum working pressure.

Final Adjustments:

• Recheck the blow-off pressure by increasing the firing rate to ensure accuracy. Make adjustments as needed.
• Once set, reinstall the compression ring and verify that it is properly secured between the compression screw and neck bush on the valve top cover.
• Repeat the same procedure to set the second safety valve.

Easing Gear Check:

• After both valves are set, reconnect the easing gear and ensure it operates safely.

• The safety valve should lift at a pressure not exceeding the maximum permissible working pressure by more than 3%.
• The accumulation pressure (maximum pressure reached during full discharge) should not exceed the maximum permissible working pressure by more than 10%.
• The blowdown should typically be between 2% and 5% below the set pressure.

• Prepare a detailed report including:
  • Blow-off pressure
  • Blowdown pressure
  • Width of the compression ring
  • Date and signature of the person responsible for the adjustments.
• Obtain the signature of a surveyor to validate the safety valve setting.
• Send a copy of the report to the office.
• Keep the original report in the ship’s records for future reference.