Safety:

• Carry out a Toolbox meeting, Risk assessment and Permit to work.
• Ensure that the internal pressure of the boiler is fully relieved before attempting to remove the safety valve. Wear appropriate personal protective equipment (PPE), including safety glasses, to protect against residual fluid splashes.

Disassembly Steps:

• Remove the seal and pull out the split pin.
• Detach the fork lever.
• Loosen the set screw and remove the cap.
• Remove the spindle lock nut and adjusting screws from the spring cover (make a mark on the position of the adjusting screw and spring cover for easy reassembly).
• Take off the spring cover.
• Remove the nut connecting the yoke with the body, then lift the block composed of the yoke, upper spring, and lower spring carrier along with the spring.
• Pull out the spindle.
• Remove the disc.
• Loosen the screw and remove the valve seat.

Checks:

• Inspect the valve seat and disc for damage; lap if necessary.
• Check the sliding surface of the floating piston for dirt and foreign materials, cleaning thoroughly.
• Assess the condition of the spindle for trueness.
• Inspect the body for rust and corrosion.
• Examine the spring for cracks and measure its free length.
• Verify the working of the easing gear.
• Ensure the drain line is clear.
• Conduct non-destructive testing of components as needed.
• Check the condition of the blowdown ring and the compression ring neck bush.

Clearances to be measured:

• Measure the clearance between the valve lip and the seat lip.
• Clearances between spindle and cap nut
• Measure the clearance between the cotter pin and the groove in the spindle.
• Check the clearances between the floating piston and the spindle.
• Check the lift after assembly. It should be more than D/16 for high lift safety valve

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.

• Measure the distance between the lower face of the compression nut and the upper face of the column cover plate of the yoke.
• Measure the size of the compression ring for future reference.
• Reassemble the easing gear and confirm that it operates correctly.
• Secure the valve settings by placing a lock to prevent any unauthorised tampering with the settings.
• 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.