Special Features of Valve Lid and Seat:

• The seat's design deflects escaping steam towards the valve lid's lip, boosting the valve's lift. This increases the efficiency of steam release.
• The pressure of escaping steam acting on a piston provides extra lift to the valve. This helps in a faster, more complete opening.
• A loose pin secures the valve lid, allowing for thermal expansion without stress.

Overhauling the Boiler Safety Valve:

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