Power plant and calculations: Clear steps for Boiler Safety valves major overhauling

Boiler Safety valve major overhauling steps

Cleaning of safety valve
Complete dismantling of safety valve.
Cleaning, polishing & buffing of parts.
Thorough inspection of all parts.
Seat & disc lapping
Spindle run out (bend) checking
Spring checking for any abnormalities like crack, bend, reduced tension etc
Lapping of both disc & seat.
Inspection of upper & lower ring teeth for damage/crac
Measurement & re-assembly.
Inspection of discharge pipe connection. If there is telescopic discharge pipe, then ensure a gap of minimum 10 mm for thermal expansion.

ASSEMBLY STEPS.

1-After seat & disc lapping, place lower nozzle ring on seat & level both the faces

Questions & Answers on Safety valves

2-After leveling, turn the lower ring by 3 notches in clockwise direction.

For example if Safety valve’s operating pressure is 117 kg/cm2, then 117 kg/cm2/42.4 kg/cm2 = 2.75 Appx. 3 Nos i.e 42.4 kg/cm2 for every notch (For more details, refer manufacturing data)

Then lock the lower ring by inserting lower set screw

3- Take measurement from seat top to guide (89-90mm)

4-Then measure the length of upper ring (it should be same as seat top to body top) & place it into the body

5-Fit disc to spindle then place disc with disc holder & spindle into the body & lock it by set screw

6-Put a body on spindle & lock the spindle by split pins & adjust the lift ,to increase the lift , rotate the lift stop collar clockwise & to decrease the lift, rotate the collar in anticlockwise direction. For every one full rotation, 1.58 mm lift can be adjusted.