- 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.
8-Then fit upper washer & yoke assy.
thrust bearing & spindle lock nuts
Basic concepts of safety valves
BLOWDOWN
ADJUSTMENT
To increase the blow down: Lower the upper
ring by 7 notches for 1Kg/cm2
To decrease the blow down: Raise the upper
ring by 7 notches/1 Kg/cm2
To reduce shimmering: Raise the lower ring
by one notch up, if not adjusted again rise one notch up. This is allowable
till ring levels seat top.
