Leakage around the valve stuffing box is usually an indication that the stuffing must be adjusted or replaced. This leakage does not occur when the valve is completely opened or closed. Therefore, an absence of leakage is not necessarily an indication that the valve is functioning normally.
Once you have detected leakage, check first to determine whether or not adjusting the packing will stop it. If it is a bolted bonnet valve, turn the packing gland nuts (or gland stud nuts) clockwise alternately with no more than 1?4 turn on each until leakage stops. If you are dealing with a screwed and union bonnet valve, turn the packing nut clockwise until the leakage stops. If the leakage will not respond to adjustment, the packing must be replaced.
The procedure for replacing the packing in most valves may be summarized as follows:
1. Remove the handwheel nut and the handwheel.
2. Remove the packing nut.
3. Slip the packing gland off of the stem.
4. Replace the packing.
5. Reassemble in reverse order.
The procedure used with bolted bonnet outside screw and yoke valves is a little more complicated. On Y valves of this type, it is necessary to remove the gland flange and gland follower before replacing the packing. On globe and angle valves, the stud nuts and upper valve assembly must be removed.
Because of their design and construction, the problem of stuffingbox leakage does not occur with check valves.