NIBCO Flanged End Outside Screw and Yoke Cast and Ductile Iron Globe and Angle Valves - Manual (Page 7)

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4.3 LEAKAGE THROUGH THE STUFFING BOX
Leakage through the stuffing box packing may be stopped by tightening the packing
nuts. Excessive tightening may cause difficult operation of the valve and could cause
damage to the stem or packing nut; so do not over tighten. They should be just tight
enough to stop the leak.
If the pack gland follower has run out of travel, isolate, depressurize, and allow valve to
cool and/or decontaminate as required, the valve for repacking or the addition of more
packing. Repacking of valves under pressure is not a recommended practice. This is
dangerous and could result in serious injury even if the valve appears to be back-seated.
Foreign matter may have accumulated on the back seat, or by accident the stem could
be knocked off the back seat position thereby allowing potentially dangerous fluids,
under pressure, to injure maintenance personnel.
First, to remove the old packing, remove the handwheel, packing nuts, pack gland
follower and gland. If the packing is removed, discard and do not try to put it back once it
has been removed. Clean the stem and examine it for damage. Install the new packing
which may either be rope packing or cut rings. Rope packing is sometimes spiral wound
around the stem and pushed into the stuffing box. If rope is used, make sure there is
enough put into the packing chamber so a little bit will stick up over the top. A taper cut
on the top and bottom of the rope will also allow the maximum amount in the chamber.
When the packing is compressed by the gland, it should then be slightly lower than the
top. If rings are used, install one ring at a time with the diagonal cut in each ring being
staggered 90° away from the cut in the ring below. Each ring should be firmly
compressed in the stuffing box after it is placed in position before the next ring is added.
Install the gland bushing and packing nut and tighten down. The packing nut should be
tightened only enough to prevent leakage. Pressurize the valve and check the packing
for leakage. Re-tighten as required.
5.0 MAINTENANCE
5.1 TOOLS AND EQUIPMENT
Standard wrenches and tools are suitable for servicing valves as follows:
A. For removing the bonnet-body nuts and bolts, a full set of 1/2" and 3/4" drive sockets
is normally used. Pipe wrenches on nuts or bolts have a definite crushing action
which will deform them and are not recommended.
B. Standard packing tool can be used and/or a blunt hook is sometimes used to remove
packing rings. A screwdriver to raise the packing gland (if it is in the fully down
position) and generally combination box - open end wrenches are used to tighten the
packing nuts.
C. Punches, hammer, pliers, files, wire brush, putty knife, emery paper, sandpaper,
chalk and other tools generally contained in a good set of mechanics tools will be
needed for things like cleaning up the gasket surfaces, removing pins from stem-
wedge connections, etc.