NIBCO Fire Protection Gate Valves - Manual (Page 7)

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7
Repacking of valves under pressure is not a recommended practice. Prior to proceeding
to change packing, it will be necessary to shut down the piping system, remove pressure
and drain, and if necessary, allow cooling and/or decontaminating before working on the
valve.
For F-609 and M-609 non-rising stem metal seated gate valves, remove the square
operating nut by unscrewing the nut on the top end of the stem, also unscrew the two
nuts that hold the indicator-post flange in place; this will allow the indicator-post flange to
be lifted or slipped off of the stem. Find the two O-ring seals on the inside of the stem-
hole bore of the indicator-post flange hub and replace damaged or worn O-rings.
For rising-stem, metal-seated gate valves it is not necessary to remove the handwheel.
Remove the packing nuts and bolts, slide the pack gland follower, pack gland up out of
the way and keep out of the way with tape or some other convenient temporary method.
If the packing is removed, discard and do not try to put it back once it has been
removed. Reusing old packing is a gamble not worth taking. Clean the stem and
examine it for damage. Install the new packing, which my 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. 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 packing gland and pack gland follower, packing
nuts, and tighten down. The packing nut should be tightened only enough to prevent
leakage. Pressurize the valve and check the packing for leakage. Retighten as required.
For resilient-seated gate valves, follow the above and replace the O-ring or split flat
rubber seals.
5.0 MAINTENANCE
5.1 TOOLS AND EQUIPMENT
Standard wrenches (adjustable, open-end, box-end, Allen) and other standard tools are
suitable for servicing valves as follows:
A. For removing bonnet-body nuts and bolts full set of 1/2” and 3/4” drive sockets is
normally used. Pipe wrenches used on nuts or bolts have a definite crushing action
which will deform them and is not recommended.
B. A 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, 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.