Flowserve 1878 Double-Disc Gate Valve - Manual (Page 13)

13
9.0 MAINTENANCE INSTRUCTIONS (Continued)
9.2
Replacement of Packing (Reference Figure 1)
If the valve is in service, backseat it. If the valve is not backseated be sure that line
is depressurized.
(Refer to Figure 1 for referenced part designations.)
(a) Remove the two (2) Gland Stud Nuts (234) and raise the Gland Flange (133)
allowing the Gland Bolts (210) to be removed.
(b) Lift the Gland Flange (133) upward and away from the stuffing box area.
(c) Use a packing hook or similar device to remove the old packing.
(d) Install the Packing (110, 112) one ring at a time - carefully placing the joint of
each ring approximately 180
° from the preceding piece to prevent a leakage
path. It might be necessary to slightly flatten each packing ring prior to
installation to allow easy insertion within the stuffing box. Do not use a
pointed instrument to push the rings into position. The Gland Flange (133)
or a Packing Iron (See Figure 3) should be used to seat the packing in
position once a ring has been slipped within the box.
(e) Upon completely filling the stuffing box, replace the nuts and bolts and very
carefully draw the packing to assure that the Gland Flange (133) is even and
that the bore of the Gland Flange is concentric with the valve stem. (If the
Gland Flange (133) is drawn unevenly, scoring of the Stem (025) may result;
or the Gland Flange might be tilted which could cause binding.)
(f) Check the packing periodically (6-month intervals) replacing as needed.
9.3
Lapping Procedure
After the valve has been disassembled, a visual inspection of the seating surfaces of
the Discs (004) and Seat Rings (013) can be made to determine if lapping is
necessary to remove any minor scratches on these parts prior to assembling the
valve. The following procedure should be followed:
(a) The disc should be lapped on a flat grooved lapping plate, or if available, a
lapping machine may be used. A "medium" grade lapping compound should
be used for the first and successive applications and a "fine" grade
compound similar to "Clover A Grit No. 280" should be used for the final
lapping process.
(b) If it is necessary to lap the face of the seat ring, a standard lapping plate can
be used of approximately the same diameter as the disc.