Masoneilan 10000 Series Globe Valve Instruction Manual | 4
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replacement or re-machining of one or both parts. When lapping
new plug and seat ring, begin with medium compound and finish
with fine.
Before lapping plug and stem must be true (see pinning operation,
section 6.4).
Note: Seat repair in a double seated valve is critical. In a new
valve the distance between the upper and lower seat ring seats is
established in manufacturing and only lapping is required to make
both parts close simultaneously. In the field, it is best to lap the
seats first. If one of the seats is damaged beyond what is repairable
by lapping, care must be taken to maintain the original distance
between the seats on both the plug and seat rings. Therefore, when
machining one seat of the plug or one seat ring the other must be
machined in exactly the same way.
A. Clean body gasket surface areas.
B. When the seats have been removed, ensure that the sealing
surfaces in the body bridge and the threads are thoroughly
cleaned.
Note: A lubricant such as Chesterton 725 or a sealant compatible
with the process should be applied sparingly, to the seat ring
threads and sealing shoulder.
C. Install and tighten seat rings using fabricated wrench used for
removal. (See Figure 3).
Do not over tighten. Do not strike seat ring lugs, this could distort
the seat ring resulting in unwarranted seat leakage.
D. Install bottom flange (10), ensuring bottom bushing (14) is in
place and secure to the body using body stud nuts (12) spaced
equally apart. Fasten the bottom flange to the body using only
slight pressure and tighten evenly.
Do not tighten nuts to torque specifications at this time. The
bottom flange is used temporarily for guiding purposes.
E. Apply lapping compound at several spots equally spaced around
the seating areas of the plug.
F. Insert the stem and plug assembly carefully into the body until
it is seated.
G. Place bonnet (6) on the body and using body stud nuts (12),
spaced equally apart, fasten to the body using only slight
pressure and tighten evenly.
Do not tighten nuts to torque specifications at this time. The
bonnet is used temporarily for guiding purposes.
H. Insert two or three pieces of packing (17) into the packing box to
assist in guiding the stem and plug during lapping.
I. Screw a drilled and tapped rod with a tee handle onto the plug
stem and secure with a lock nut. (See Figure 5).
Note: As an alternative, drill a hole through a flat piece of steel
and fasten to the plug stem using two lock nuts.
Figure 5
J. Apply a slight pressure on the stem, rotating the stem in short
oscillating strokes eight to ten times.
Note: The plug should be lifted and turned 90˚ before repeating
step 10. This intermittent lifting is required to keep the plug and
seat ring concentric during lapping. After completion of the
lapping operation, remove body stud nuts (12) from the bonnet
(6) and bottom flange (10).
K. Remove bonnet (6) and bottom flange (10).
L. The seat rings, plug and internal components of the valve must be
cleaned of all lapping compound in preparation for reassembly.
6.4 Plug Stem Pinning
Valve plug and stem assemblies are normally furnished as a
complete assembly in which case the installation involves no
problem. It is only necessary to lap the plug and seat ring and
assemble the valve. If it is necessary to replace the plug it is
recommended that a new stem be used. If the old stem must be
used, it is necessary to determine if the stem will be long enough
since the stem will require cutting. If the stem does not engage the
actuator stem by a minimum of one stem diameter, the old stem
should not be used. If it does not engage a minimum of one stem
diameter, proceed as follows.
Note: While pinning is being performed, care must be taken not to
damage the seating surface and plug guides.
A. Using a drift punch, drive out the old pin (8).
Note: If it is necessary to drill out the pin, a drill somewhat
smaller than the pin should be used and the remainder of the
pin driven out.
B. Unscrew the plug from the stem (counter clock-wise).
Figure 6