Flowserve V-377 R4 Edward Valves - Manual (Page 32)

32
Flow Control Division
Edward Valves
6. Partially back off the remaining bon-
net stud nuts. Raise the yoke, and
insert uniform shims in at least three
places between the yoke flange and
the body.
7. Raise the pressure-seal gasket by
tightening the bonnet stud nuts uni-
formly a fraction of a turn at a time
using a star pattern. It is possible to
damage the valve parts by cocking
the bonnet, so uniform turning of
these nuts is very important. Note
that it will only be possible to raise
the gasket a distance equal to the
thickness of the shims used in step 6.
When this point is reached, the nuts
should be backed off again, more
shims added, and the process repeat-
ed until the gasket comes free of the
body.
8. Use a chain hoist in line with the
stem to lift the stem yoke bonnet
assembly out of the body. During this
process, mark the body, yoke, bon-
net, and pressure-seal gasket at cor-
responding points (other than sealing
surfaces) so that their relative position
can be duplicated in reassembly. In
laying the parts aside for inspection,
it is imperative that they be placed
carefully on a bed of rags or other
soft material to avoid marring any
machined surface, particularly any
seating and sealing surfaces.
9. Unscrew the stem from the yoke
bushing.
10. Remove the bonnet stud nuts;
separate the yoke and bonnet.
11. On stop valves, the disk and disk-nut
assembly is attached to the stem. On
stop-check (non-return) valves, the
piston-disk assembly is not attached
to the stem and must be removed
separately. See step 12.
12. Screw 1/2”-13 bolts (3/8”-16 on
sizes 5” and smaller) into the thread-
ed bosses or nuts provided in the pis-
ton. The piston can now be lifted
from the valve. Occasionally a vacu-
um may be formed by the cooling
fluid in the pipe line below the valve.
Until relieved, this vacuum will pre-
vent removal of the piston. Since the
piston must be removed through the
pressure-seal area of the bonnet
bore, use caution to avoid marring
the scaling surface in any way.
13. The bonnet end opening should be
kept covered whenever possible.
Type I Pressure-Seal Bonnets
Piston-Lift Check Valves
See Illustration No. 21 on page 29.
Piston-lift check valves are constructed with
valve bodies similar to the corresponding
stop or stop-check (non-return type) valves.
Assembly is simplified by the absence of a
yoke and stem.
Note: Care must be taken in removing the
cover retainer nuts, in case pressure should
be trapped in the body (down-stream pip-
ing). Check to make certain all down-
stream pressure is relieved. Once the cover
retainer nuts are completely removed, the
cover/cover retainer assembly is held only
by the friction of the pressure-seal gasket
again the body bore. Trapped pressure
could cause these parts to be blown out
with considerable force. Therefore, care
must be taken to relieve all pressure, and
break the cover and pressure-seal gasket
loose before the cover retainer nuts are
completely removed.
1. Carefully remove the cover retainer
nuts, observing the above caution.
2. Remove half of the cover stud nuts,
alternating to leave those remaining
evenly spaced.
3. Partially back off the remaining bon-
net stud nuts or cap screws. Raise the
cover retainer and insert uniform
shims in at least three places between
the cover retainer and body.
4. Raise the pressure-seal gasket by
tightening the bonnet stud nuts or cap
screws uniformly, a fraction of a turn
at a time using a star pattern. It is
possible to damage the valve parts
by cocking the cover, so uniform turn-
ing is very important. Note that it will
only be possible to raise the gasket a
distance equal to the thickness of the
shims used in step 3. When this point
is reached, the nuts or cap screws
should be backed off again, more
shims added, and the process repeat-
ed until the gasket comes free of the
body.
5. Lift the cover/cover retainer assembly
out of the valve. During this process,
mark the body, cover/cover retainer,
and pressure-seal gasket at corre-
sponding points (but not on sealing
surfaces) for reference and reassem-
bly.
Disassembly Procedures for Bonnet Types
(continued)