Flowserve 1888 Double-Disc Gate Valve - Manual (Page 14)

14
9.0 MAINTENANCE INSTRUCTIONS (Continued)
9.1.2 Assembly
Assembly of the valves is simply the reverse of disassembly. Prior to reassembly, read the following
special instructions.
(a) All dirt, scale and foreign matter should be removed from inside the valve body and bonnet.
(b) Check the seating surfaces to determine that scratches or minor imperfections do not exist on
the discs or seat rings. If any are evident, lap these surfaces until none are visible.
(Reference Paragraph 9.3.)
(c) Insert the stem (025) into the “T” slot in the upper wedge (069). The lower wedge (071), wedge
spring (269) and discs (004) can now be positioned on the upper wedge. As the stem and disc
pack are lowered into the valve body, they should be contained to reduce the possibility of falling
and becoming damaged.
(d) Once the stem/disc pack assembly is positioned in place, the bonnet (002) can be lowered
into the body neck. Care must be taken in lowering the bonnet onto the stem to prevent
possible scoring.
(e) With the bonnet resting inside the body neck, a new pressure seal gasket (030) can be inserted.
Because tolerances are close and the gasket may cock, it must be inserted with care.
(f) Thread the gasket retainer (033) into the body, tighten to the bottom of the threads and back
out enough to align the packing gland bolts on the valve body. With the gasket retainer in the
proper position, the gland retainer (131) can be lowered over the stem and threaded onto the
bonnet (002). The bonnet will be raised squarely until it is firmly in contact with the pressure
seal gasket.
(g) Note that it is not necessary to torque the gland retainer. The bonnet is truly sealed by pressure.
The only function of the retainer is to hold the bonnet in contact with the gasket until it is
deformed by pressure, locking the joint together and ensuring a tight seal. Since the bonnet is
sealed by pressure, constant cycling will compress the gasket and necessitate tightening of the
gland retainer setscrews.
(h) Once the bonnet is in the proper position, the gland retainer may require backing off to align the
slots for the gland bolts. Once this has been accomplished, the gland retainer setscrews (220)
should be installed and tightened (see Section 11.0 for recommended torque values).
1888-lb. Double-Disc Gate Valve FCD ADENIM0001-00