Flowserve Vogt Forged Steel Gate - Manual (Page 38)

Flow Control
Vogt Valves
38 Forged Steel Gate, Globe and Check Valves FCD VVENIM2000-02
5.19 Gate Valve Maintenance
Bolted Bonnet Gate Valves
The repair of such valves can be accomplished as follows:
Recommended Spare Parts
1. Bonnet gasket—See Section 1 for part numbers. Listed or un-
listed gaskets are available from Flowserve distribution on short
notice.
2. Packing—See Section 1 for part numbers. Listed or unlisted
gaskets are available from Flowserve distribution on short
notice.
a CAUTION
1. The system pressure shall be totally isolated and
vented from the valve to ensure that the valve is at
zero pressure while being repaired.
2. For small valves valve replacement may be the most
economical way to facilitate repair.
Bonnet Gasket Leaker
1. Remove bonnet.
2. Clean and Inspect gasket recess and gasket surface on the bon-
net. Erosion in the gasket seating area greater than 0.030" deep
will require replacing the valve body and/or bonnet. A machining
allowance of 0.030" is allowed to refurbish the gasket seating
area of the bonnet and body.
a CAUTION: Ensure that any metal removed from the bot-
tom of the depth of the body gasket recess is duplicated
by removing the same amount from the top of the body.
This is required to ensure that the depth of the gasket
recess (0.095–0.100") in the body is maintained.
The bonnet gasket surface can be machined by up to 0.030"
without any additional removal. Body/bonnet gasket surface
metal removal will reduce the thickness of body/bonnet
thickness.
3. Inspect the bonnet bolting to ensure it is proper and bolting is
not damaged or stretched. If bolting is bad it shall be replaced.
Bolting is available from Flowserve distribution on short notice.
4. If the gasket surface is not damaged and/or has been refur-
bished, replace the gasket with a gasket part number noted in
the Recommended Spare Parts Table of Section 1. Gaskets are
available from distribution on short notice.
5. Place the bonnet back on the valve and install the bonnet bolt-
ing. Torque the bonnet bolting in accordance with the torque
requirements of Bonnet Torque Requirements of Section 1.
6. Test the valve and, if acceptable, place valve back in service.
Valve Seat Leaker
1. Remove the bonnet subassembly. Inspect body, seat rings, gate,
and bonnet bolting.
2. If the gate is badly damaged it can be replaced. Since Vogt gate
valves are selectively assembled with matching gates/seat rings
a new gate may not correct a leaking valve. New gates are avail-
able from Flowserve distribution on short notice.
3. If the seat rings are damaged, a loose and leaking valve in ser-
vice cannot be repaired without removal from the line. Special
equipment will be required to replace the seat rings and replace-
ment of the valve is recommended instead of seat replacement.
In the event the user intends to repair the valve, call Flowserve
distribution for seat ring part numbers and availability. Such
parts are available on short notice.
Seal Welded Bonnet Gate Valves
The Vogt valves in this category include valves with threaded
bonnets that, once assembled, are seal welded. They contain no
gaskets. Replacement may be more economical than repair for
these valves.
Bonnet Gasket Leaker
This would be a very unusual event, but if a seal weld leaks, it
should be ground out while the valve is not under pressure, and a
weld repair at the point of leakage shall be performed. See Section 4
for typical weld metal that can be used to weld repair carbon, alloy
and stainless steel valves.
Valve Seat Leaker
Replacement instead of repair is recommended. Seat replacement
will require removal of the valve form the service line. Special
equipment will be required to replace seat rings. Call Flowserve for
seat ring part numbers and availability. Such parts are available on
short notice.
5.20 Globe Valve Maintenance
Bolted Bonnet Globe Valves
The repair of Vogt valves with spiral-wound gasket bonnet joints can
be accomplished as follows:
Recommended Spare Parts
1. Bonnet gasket—See Section 1 for part number. Listed gaskets
are available from Flowserve distribution on short notice.
2. Packing—See Section 1 for part number. Listed packing is avail-
able from Flowserve distribution on short notice.