Flowserve Cast Globe Valves - Manual (Page 30)

Globe Valves FCD ADENIM0011-00
30
7.0 ASSEMBLY
Before starting-the reassembly of the valve, all parts should be thoroughly cleaned and inspected. All foreign material should
be removed from any area of the valve. However, there are certain critical areas that must be free of dirt, weld spatter, filing,
etc. These include the following:
1. Disc and seat sealing surfaces
2. Bonnet 00 fen pressure seal valves)
3. Body neck 19 (on pressure seal valves)
4. Gasket tongue (on flanged bonnets)
5. Gasket groove (on flanged bodies)
6. Bonnet studs- and nuts
7, Stem (all)
8. Stuffing box-(ID)
9. Gland (all)
10. Pressure- seat gasket
These ten areas must also be free of any nicks, scratches, gouges, etc. Any damage in these areas must be repaired. Any
questions about the acceptability of any surface condition should be discussed with a service engineer prior to using the part.
7.1 Flanged Bonnet Valves
7.1.1 Disc-Stem Assembly
The first step in the assembly process is to check the disc pack to seat ring clearance and adjust if
necessary.
1. Prior to attaching the disc (004) to the skirt (005), the stem retainers (028) must be installed. The simplest
way to accomplish this is slide the skirt up over the lower end of the stem until the retainer slot in the stem is
exposed. The stem retainer halves can be inserted into the slot. Lowering the skirt on the stem will capture
the ring and hold it in place.
2. The skirt/stem assembly can now be placed over the disc and threaded into it either by rotating the disc
or the skirt. With the skirt fully threaded into the disc, there should still be some flexibility between the disc
and the stem. If the connection is rigid, the skirt should be backed out a quarter turn to provide some
freedom.
3. After proper positioning, the skirt should be tack welded to the disc in three places 120 degrees apart.
7.1.2 Bonnet
Prior to lowering the bonnet (002) into position, a new gasket should be placed in the gasket groove on the
body flange. Carefully insert the stem into the backseat bushing in the bonnet and lower it into position on
the body. In lowering the bonnet be careful that neither the backseat nor the stem are scratched or gouged.
Damage to either of these surfaces can impair their sealing ability. If orientation of the actuator is important,
the bonnet should be rotated to its proper position prior to lowering it onto the gasket. With the bonnet in
place, the studs (200) and nuts (230) can be installed. Prior to installation the studs and nuts should be
cleaned and thoroughly lubricated with a high quality lubricant. Any nuts or studs with damaged threads
should be replaced. It is very important that the body-bonnet bolting be torqued to specific value in
accordance with a specific procedure. The torque valves are shown in Table 1 for various diameter studs.
The nuts should be tightened evenly using a criss-cross pattern similar to the one shown in Fig. 22. Tighten
all of the nuts to 1/3 of the recommended valve initially. Then repeat the sequence raising the torque to 2/3
of the full torque. Finally, torque all the nuts to the recommended value following the criss-cross pattern. It is
essential that the flange faces remain parallel and all the bolting has uniform tension. Failure to achieve
this may cause gasket weepage when the joint is subjected to operating pressures and temperatures.