GLOBE VALVES OS & Y - FORGED - ISO 15761/API 602/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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lapping operation. The globe stem/disc assembly may be used in the lapping operation. However, due to
its loose design, it is necessary to prevent the disc from rotating on the stem. After lapping it is
recommended that the surface of the seat and disc be checked for proper contact using marking blue.
Coat the seats with marking blue, and tightly screw the disc into seats. Unscrew the disc, and examine to
make sure there is continuous contact between the sealing surfaces of the disc and body seat.
The lapping operation can be performed as follows:
a) Place a small quantity of lapping compound between the seat and disc surface.
b) With the lapping compound in place, between the mating surfaces, the disc should be reciprocally
rotated: the strokes should be light, and the disc should be lifted frequently and turned to a new
position, circularly around the valve body, so the lapping will take place over a new area.
c) Continue lapping until all defects are removed; apply a final finish with a fine lapping compound.
After lapping, it is recommended that the surface of the seat and disc be checked
for proper contact using marking blue. Coat the seats with marking blue, and
tightly screw the disc into the seats. Unscrew the disc, and examine to make sure
there is continuous contact between the sealing surfaces of the disc and body seat.
4.8 VALVE REASSEMBLY & TEST
The procedure to reassemble the valve is as follows:
Re-insert the stem through the stuffing box taking special care to reassemble parts in sequence. If so
equipped, avoid allowing the lantern ring to slide into the stuffing box. If the valve is equipped with a
lantern ring, first insert packing rings into the stuffing box followed by a lantern ring (where applicable).
Next, insert the remaining packing rings into the stuffing box and compress using the gland and flange.
Then, reassemble nuts and tighten.
Note, the stem must slide freely through the stuffing box without applying excessive force. The disc
should be in the half open position.
1. Re-assemble in reverse order of disassembly of Sections 4.3 and 4.5.
2. Bonnet bolts should be tightened in a diagonal pattern increasing torque settings in accordance with
the recommended torque value (see Tables A & B, Appendix A, and Figure 10). Avoid damaging gasket.
Replace the gasket as per Sections 4.3.1 & 4.3.2 if damaged.
3. Test in accordance with API 598.
4. When performing a body test ensure the valve is in the open position but not in backseat position.
Tighten gland packing only just enough to prevent leakage without needing to employ the backseat. In
this way it can be proven the packing is performing it’s task. Over-tightening the packing gland will
increase wear and tear of the packing and can damage the gland, gland bolts or stem. If the valve is
tight to turn with ease, loosen the packing gland slightly. The backseating can also serve to determine
if the valve stem or backseat itself is damaged by slightly loosening the packing gland nuts. Remember,
compressed graphite packing rings will not initially be decompressed when the packing gland is
