GLOBE VALVES OS & Y - FORGED - ISO 15761/API 602/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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Only an experienced valve repair professional should attempt repairs to pressure
seal bonnet valves. There are different designs of pressure seal bonnet: - locknut
type (breech lock), bonnet take-up type (bolted yoke arm) and the bolted style,
hence, refer to as-built drawings. See Appendix C for for example.
4.4 BONNET REASSEMBLY
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. 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. Finally, install
the bonnet gasket making sure it is not damaged. The gasket should be replaced if there is any question
as to its performance (refer to Sections 4.3.1 & 4.3.2).
Raise the bonnet, making sure the stem is in the half open position, then connect disc to stem. Lower
bonnet on to the valve body making sure that the disc fits exactly into body guides and the bonnet is
properly seated. Align holes and tighten bonnet nuts taking care that excessive force is not used, to avoid
damaging the gasket. Hydrostatically test the valve to ensure that there is no leakage.
4.5 DISASSEMBLY OF YOKE NUT
When necessary use the following procedure for disassembling and replacing yoke nut:
a) Direct hand operated valves (hand wheel)
• Remove set screw;
• Unscrew hand wheel nut;
• Remove hand wheel;
• Unscrew yoke nut retaining nut, removing spot welds if necessary.
Reverse the procedure for reassembly.
b) Bevel gear operated valves
• To remove the bevel gear from the valve, unscrew nuts and turn the hand wheel in the open
direction indicated by the arrow until the drive nuts are disengaged from the stem.
• To check the condition of the drive nut or bearing, unscrew the retainer ring and remove drive nut
and bearing. If damaged, a new drive nut or bearing is necessary.
4.6 DISC AND SEATS
An indication of valve leakage is a pressure loss in the high pressure line side after a valve has been
properly closed. In the case of hot water or steam lines, note whether the downstream pipe remains hot
beyond the usual length of time. This type of leak may be the result of a distorted seat caused by
improper welding of the valve into the pipeline or seating damage caused by foreign particle matter or
by stress relieving temperatures that may have been used during installation.
