GLOBE VALVES OS & Y - FORGED - ISO 15761/API 602/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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• If seat & disc required relap see Sections 4.5 & 4.6.
• Then reassemble and test as per Sections 4.3.1 & 4.3.2 below.
4.3.1 Bolted Bonnet Removal & Gasket Replacement
Always replace the bonnet gasket whenever a valve is disassembled. Gasket sealing surface should be
scraped clean (avoid radial marks).
1. Disassemble all cover bolts and nuts.
2. For larger valves (and in the case of higher pressure classes, in smaller sizes), lift up the bonnet using
lifting lugs where provided. For smaller and lower class valves, gently and evenly break the bonnet
seal with a lever if required before lifting the bonnet off (where required with a sling and mechanical
lifting device).
3. Clean gasket surface areas, replace gasket and refit bonnet as detailed below.
4. Reassemble as per Section 4.8.
FIGURE 7
Bolted Bonnet
(Spiral Wound Type)
Bolted Bonnet
(Ring Type Joint)
Welded Bonnet
(Full Penetration Welding)
Extended Bonnet
(Full Penetration Welding)
4.3.2 Pressure Seal Bonnet Removal & Gasket Replacement
In 900 to 2500 class a ‘pressure seal’ bonnet (see example drawing Appendix B) may be specified. The
bonnet bolts or uni-bolt effect a seal on the pressure seal joint which forces the bonnet onto the gasket
which in turn is forced up hard against the outer body. The higher the line pressure, the higher the sealing
force against the gasket, further tightening the seal. The thrust rings are embedded in the body.
Sometimes a ‘breech-lock’ threaded bonnet insert is used instead of a bolt energised bonnet, or a “uni-
nut” system may be used. Refer to as-built drawing. Valves can be specified in conjunction with live
loading bonnet bolt washers that can be tightened to ensure force is applied to the bonnet gasket.
Flexible custom made graphite or metal or combination gaskets may be used. Live loading bonnet bolt
springs may be fitted which can be tightened to ensure a constant force is applied to the bonnet gasket.
See sample drawing Appendix C.
Please refer to as-built drawing as APV has various styles of pressure seal designs.
The procedure to remove a pressure seal bonnet is as follows:
1. After disassembling the packing gland (refer Section 4.2) remove the bonnet bolts (or the threaded
breech-lock bonnet or uni-nut).
2. Remove the segmented gasket.
3. Clean the gasket area and always fit a new gasket before reassembly.
