GLOBE VALVES OS & Y - FORGED - ISO 15761/API 602/B16.34
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
11
APV does not make any recommendations in regards to the actual PWHT details of
temperature and time. This work is not within the scope of APV. APV recommends
that all applicable “Piping Code” requirements be considered.
For alloy steel valves or when welding specification or service conditions require field PWHT, the valve
may be order with pipe nipples already welded and heat treated in the factory before valve assembly.
The specified PWHT can then be performed in line without affecting the valve.
1.4 POST-INSTALLATION PROCEDURES
After installation, the line should be cleaned by flushing to remove any foreign material. When caustics
are to be used to flush the line, additional flushing with clean water is required. The valve should be
opened and closed after installation to ensure proper operating function.
With the line pressurised, check the valve end connections, body to bonnet/cover joints and stem packing
area for leaks. The packing may have to be tightened to stop packing leakage.
2 . 0 O P E R A T I O N
Forged globe valves should not be used to throttle to openings less than 20% or else flow induced
vibration/venturi effect will damage seat and disc. Because of the body’s labyrinth design, the globe
valve causes a larger pressure drop than a gate valve. Because of this, the globe valve is an excellent
device for regulation of flow in the moderate to full flow range.
Globe valves should not be left in the fully backseated position under normal
operating conditions. The packing may dry out under these conditions and leak as
the valve is closed. However, depending on media, size, class and valve age many
operators choose to leave the valve fully backseated at all times. Even when doing
so there will still be usually some minor leakage past the back seat.
A cool valve may leak through the gland when opened to hot fluid. Wait before tightening the packing as
the problem may go away.
