LUBRICATED PLUG VALVES - SAPM/SAPL
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
10
2.2 WRENCH OPERATION
The wrench has a ‘square’ style head, and can be fitted to the valve in a number of positions to suit
operation. The wrench must always be secured to the plug stem by tightening the retaining screw onto
the plug stem. The are positive stops provided on the plug stem and gland to ensure correct operation of
the valve.
During operation of the valve the use of excessive side loading on the wrench should be avoided. APV
provide wrenches that are sized so that the force to operate the valve should be 15 NM maximum at the
end of the wrench.
2.3 GEARBOX OPERATION
APV gearboxes have a visible arrow type position indicator on top of the gear housing. ‘OPEN’ and ‘SHUT’
positions are cast on top of the gear housing. The position indicator arrow points to these when in the
fully opened and fully closed positions.
The gearbox handwheel can be secured to the gearbox input shaft by the pin, or by the key and the
retaining screw. The close direction indicator must be visible on the end of the input shaft, and ensure
that the retaining screw is tightened down. Gear unit stops should also be checked to ensure correct plug
port alignment.
2.4 LOCK DEVICE
Where provided (optional) the valve has a locking lug that allows valve to be locked in full open or full
closed position.
2.5 THROTTLING SERVICE
Valves used to regulate the rate of fluid flow may be subject to severe fluid turbulence. This turbulence
can create a high-energy conversion within the valve and piping system. High noise levels indicate energy
conversion either by the disturbance of liquids or by shock waves from gases. An example of low-level
cavitation noise is the sound made by water in water pipes or a faucet. There is a possibility for
mechanical damage to the valve and piping system when throttling of liquid flow results in severe and
continuous cavitation conditions. Similarly, shock waves can result in damage to the system with gas flow
under severe throttling conditions. APV personnel should be consulted on proper valve selection for
throttling applications.
2.6 PRESSURE SURGE
Closure of a valve in a flowing fluid line will cause the flow rate of the fluid to be reduced to zero. If the
fluid relatively incompressible liquid, the inertia of an upstream column produces a pressure surge at the
valve, the magnitude of which is inversely proportional to the time required for closure. The surge
pressure is also proportional to the length of the upstream fluid column and the fluid velocity prior to
closure initiation. If the application involves a long upstream line, a long downstream line, high velocity,
and/or rapid closure, separately or in any combination, the possibility of an unacceptable pressure surge
should be investigated.
