Flowserve 50165 Nordstrom Figure - Manual (Page 14)

Nordstrom Figure 50165 and 50169 Dynamic Balance Iron Plug Valve FCD NVENIM2006-00 – 09/05
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Operation and Maintenance
Introduction
An industrial valve, reasonably matched to a particular service application and properly installed in a
piping system, can be expected to have a long service life with a minimum of attention. Unlike totally
passive components such as pipe fittings, vessels, etc., valves are a special kind of “machinery”
having moving and wearing parts. The satisfactory performance of these working parts depends on the
long-term preservation of various highly finished surfaces. Therefore, it is important to give adequate
attention to the specific requirements for proper operation and reasonable maintenance of all valves
throughout their service life.
Operation, Manual Valves
Most valves are actuated manually with rotational movement of a handwheel, wrench, handle, etc.
Care is required to assure that such movement is in the correct direction, is not too fast or too slow
and is applied through the proper distance. The terminal positions, open and/or closed, have important
functional significance.
Plug valves do not rely on stem actuating force to provide tight shutoff. However, the correct position of
the closure element in these types of valves is very important. In some cases the effort required to move
the closure element might increase substantially during final approach to the closed position, giving
a false impression of having reached the required position. Failure to get to and stop at the full closed
position can result in leakage and consequent damage to the sealing elements.
Plug valves require correct positioning of the closure element to seal properly. Closing travel should not
stop until a positive stop is reached or a position indicator reaches the “closed” position.
Purchase specifications requiring restrictive maximum forces to be applied on levers or handwheel rims
may also lead to damaging forces being applied to valves or actuators in actual practice as larger forces
are some-times applied in the field. Users should consider this fact in training of operating personnel.
Be sure to consult the gearing manufacturers maintenance manual for more detailed information.