Flowserve 50165 Nordstrom Figure - Manual (Page 17)

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Nordstrom Figure 50165 and 50169 Dynamic Balance Iron Plug Valve FCD NVENIM2006-00 – 09/05
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Mechanical or high intensity fluid noise in the vicinity of a valve may be a warning of potentially serious
trouble. Expert assistance should be obtained from system engineers or the valve manufacturer to
determine the cause and evaluate possible need for action.
Noise emitted from a closed valve is a special case that may indicate seat leakage requiring repair. A
whistling sound may indicate sever erosion of seating surfaces while “gurgling” or “popping” sounds
may signify less severe leakage.
Maintenance
Valves are properly considered to be a hybrid structure, a combination of a pressure vessel and oper-
ating machinery. Maintenance procedures therefore, must reflect the requirements of the occasional
opening or closing of the “machinery” and the predominant operating condition of the valve where
pressure is continuously applied and nothing is moving. The important performance parameters are
pressure boundary integrity, actuating effort required and internal leak tightness. Maintenance should
logically address the importance of preserving these performance parameters.
Valves that remain in one position for long periods of time may be hard to operate and/or not function
as well as when originally installed. This reduction of operability can result from either a loss of effective
lubricants, aging of packing, surface corrosion of moving parts, or an accumulation of deleterious
solids. In some applications it may be desirable to schedule periodic partial or full cycle exercising of
such valves.
Pressure boundary integrity requires basically sound pressure-containing parts, a pressure-tight static
seal at assembly joints and in most cases, an effective working seal between a moving stem and the
valve body. Maintenance of pressure boundary parts and the static seal of assembly joints are not
usually considered to be a problem. However, continuous monitoring is recommended to confirm that
problems do not occur. The need for paint protection against corrosion of exposed piping should be
obvious from normal observations of the system.