Flowserve 50165 Nordstrom Figure - Manual (Page 7)


Nordstrom Figure 50165 and 50169 Dynamic Balance Iron Plug Valve FCD NVENIM2006-00 – 09/05
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Trapped Pressure
When a closed valve containing liquid is heated (e.g., from process condition, radiation or solar heating)
the cavity pressure will increase due to volumetric expansion or vaporization of the liquid. Conversely,
cooling an undrained cavity below the freezing point may also result in volumetric expansion of the
media. These expansions can result in extremely high pressures occurring in the valve.
The purchaser should consider the necessity of providing positive means for prevention of such over-
pressurization where these conditions can be anticipated.
Material Compatibility
It is important that valve structural materials and lubricants be chemically compatible with the other
piping system components, line fluids and the environment. Guidance should be obtained from
informed sources such as NAI or the system engineers whenever there appears to be reason for such
concern.
Operating Effort
Manually operated valves are usually designed to require a reasonable amount of physical effort applied
to a handwheels or handle to open or close at rated working pressure. However, typical use of a valve
may involve a lower working pressure thereby substantially reducing the differential pressure across
a valve closure element and a resulting reduced operating effort. Lower operating effort can also be
achieved by opening a bypass valve in some cases.
In all cases, the purchaser should determine that the manually operated valves selected will be capable
of being operated under the anticipated operating conditions by the personnel required to perform such
operation. Oversize handwheels and gear operators will require specific operator training to prevent
applying damaging overloads. NAI should be consulted for specific instruction on operating torques.