MIL-HDBK-1003/3
b) Do not use vacuum condensate returns. Since high pressure steam
is hotter than low pressure steam, provide adequate cooling legs of
uninsulated steam pipe or a length of finned radiation between the last steam
main takeoff and the drip assembly. Failure to do this will cause the hot
condensate to flash back into steam at the trap. Use vented flash tank as a
solution. Refer to par. 7.3.3.5 for condensate pumps and flash tank.
7.3.3.2
Boiler.
Refer to MIL-HDBK-1003/6.
7.3.3.3
Refer to par. 7.2.2.5.
7.3.3.4
Steam Pressure Regulating Valves. See Figures 22 and 23 for piping
of steam pressure regulating assemblies, and note the following:
a)
Sizing Pressure Regulating Valves
(1)
Analyze flow required for maximum and minimum demand.
(2) Size the pressure regulating valve to handle peak flow.
This will generally result in a valve body that is smaller than inlet supply
line size.
(3) If there is a big turndown ratio between minimum and
maximum flow, consider using two regulator valves in parallel, perhaps sized
for 30 percent and 70 percent of the flow. Consider to flip the settings so
that the small regulator pilot maintains optimum downstream pressure in the
summer and the big regulator pilot is the lead controller in the winter.
(4) Look at the manufacturer's tables to see whether a two
stage assembly should be used with two regulators in series. Sometimes this
is done anyway for redundancy in low pressure installations; with the
downstream regulator controlling to 5 psi, and a upstream regulator set at 7
psi in case the downstream regulator cannot handle a flow surge.
b)
Piping Pressure Regulating Valves
(1) Provide a bypass around the regulator with a globe valve
that has a tight shutoff seat. Size bypass to flow less than wide open
failure flow of the regulator, but not less than regulator design flow.
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