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 Nitrogen Pressurized HTW Separate Pumping System
FIGURE 4-2.
W h e r e it is mandatory that a boiler circulating system be isolated
f r o m the distribution system
Separate pumping systems are usually provided with
6 . 3 Alternate Equipment.
the following equipment.
( a ) Temperature Control Valve. T h i s automatic valve is installed in the
I t serves the
blending line to the suction of the system circulation pumps.
same purpose described for combined systems in 6.1(b) above. The valve is
furnished with a manual bypass. The purpose o f the manual throttling valve,
w h i c h is installed in the return line supplyi n g the boiler recirculation
pumps, is to create a pressure drop, thereby f a c i l i t a t i n g o p e r a t i o n o f t h e
temperature control valve.
( b ) Automatic Closing Valves. These are motor operated valves provided
to isolate the using end of the system should a major break occur in the
supply or return mains. They are set to close when the waterflow exceeds a
predetermined value.
4-7
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