No. D-88218 W
ATER
C
I RCULATING
S
YSTEM
The No. D-882 18 Water Circulating System consi sts of a \\·ater circu lating
pump, a radiator, an expansion tank, control valves and the necessary pi p i ng
to connect the system to the tra nsmitter. This system provides for the d i ssipa
tion of the heat developed on the anode of the No. 228-A Vacuum Tube. T h i s
heat, unless dissi pated as rapidly as produced, w i l l destroy the tube w i thin a
short time. For th is reason, the transmitter is 1wovided with a device wh ich
automatically removes all power from the No. 228-A Vacuum Tube whenever
the water flow is materially reduced due to obstr uction in the system or for
other reasons. Protection is afforded by the use of a Venturi Tube in conj unc
tion with a No. 226-A Relay. Contacts are provided on this relay wh ich are
No.
226-A
Relay
operated by the motion of two opposed metal bellows. The operation of the
relay is as follows : Pressures of different magnitudes which are establ ished at
two separate points i n the Venturi Tube by the water flow i n the system,
are
transmitted through tubular connections to the metal bellows. The differential
pressure established i n the bellows causes one to expand and the other to con
tract, closing or opening a contact through the medium of a multi-lever and
push rod.
The correct water flow is obtained by adj usting the i nlet valve so that a
differential pressure of not less than 1 5 pounds and not more than 22 pounds
is indicated on the two gauges connected w i th the No. 226-A Relay. The differen
t ial pressure is read as follows : When the u pper gauge indicates a vacuum
( i .e., to the left of the "O" ) the differential pressure i s the sum of the two
gauge readi ngs. When the u pper gauge indicates a pressure ( i .e., to the right
of the "O" ) the differential pressure i s the difference between the two gauge
readings.
Inside of the Amplifier Unit in front of the two No. 212-D Vacuum Tubes
are the controlling handles for two valves at the bottom of the Amplifier Unit.
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