MIL-HDBK-1003/1
(f) Controls. The controls of a hydro-pneumatic system are to maintain the predetermined pressures, water levels, and air-water ratio within the tank. When duplex pumps are provided, controls are to start only one pump at a time. Pumps are to be operated alternately and run
simultaneously only when the predetermined low pressure cannot be maintained by a single pump. Controls are to admit compressed air into the tank only when tank pressure at high water level is below normal.
(g) Booster Pumps. Booster pumps may be the "on- off" type or continuous running type.
(I) On-Off Type. The installation of an "on- off" type of pumping system should be considered when relatively long periods of pump-on or pump-off are
anticipated. Pumps are to be activated, only when pressure is inadequate, by a sensing device located in the pump suction line. Flow normally is through a single full-size pump bypass with check valve and two normally open (N.O.) isolating
valves, whether the installation has one pump or multiple pumps. Provide each pump with a check valve on the discharge and two N.O. isolating valves.
(II) Continuous Running. Variable speed, constant pressure, continuous running pumps are to be considered when anticipated pressure fluctuation would result in short-cycling of the "on-off" type of pumps. Whether the installation is a single pump or multiple pumps, provide one full-size pump bypass having a check valve and two N.O. gate valves. Provide each pump with a check valve on the discharge and two N.O. isolating valves.
Add "SECTION 607.2.3 Rate of Circulation. Circulation should be at a rate that limits the water temperature drop to
20 degrees F (6.7 degrees C) (maximum temperature difference
between supply and return). A method that has proved
satisfactory and is generally accepted for determining rate of
circulation is to allow 1 gallon (3.8 liters) per minute for
each 20 fixtures using hot water. Valves for balancing the
circulation should be provided in each return branch."
SECTION 712.3.1 Sump Pump. Add the following. "Provide a single pump unit where the function of the equipment is not critical, and provide duplex pump units where the function of the equipment is critical and also where six or more water
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