Hydro-Pneumatic House Pump System
Bulletin 258
* Maintains Uniform Building Pressure
* Boosts Supply Pressure as Required
* Automatic Control of Pumps and Compressor
* Single and Duplex Units
* Pumps Operate Only When Required
* Long Operating Life
GENERAL DESCRIPTION:
The Federal Type SK Hydro-pneumatic House Pump System is a popular solution for
the problems of furnishing steady building pressure with varying supply pressure
and building demand rates. These systems utilize standard pumps, motors and
compressors plus hydro-pneumatic tanks sized to require pump operation only
during periods of high demand.
OPERATING PRINCIPLES:
SK Systems utilize standard Federal pumps. No pump or motor modifications are
required. The pumps can be selected from any standard Federal line, including
end suction close-coupled (Bulletin 177), end suction flexible coupled (Bulletin
178) or double suction horizontally split case (Bulletin 185). The pumps can
operate at any of the standard speeds (3450, 1750 or 1150 RPM).
An automatic pump and compressor controller is mounted on the hydro-pneumatic
tank (similar to Heally-Ruff Roto-trol or Autocon Duotrol), which starts the
pumps when the pressure in the tank drops to the bottom of the tank operating
range. The controller will also start the compressor when the water level begins
to encroach on the required air cushion. Therefore, the air cushion and pressure
of the tank are automatically maintained.
Because of the compressibility of air, the water can be supplied to the
building at the proper pressure during periods of low demand without the
necessity of turning the pumps on.
SINGLE & DUPLEX SYSTEMS:
SINGLE SYSTEM: A single SK System includes one pump, one compressor, a magnetic
starter for each of the two motors, plus an automatic pump and compressor
controller.
DUPLEX SYSTEM: A duplex SK system includes two pumps, one compressor, a
magnetic starter for each of the three motors, plus an automatic pump and
compressor controller with a built-in alternator to alternate the operation of
the two pumps.
ACCESSORIES:
It is recommended that cork isolation mats or rubber-in-shear rails be used
under the pumps and compressor. Fed-Flex hose connections should be used on pump
suction and discharge lines and on the compressor discharge line.
The compressor should be complete with belt guard, loadless starting device
and filter-muffler A spring-loaded soft-seat check valve should be provided for
pump and compressor discharge lines. The hydro-pneumatic tank should be fitted
with gauge-glass, piers or saddles, relief valve and pressure gauge. The
compressor can be manually controlled, if preferred.
Modifications for SK Systems include: combination starters and disconnect
switches, encl~eed duplex control panels for wall or floor mounting, watertight
or explosion-proof motor and control enclosures.
SIZING THE PUMPS
PUMP CAPACITY: The gallon per minute rating (GPM) of the pump can be determined
from the tables shown below, based on the total number of fixtures to be
serviced. The GPM rating determined applies to the pump of a single SK System
and to each pump of a duplex SK System. Note that if special water demand is
present in a building (such as a swimming pool, process work, laundry, etc.) add
additional pump capacity to cover such special demand.
TOTAL DYNAMIC HEAD (TDH) OF PUMP:
The total dynamic head of the pump includes the height from the pump to the
highest fixture (static head), plus friction loss thru pipe and fittings, plus
required residual pressure at the highest fixture, plus tank operating range,
minus minimum available street pressure.
EXAMPLE:
Static head --- 120 ft.
Friction loss (can be estimated at 25% of static head)
--- 30 ft.
Required residual pressure (usually 20 psi) --- 46 ft.
Tank operating range (usually 20 psi) --- 46 ft.
Total So Far (120ft. + 20ft. + 46ft. + 46ft.) ---
242 ft.
Less street pressure available (varies by time of day and season, use
minimum) --- 57 ft.
Total Dynamic Head of pump --- 185 ft.
SIZING THE TANK
Total tank capacity should be 25 times the GPM rating of the pump (Example: pump
capacity is 200 GPM, total tank capacity is 5000 gallons). Tank size can be
selected from tank manufacturers' standard tables.
SIZING THE COMPRESSOR
The compressor should be rated 2.5 cubic feet per minute (CFM) for each 3000
gallons of tank capacity (Example: total tank capacity is 5000 gallons,
compressor rating is 4.2 CFM). Compressor should be rated at an intermittent
working pressure higher than the maximum system working pressure (usually 100
psi, 150 psi or 200 psi).
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Specifications
Duplex SK System with Automatic
Compressor Control
Single SK System with
Manual Compressor Control
