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|  MIL-P-18547A(SHIPS)
3.6.15.4.1 The selectors switch shall be of the three positions, maintained contact type, with markings
"OFF," "AUTOMATIC," and "MANUAL." With the selector switch in the automatic position the motor shall
start automatically when the pressure switch closes on drop in pressure below a predetermined value. Once
started, the motor shall continue to run, regardless of the pressure switch opening on restoration of pressure,
until stopped by turning of selector switch to the off position. An indicator light shall be provided in the selec-
tor switch enclosure to indicate when the switch is in the automatic position. With the selector switch in the
manual position, the motor shall run continuously and the pressure switch shall be completely disconnected
from the circuits to permit adjustment of repair without hazard to personnel.
3.6.15.5 Reduction gears. - Where reduction gears are used, they shall be of the spur, single or double
helical, or worm type in accordance with MIL-G-17859, except that class CO-1 pump gears may be in accord-
ance with applicable practices of the American Gear Manufacturers. Reduction gears shall be independent of
the pump and connected thereto by a flexible coupling. Such reduction gears may, however, be an integral part
of the driving unit.
3.6.16 Attached pumps. -
3.6.16.1 Pumps may also be driven either by a chain drive off the ship's main propeller shaft or by a
power take-off from the ship's main reduction gear as specified (see 6.1).
3.6.16.2 Chain driven pumps. - The arrangement of pumps with respect to the propeller shaft, size of the
propeller shaft, and other details shall be as specified (see 6.1).
3.6.16.2.1 Chain drive. - The pumps shall be driven by a roller chain, or equivalent, as approved by the
bureau or agency concerned.
3.6.16.2.2 The chain shall be provided with detachable links to allow quick disassembly when the propel-
ler shaft is stationary. The chain links shall be locked by cotter pins. A special tool (see 3.10.2) shall be
provided for each pump to facilitate disconnection of the chain. To insure availability, the tool shall be
mounted on the exterior of the chain case. Permanent detail instructions to fully cover chain disconnection
and removal shall be provided. These instruction plates shall be in accordance with MIL-P -15024 and shall
be mounted on the chain case.
3.6.16.3 Sprocket mounting. -
3.6.16.3.1 The pumps shall have the driven sprocket mounted on the pump drive gear shaft. A positive
means of alignment for the driven sprocket shall be provided on the shaft.
3.6.16.3.2 The driving sprocket shall be in two halves, and shall be mounted on the main propeller shaft.
3.6.16.3.3 The driving and the driven sprockets shall be of cast or forged steel.
3.6.16.4 Chain guard. - The chain and sprockets shall be encased in a steel chain guard. The chain
guard shall be provided with hinged, quick-opening covers on at least one side and on the top in an appropriate
location to permit easy access for disconnection and removal of the chain. The chain guard shall be fitted
with a lucite, or equal, window to provide visual inspection of the drive sprocket. The chain guard shall be
provided with substantial means of support.
3.6.16.5 Fabrication. - The lubrication of the chain drive, the gears of the unit, and the pump bearings
shall be provided from the discharge side of the pump.
3.6.16.5.1 The lubricating system shall include a sight feed valve, strainer, and a drain connection.
3.6.17 Rubbing speeds .- The maximum rubbing speed in feet per minute for a particular type pump shall
be the speed established for that type pump during the qualification tests (see 4.5.2).
3.6.18 Theaded parts .- Threaded parts shall conform to Handbook H28.
3.6.19 Welding and allied processes. - Welding and allied processes shall be in accordance with MIL-
STD-278. Cast nodular iron parts shall not be welded.
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