wattage (horsepower) units (375 kW (500 hp) and
below), the drop-pin type backstop is a satisfactory
alternative and may be added to the specification.
Spragtype backstops perform adequately in many
installations but have been more prone to problems
such as wear and excessive heat generation than the
other types and are not listed as an option here.
If a diesel engine is used, the idle speed and
duration should be listed for proper consideration
during backstop sizing.
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A backstop shall be provided on the output shaft to prevent reverse
rotation of the pump. For double reduction reducers, the backstop may be
mounted on the output or intermediate shaft. The backstop shall be sized
for the resulting torque at the reducer during maximum reverse flow at pump
and a service factor of 2.0 shall be applied to the manufacturer's
published rating. In addition the backstop shall be suitable for
continuous operation at engine idle speed of [800] [_____] rpm. The
backstop shall be of a type with cylindrical rollers on inclined cam planes
or drop-pin type. The backstop shall be mounted with the outer race moving
and the inner race fixed. The backstop shall operate at a temperature of
less than 70 degrees C 160 degrees F under all operating conditions with an
ambient temperature up to 40 degrees C 100 degrees F. The backstop shall
be provided with a circulating oil lubrication system and shall have
sufficient flow rate to provide the required cooling. The lubrication
system may be part of the gear reducer lubrication system.
2.7
HOUSING
2.7.1
General
The housing shall be cast or fabricated steel, stress relieved prior to
machining, and reinforced to carry all applied loads and to maintain gear
alignment. A sole plate [as shown on the drawings] shall be provided under
the reducer. The sole plate shall be installed, leveled and grouted in
accordance with API RP 686, Chapter 5 - Mounting Plate Grouting. Jacking
bolts shall be provided for leveling the sole plate. All leveling jacking
bolts shall be backed off after grouting so that they do not support any
part of the load. An anchor bolt layout shall be provided to aid in
placement of the anchor bolts. The housing bottom shall be machined. The
interior of the reducer shall be painted with an oil compatible coating.
The exterior shall be painted with the manufacturer's standard coating
system. Color shall be light gray. The housing shall have an oil fill
connection and a drain connection with a magnetic plug. Lifting lugs shall
be provided for lifting the entire reducer assembly and any subassembly or
component which cannot be lifted using web slings.
2.7.2
Seals
Vertical down output shafts shall have a drywell design seal. The input
shaft shall have a lip seal to prevent leakage of oil and exclude dirt.
Lip seals shall utilize hardened steel wear sleeves to preclude shaft
repair or replacement if the seal wears the shaft.
2.7.3
Inspection Covers
The housing shall have inspection holes with cover plates located above the
maximum oil level to permit viewing of gear teeth allowing evaluation of
SECTION 15005A
Page 13
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