transmitting power from the motor to the mixer shaft. The reducer shall be
either V-belt drive or gear drive type. Reduction ratio shall be as
required for proper mixer operation.
2.4.2.1
V-Belt Speed Reducer
The unit shall consist of sheaves and V-belts, properly sized for the
required horsepower transmission. Belts shall be of the static-conducting
type for operation near digester gas. A means of adjusting belt tension
shall be provided. An enclosure shall be provided to protect the unit from
weather and to protect personnel from injury.
2.4.2.2
Gear Reducer
The unit shall consist of gears, shafts, and bearings, mounted in a cast
metal housing. Unit shall be sized to transmit the intended horsepower.
Lubrication shall be by oil bath and the unit shall have provision for
filling, draining, and checking the oil level. Seals shall be provided on
all shaft penetrations to prevent the escape of oil and the entry of
contaminants. A vent shall be provided to allow the entry and escape of
air. The vent shall be designed to minimize contaminant entry.
2.4.3
Shaft
A cold-rolled steel shaft, [_____] mm feet long, shall be provided for
support and rotation of the [impeller] [or] [propeller]. The shaft shall
be designed to prevent excessive deflection under normal load conditions.
The shaft shall extend from the speed reducer unit through the bearing and
support assembly to the [impeller] [or] [propeller].
2.4.4
Bearing and Support Assembly
A cast metal unit, complete with bearings, shall be provided for the
support of all other mixer components. The assembly shall mount directly
on the digester [cover] [wall] and shall provide a gas tight seal. The
unit shall contain two bearings, mounted sufficiently apart from each other
to give stable support to the shaft. Bearings shall be self-aligning
roller or ball bearings designed for axial loading and sized to support the
shaft and [impeller] [or] [propeller] under all load conditions. The
assembly shall have grease fittings, passages, and relief ports as required
for proper bearing lubrication.
2.4.5
Seals
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NOTE: Coordinate with Section 13234A FLOATING COVER
FOR SLUDGE-DIGESTION TANKS. Coordinate with
paragraph COMPRESSED GAS SLUDGE MIXING SYSTEM.
**************************************************************************
Shaft seals shall be provided at the top and bottom of the bearing and
support assembly. The upper seal shall both retain grease and prevent the
entrance of contaminants. The lower seal shall be designed to retain
grease and to prevent the passage of digester gas under [_____] kPa psi
pressure.
2.4.6
Impeller or Propeller
An [impeller] [or] [propeller] shall be provided on the end of the shaft to
SECTION 11380
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