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Impellers shall be cast of high grade [aluminum alloy] [steel], mounted and
keyed to the shaft and secured by a locknut. Impeller hubs shall butt
against each other either directly or through one piece metal spacers.
There shall be ample clearance between the impeller and casing. Each
impeller shall be tested by being operated at a speed to [20] [_____]
percent above operating speed and checked for cracks using the dye
penetrant method or similar method of equal accuracy. The impeller and
shaft assembly shall be statically and dynamically balanced as a unit.
Removing of metal from the impeller by boring is not an acceptable means of
balancing the impeller and shaft unit. Vibration shall not exceed 0.025 mm
1.0 mil at the bearing housing with the blower operating. First critical
speed shall be at least 150 percent of maximum operating speed.
2.3.1.4
Diffusers
Diffuser vanes, cast into each section of the blower casing, shall be
provided to receive air from the impeller and direct the air to the next
impeller for multi-stage type blowers.
2.3.1.5
Shaft
The shaft shall be ground and polished high grade [high alloy steel]
[carbon steel] of sufficient diameter to operate below first critical speed.
2.3.1.6
Shaft Seals
Solid carbon ring shaft seals shall be provided where the shaft passes
through the inlet and discharge heads. Seal design shall permit seal
inspection or replacement without disconnecting suction or discharge piping.
2.3.1.7
Internal Seals
Labyrinth type seals shall be provided between stages.
2.3.1.8
Bearings
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NOTE: Delete inapplicable lubrication method.
Verify bearing L-10 life requirements.
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Each blower shall be provided with two [pressure oil lubricated sleeve type
journal] [splash oil lubricated anti-friction type] bearings. Bearings
shall be designed for both radial and thrust loads and sized for an L-10
life of 5 years continuous operation as defined by ABMA 9 or ABMA 11. It
shall be possible to replace the bearings without disassembling the blower
casing or disconnecting piping.
2.3.1.9
Pressure Oil Lubrication System
A console mounted pressure lubrication system shall be provided to oil the
sleeve bearings. The system shall consist of a main oil pump mounted on
and driven by the blower shaft, an auxiliary electric motor driven oil
pump, an oil cooler, an oil filter, a 3-minute retention time oil
reservoir, and all required switches, temperature sensors, and gauges. The
electric motor driving the auxiliary oil pump shall have Class F
insulation, Type NEMA Design B, in accordance with NEMA MG 1, and shall be
SECTION 11375A
Page 13
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