2.3.7.5
Seals
Separate air and oil shaft seals shall be provided to confine air in the
casing and prevent contamination of the air stream by lubricating oil.
Shafts seals shall be labyrinth type, carbon ring type, or a combination of
the two types. Provide an air space vented to the atmosphere between the
air and oil seals. Seals shall be suitable for all operating conditions
including suction throttling, start-up, shutdown, and momentary surge.
2.3.7.6
Thrust Bearings
Axial impeller thrusts shall be absorbed by thrust bearings on the pinion
or transferred to the bull gear shaft by conical rider-ring thrust collars.
Pinion thrust bearings shall be hydrodynamic (fluid film), multiple-segment
type, entitled pad type, or other approved type, and shall be adequate to
accommodate all operating conditions, including surging or stonewall
operation. Bull gear thrust bearings shall be sized for equal thrust in
both directions and shall be adequate for any axial loads transmitted
through the driver coupling.
2.3.7.7
Radial Bearings
Radial bearings shall be hydrodynamic (fluid film), precision bored sleeve
or pad type, designed for easy replacement by a split design or axially
removable arrangement. High speed pinion bearings shall be anti-oil whip,
tilting pad, tilted pad, or other approved type. Bearing design shall
provide low vibration and sufficient damping at rated speed and all
operating modes, including rated capacity and unloading down to 15 to 20
percent of unloaded power.
2.3.7.8
Intercooler, Aftercoolers, and Oil Coolers
Intercoolers, aftercooler, and oil cooler shall include admiralty brass [or
copper] tubes conforming to ASTM B 111/B 111M in admiralty tube sheets
conforming to ASTM B 171M ASTM B 171 with plate fins and baffles for
optimum cooling and fouling resistance using [fresh] [_____] water.
Provide an intercooler between stages of compression factory assembled on
unit base with piping. The aftercooler may be mounted separately.
Intercoolers, aftercooler, and oil cooler shall be factory tested at 1.5
times operating pressure. External intercoolers and aftercooler shall be
constructed in accordance with ASME BPVC SEC VIII D1, requirements and be
ASME code stamped for 1207 kPa (gage) 175 psig working pressure.
Intercoolers and aftercooler shall be capable of one piece bundle removal.
Each intercooler shall be equipped with an integral or direct connected
moisture separator with condensate trap or automatic drainer valve
assembly. Piping to drainer and drainer assemble shall be Class 300
stainless steel. Design intercoolers and aftercooler for 11 and 8 degrees C
20 and 15 degrees F approach, respectively, and a fouling factor of 0.001
for both sides of exchanger; however, the approach temperature used to size
the coolers shall be reduced if required to meet aftercooler maximum air
outlet temperature specified. Nonstandard coolers shall be provided if
required to meet the aftercooler maximum air outlet temperature
requirement. All coolers shall be of counter-flow design.
2.3.7.9
Lubrication System
Include reservoir, shaft driven positive displacement pump, twin oil
coolers, twin filter/strainer (readily replaceable cartridges while
operating) and parallel piping and valving provisions to accommodate a
SECTION 15213N
Page 20
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