Section 5 • Maintenance/Service
Drive Coupling (Form-Flex BPU) Hub Installation
On all single screw units, the coupling assembly is shipped loose and will have to be installed and aligned on site. This is to allow a check of proper electrical phas- ing and direction of motor rotation. The motor and compressor have been aligned from the factory with the coupling hubs already installed. Using a dial indicator for aligning is recommended.
with a small clearance over the top.
NOTE
If hub position on shaft does not allow enough room to install bolts, install bolts and disc pack before mounting hub on shaft.
Hubs come in two different types, straight bore and tapered bore. Tapered bore hubs have additional hardware. Typically, a compressor will have a tapered shaft and therefore use a tapered bore hub.
NOTE
Drive coupling type and size can be determined by the information on the compressor nameplate when ordering; Order Number and Compressor Model Number.
To install the coupling, proceed with the following steps:
WARNING
Follow local lockout/tagout procedure. Failure to comply may result in serious injury, death and/or damage to equipment.
1.Ensure disconnect switches are in the OFF position for the compressor unit and oil pump motor start- er, if equipped.
2.If hubs are already installed on motor shaft and compressor shaft, proceed to Drive Center Member Installation and Alignment procedure.
3.If coupling assembly is already assembled, the lock nuts are not torqued. Remove lock nuts and bolts securing hubs to disc packs. Remove both hubs. Leave the disc packs attached to center member.
4.Clean hub bores and shafts. Remove any nicks or burrs. If bore is tapered, check for good con- tact pattern. If bore is straight, measure bore and shaft diameters to ensure proper fitment. The keys should have a snug
STRAIGHT BORE HUBS
5.For straight bore hubs, install key in keyway of shaft.
6.Install hub on shaft. If installing straight bore hubs on motor and compressor shafts, allow 1/16” gap between the outer face of the hub to the outer face of the shaft for both hub installation. This will allow some play when installing the spacer. If installing a straight bore hub and a taper bore hub, allow a 1/8” gap between the outer face of the straight bore hub to the outer face of the straight shaft, see Table
7.Install clamping bolts in hub.
8.Tighten clamping bolts, see Table
9.Install set screw in hub to secure key.
10.Tighten set screw, see Table
TAPERED BORE HUBS
11.For taper bore hubs, install key in keyway of shaft.
12.Install hub on shaft.
13.If lock washers are being used, install hub cap, lock washers and bolt on shaft.
14.If locking tab is being used, install hub cap, locking tab and bolt on shaft.
15.Tighten bolt and draw hub up shaft to a stop.
Table 5-3. Shaft and Hub Distances
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| Shaft Gap for Tapered | Shaft Gap for Straight | Distance |
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| Coupling | Compressor & | Compressor & |
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| Between Hub |
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| Size | Straight Motor Shaft | Straight Motor Shaft |
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| Faces |
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| Combination | Combination |
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| BP38U |
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| BP41U |
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| BP47U | 6.25” | 5.125” | 5.00” |
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| BP54U | (158.75 mm) | (130.18 mm) | (127 mm) |
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| BP54U |
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| BP56U |
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5 – 10 | VSG/VSSG • Installation, Operation and Maintenance Manual •Vilter/Emerson • 35391SSG |
