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Section 5 • Maintenance/Service
Drive Coupling Hub (Form-Flex BPU)
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.
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 lock-out/tag-out procedure. Compressors
must be depressurized before attempting to do any
work on them. 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 contact
pattern. If bore is straight, measure bore and shaft
diameters to ensure proper fitting. The keys should
have a snug side-to-side fit in the keyway with a
small clearance over the top.
Shaft Gap for Tapered
Coupling
Compressor &
Size
Straight Motor Shaft
Combination
BP38U
BP41U
BP47U
6.25"
(158.75 mm)
BP54U
BP54U
BP56U
5 – 24
NOTE
Shaft Gap for Straight
Compressor &
Straight Motor Shaft
Combination
5.125"
(130.18 mm)
VSS/VSM/VSH/VSSH • Installation, Operation and Maintenance Manual • Emerson • 35391SD
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.
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 5-4.
7.
Install clamping bolts in hub.
8.
Tighten clamping bolts, see Table 5-5.
9.
Install set screw in hub to secure key.
10. Tighten set screw, see Table 5-5. Repeat steps for
second straight bore hub.
Tapered Bore Hubs
11. For taper bore hubs, do not use Anti-seize because
this will allow the hub to slide on farther than with-
out, and you may not be able to get it removed.
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.
Distance
Between Hub
Faces
Table 5-4. Shaft and Hub
5.00"
(127 mm)
NOTE
Distances
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