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Section 5 • Maintenance/Service
Using A Torque Wrench Correctly
USING A TORQUE WRENCH CORRECTLY INVOLVES FOUR PRIMARY CONCERNS:
A. A smooth even pull to the break point is required. Jerking the wrench can cause the pivot point to break early
leaving the bolt at a torque value lower then required. Not stopping when the break point is reached results in an
over torque condition.
B. When more than one bolt holds two surfaces together there is normally a sequence that should be used to
bring the surfaces together in an even manner. Generally bolting is tightened incrementally in a diametrically
staggered pattern. Some maintenance manuals specify a tightening scheme. If so, the manual scheme shall be
followed. Just starting on one side and tightening in a circle can cause the part to warp, crack, or leak.
C. In some cases threads are required to be lubricated prior to tightening the bolt/nut. Whether a lubricant is used
or not has considerable impact on the amount of torque required to achieve the proper preload in the bolt/stud.
Use a lubricant, if required, or not if so specified.
D. Unlike a ratchet wrench a torque wrench is a calibrated instrument that requires care. Recalibration is required
periodically to maintain accuracy. If you need to remove a bolt/nut do not use the torque wrench. The clock-
wise/counterclockwise switch is for tightening right hand or left hand threads not for loosening a fastener. Store
the torque wrench in a location where it will not be bumped around.
Fine Serration Face Out
Coarse Serration
Mate Together
VSS/VSM/VSH/VSSH • Installation, Operation and Maintenance Manual • Emerson • 35391SD
Torque Wrenches
Nord-Lock
A. The Nord-Lock
areas in the single screw compressors that require a
vibration proof lock washer.
B. The lock washer set is assembled so the coarse
serrations that resemble ramps are mated together.
C. Once the lock washer set is tightened down, it
takes more force to loosen the bolt that it did to
tighten it. This is caused by the washers riding up
the opposing ramps.
Washers
®
lock washer sets are used in many
®
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Troubleshooting
