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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 stag-
gered pattern. Some maintenance manuals specify a tightening scheme. If so, the manual scheme shall be fol-
lowed. 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 clockwise/
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
HPLD Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391HP
Torque Wrenches
Nord-Lock
A. The Nord-Lock
many areas in the HPLD 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
®
5 – 29
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