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Alternately, use an automatic wrench set at a low torque value (for example: 25 in-lbs.
[2.8 N·m]). Then use a manual calibrated torque wrench to finalize the torque.
Always torque the bolts in opposing pairs.
12 inch, 6-bolt fixture (See Figure 25):
— Tighten bolt #1, then tighten bolt #4. Next tighten bolts #2 and #5. Finally, tighten
bolts #3 and #6.
(Not shown) 8 inch, 4-bolt fixture:
— Tighten any bolt designated as #1, then tighten bolt #3. Next tighten bolts #2 and #4.
(Not shown) 8 inch, 2-bolt/2-pin fixture:
— Simply tighten bolt #1, then tighten bolt #2.
Figure 25:
6-Bolt Torque Sequence
Use the above guidance for any bolted connection on a load bearing base can. This
includes:
•
6 bolts used on a 12-inch in-pavement fixture.
•
6 bolts used with an 8-to-12 inch in-pavement fixture adapter ring.
•
4 bolts used on an 8-inch in-pavement fixture.
•
2 bolts/2-pins 4 bolts used on an 8-inch fixture.
•
Snow plow ring used on any fixture.
WARNING
When a stainless steel base can is used, take steps to insure that galling
does not occur. Galling is often referred to as a cold-welding process, which
can occur when the surfaces of male and female threads come in contact
under heavy pressure. The risk of galling can be minimized with the
following measures:
— Thread lubrication is one of the most effective measures to lessen the
potential for galling. The lubricant reduces friction, which is a key
element in thread galling. Avoid installing a stainless steel bolt dry with
no lubricant.
— Heat contributes significantly to thread galling. Installing a bolt
generates heat and high-speed installation generates significantly
more heat. Torque the bolt slowly into the base can.
— Do not use an impact wrench to torque the bolt quickly, resulting in a
torque beyond 500 ±10 in-lbs. (56.5 ± 1.1 N·m). If the fastener is over
tightened, the threads can begin to yield which will induce friction
between the mating surfaces.
