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Types of Lagging
1. Bolted lagging is usually fabric-reinforced, the fabric being
necessary to give proper bolt-holding. This type has no inner
or pulley cover; where no grooving is intended, 1/8” top cover
is the proper minimum, but if the lagging is to be grooved, a
minimum of 1/4” top cover must be used.
Bolted lagging is usually applied in two or more circumferential
strips, applied under tension with the points in the different
strips staggered around the pulley (On flat-faced pulleys, one
strip the width of the pulley may be used).
For open-end pulleys 5/16” or 3/8” diameter flat head elevator
bolts with nuts may be used. Alternate methods include slotted
bolts with tapped holes or self-tapping screws for use in welded
steel pulleys. It is necessary that the bolt heads be sunk below
the level of the surrounding lagging to prevent damage to the
belt as it passes over the pulley. This may be accomplished by
counter-sinking the holes in the pulley or, where the lagging
cover is greater than about 1/8”, it is possible to sink the heads
merely by tightening the bolts.
Ends of the strips should be bolted in a dovetail joint as shown
in Fig. 30. In addition, bolts should be used in rows running
across the face and around the circumference of the pulleys
no further than 10” apart in either direction. Edges of all strips
should be bolted down and it is recommended that all exposed
fabric edges be cemented to keep out moisture.
2. Vulcanized lagging is a sheet of rubber, usually 1/2” thick and
bonded directly to the metal. No fabric is used because no bolt-
holding reinforcement is needed. It is much longer wearing, has
better and more uniform adhesion to the pulley, and eliminates
the hazard of serious belt damage due to a loose bolt.
This type of lagging can be applied in two different ways:
Spiral-wrap method – generally used for lower tension
applications.
A 4” wide strip is recommended for ease of
handling (Fig. 31).
The length of the strip may be calculated by
the formula:
In application by the sheet-wrap method, a beveled lateral
splice is recommended (Fig. 32). The tie gum side should
contact the beveled leading edge for maximum adhesion at
the splice.
3. Grooved lagging should be used on drive pulleys if they
are likely to be wet. The grooves break the film of moisture
between the belt and lagging, thereby eliminating slippage.
Either bolted or vulcanized lagging can be furnished with
grooves. Either type can be grooved in the field with a tire-
groover if there is sufficient rubber to prevent cutting into the
fabric carcass or metal pulley. Herringbone grooving 3/16”
deep and wide spaced 1” apart is recommended (Fig. 33).
4. A modified type of bolted pulley lagging is also available,
featuring replaceable rubber pads that slip into metal guides
bolted or welded to the pulley (Fig. 34).
C x W
L =
––––––––––––
+ C
4
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Installation, Maintenance & Troubleshooting Guide
Installation