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4. Belt Adjustment
The QSVB is equipped with an automatic belt-tensioning device and requires no adjustments between belt
replacements.
NOTE:
Belts must be replaced when automatic belt tensioning indicator dowel pin has reached full length of travel in
its groove
.
5. Belt Drive Inspection Procedure
1. Inspect sheave grooves for nicks.
2. Thoroughly inspect the tapered bore of the sheave and the tapered surface of the bushing. Any paint, dirt, metal
chips, fluid or grease MUST be removed.
3. Position bushing and sheave assemblies and rough align with a metal straight edge. Mount sheaves as close to
the vacuum pump and/or motor housing as practical to avoid excessive bearing and shaft loads. Tighten dry
capscrews evenly and alternately. Use no lubricants in this installation. Excessive capscrew tightening can
cause sheave and/or bushing breakage. Rotate pulleys to check for sheave runout wobble) or a bent shaft. Hand
tighten setscrew over keyway, if required.
NOTE:
After tightening, there should be a 1/8” to 1/4” gap between the mating part hub and the bushing flange.
Misalignment of the sheaves will reduce belt life by increasing wear and increase the probability of belt
turnover by decreasing stability. Misalignment comes in three varieties: Horizontal angular, vertical angular
and parallel. Sheave alignment should be within 0.07” per foot of shaft center distance. This is the total of all
parallel and angular misalignment. Check sheave misalignment in at least three places (rotating one of the
sheaves 120° after each check) to locate the position of maximum misalignment.
Types of Misalignment
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