Quite often, WPT encounters clients in the field who don’t quite recognize the importance of correct clearances and shimming. Some customers are just unaware of the need to adjust the shim stack when it comes to new friction versus used friction. Shimming is also required when conducting maintenance that involves replacing other key internal clutch components.
In a Power Grip or Low Inertia unit, all the internal components have a manufacturing tolerance. When a new unit is assembled, it is shimmed to fall within a set clearance range. Each brake or clutch model has a specific operating clearance that can be found in the installation and maintenance manuals. They are also displayed on each assembly drawing. Should there ever be a difference between the manual and drawing, always defer to the drawing.
Clearance is important because the airtube actuator can only travel a certain distance before the tube starts rounding. When the airtube starts to round, it causes a loss of surface area against the pressure plate. Reducing the airtube surface area has a direct impact on torque capacity and may encourage extra slip time. This will impact the performance, accuracy, and generate higher internal heat levels, resulting in unnecessary wear.
When units that use an airtube for actuation are in operation and under normal service conditions, the friction material wears and becomes thinner. To maintain the set clearance range, it is possible to remove shims, thereby extending the service life. Once all shims are removed, it is time to replace the friction discs. When replacing friction discs in a unit, it is very important to add any removed shims back into the assembly and re-check the clearance.
Checking clearance is a relatively straightforward process. Instructions can be found in the unit’s installation and maintenance manual. For additional information on determining clutch measurements, read the article, How to Measure the Operating Clearance in Your Power Grip PO Clutch.
The staff at WPT Power are always here to help, whether it’s with a WPT Power assembly or troubleshooting a fault with a competitor’s compatible unit. If you or any of your maintenance team need some support, please contact WPT Power: https://wptpower.com/contact/
Written By: Brett Emson, Sales Manager Asia Pacific & Africa