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| Welcome to the Centrifugal Blower Maintenance Minute,
the 60 second newsletter designed specifically for centrifugal air & gas blower operators. Each month we will feature a different aspect of service and maintenance to centrifugal blowers. We will review operation, troubleshooting, actual case histories, and answer reader questions. |
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| Couplings & V-Belts
Most positive displacement air blowers are driven with v-belts. Blower performance selection is dependant on the blower speed, which is determined by the sheave sizes. Some multi-stage centrifugal blowers have v-belt drives, but they are almost always increasing the speed to attain higher performance. Direct coupling drive is the standard for centrifugals, with "maintenance free" flexible coupling elements being the preference.
 From a maintenance standpoint, flexible couplings are much better than v-belts. Flex elements have a service life of 6-8 years or more! They also have a shelf life, which means you should always check the manufacturer's date prior to installation. The steel, or cast iron, hubs are not a wear item, so they may last longer than the equipment! Obviously, shaft alignment is critical to coupling life.
Lubricated direct drive couplings can last even longer if they are lubricated properly. Grease lubricated couplings(grid type, or gear type) need to be serviced annually: have the old grease cleaned from the coupling, inspected, and re-packed with fresh new grease. The coupling manufacturer's "long term grease" can extend the clean & repack up to 5 years. The larger, high torque couplings, can cost many thousands of dollars, but they are designed to last the life of the machines they are coupling.
 Flexible element couplings need only to be inspected once per year to check for loose bolts, fatigue cracks in the flex material, discoloration, or unusual wear. They are truly "maintenance free". Since all couplings are specifically designed for the given application, it is most important the replacement is of the same size and material. Imbalance of new couplings is rare, but is quite possible. Oftentimes lower vibration levels can be achieved simply by adjusting the alignment of the keys-if in-line, offset 180O, or vice versa.
 V-Belt drives can be a maintenance nightmare. New sheaves & v-belts need to be tensioned prior to startup, and then re-tensioned regularly throughout their life. Monthly tensioning to start, and then monthly inspections with usually quarterly re-tensioning. Even if the tensioning is maintained, v-belts generally don't last as long as flex elements.
A Tensiometer is used to measure for proper tension. The correct value is calculated from the distance between the sheaves, the size of the belt, the speed, etc... There are charts for general use, but the only good way to be sure you have the proper tension is to do the calculations for each and every machine. In this digital age, the calculation procedures are readily available on the v-belt manufacturer's websites.
 Sheaves are also a wear item-they need to be inspected and replaced periodically. Sheave alignment is critical to longer belt life. As with direct driven equipment, shaft alignment saves money! Not only does it prolong the life of the components to save material costs, but it extends the life of the equipment itself by reducing the load on the bearings and seals.
© Copyright 2009 Snyder Technical Services, LLC. All Rights Reserved
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Maintenance Minute is published each month by Snyder Technical Services, LLC and is based on the work of former Lamson National Service Manager, Bill Snyder. Should you have any questions, or problems to discuss, please contact me.
Bill Snyder
Founder - Snyder Technical Services, LLC |
| Next Month:
Soft Foot = Excessive Vibration...Case History File |
| Thought for Today:
"You learn in life that the only person you can really correct and change is yourself."
--- Katherine Hepburn
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