Common Factors that Lead to Failure of Blowers

There are several processes requiring low pressure air in industrial and commercial applications. To carry out these processes efficiently, regenerative blowers have become a widely used source for low pressure air. These blowers are common for small air volumes at higher pressures, which are beyond the performance range of centrifugal blowers. Regenerative blowers, unlike centrifugal blowers, operate on compressor laws as opposed to fan laws. Under compressor laws, increases in pressure or vacuum levels result in a higher workloads, and greater heat generation. As pressure or vacuum increases, the volumetric capacity of these blowers decreases. This is the opposite of centrifugal blowers operating on fan laws, where greater volumes increase the work load, and as pressure or vacuum levels increase, volume is reduced, and the work load and heat load are reduced. Therefore different precautions are required for the protection of regenerative blowers.

What are the Main Factors that Can Cause a Blowers to Fail?

There are many reasons, which can cause the failure of a regenerative blowers. In general, the most common reasons for failure are over-temperature, ingestions of foreign matter, or incompatible environments. For each of these conditions, there could be a number of installation/operational issues contributing to the condition.

  • Bearing Failure: Bearing failure can be a condition which can be considered routine maintenance. Bearings used in regenerative blowers are normally shielded sealed ball bearings using high temperature grease. Over several years of operation there will be a routine requirement to replace bearings due to common wear. However, premature failure of bearings can be caused by over-temperature operating conditions. Even the high temperature grease used in the bearings may liquefy and run out through the shields if extreme temperatures are encountered. Drying up of the grease due to high temperature operation may cause carbon build up and failure. Once lubrication is lost in the bearings, failure will result. Unfortunately, if bearing failure is not discovered in the early stages, motor overload and/or loss of tolerance in the impeller housing may result. This could result in motor burn out or a broken impeller.

  • Ingestion of Foreign Matter: This is normally the result of poor or lack of filtration at the intake of the blower. As regenerative blowers may be used for either pressure or vacuum service, there are two different styles of intake protection.

    • For vacuum service, an in-line filter is required to ensure foreign matter from the process is not allowed to enter the blower. As common vacuum applications are dust collection or material conveying, it is essential that this protection is part of the installation.

    • For pressure applications, an air intake filter is required. These may be in the form of either an automotive-style cartridge type filter or a wire mesh strainer.

    Wire mesh strainers may be suitable for clean air applications, but they will allow fine dust and particles to enter the blower. Although some fine dust may pass through the blower without damage, a gradual buildup of dust or materials in the blower can result in a coating of impeller and housing. This may affect the motor workload, clearance between the impeller and housing, or the dissipation of heat through the impeller housing – all of which could result in contingent failures such as motor overload and failure, impeller breakage, or bearing failure due to high operating temperatures.

    The automotive cartridge-style filter option will normally remove particles to less than 10 microns in size, and will almost eliminate the possibility of ingestion of damaging foreign matter. In either case, intake filters will over time become dirty, and restricted. This may cause the blower to operate at high vacuum levels at the inlet, which will result in over-temperature and/or motor overload. The result of operating under these conditions will be premature bearing failure or motor failure. It is imperative that the user check for inlet filter restriction and ensure filters are maintained in a clean condition. A pressure differential gauge and/or switch at the blower inlet would be beneficial in alerting the user to these conditions before they become critical.

  • regenerative-blowers

  • Operation Outside of the Performance Limits: When considering a regenerative blower for an application, whether it be pressure or vacuum, the pressure or vacuum requirements for the applications must be within the blower’s performance capabilities. One characteristic of regenerative blowers, is that the air passing through the blower serves to cool the blower. If the blower is operated at excessive pressure or vacuum levels with insufficient air flow passing through it, higher operating temperatures will result. These higher operating temperatures may result in premature bearing failure.

    Higher pressure or vacuum levels will also result in higher motor loading and possible overload. These pressure limits which are shown on performance curves, must be considered when considering a blower for your application. Improper selection of a blower may increase power consumption or may cause over-pressure or overloading.

    To prevent excessive pressure or vacuum operating levels, a pressure relief valve or vacuum relief valve should be used in almost all applications. Upon initial startup of a blower, the operating pressure or vacuum level, and the normal operating amperage should be checked and recording to ensure they are within the blower limitations. These readings may also be useful for checking against future readings when troubleshooting system abnormalities.

  • Environmental Conditions: Most regenerative blowers are of aluminum construction for the impeller and impeller housing. Motor barrels/stators may be of either aluminum or cast iron. Most windings used in blower motors are copper. Installations where the ambient air contains incompatible chemicals, high salt levels, or extreme moisture can result in damage to the blower. If uncommon gaseous chemicals are present in the environment, a chemical/material compatibility chart should be reviewed before installing. If extremely salty environments (near the ocean) are encountered, corrosion buildup can take place in the blower housings. In these cases, it may be necessary to take precautions such as disassembly and cleaning at various intervals, or fogging when the blower is out of service for extended periods. As long as the blower is operating continuously with air flow through it, these conditions will often not result in problems however, when the blower is idle for extended periods after being subjected to these conditions, interior damage may occur.

  • Vibration: Most regenerative blowers may be mounted in only two positions. The most common is the horizontal position (horizontal shaft), and the second is vertical with the impeller down. Mounting in varying degrees from these positions may cause bearing stress, and/or vibration. The blowers should not be mounted off-level, or on machinery which may transfer vibration to the blower. Mounting instructions should be covered in the manufacturer’s Operator’s Manual, and these instructions should be observed.

Blowers can deliver optimal performance if they are maintained properly, and protected from any operational failure from occurring. Technical support and information is a valuable asset to anyone designing/installing a regenerative blower system. Air Power Products Limited has been selling regenerative blowers for over 35 years. You can rely on us for assistance to ensure you have covered all necessary requirements for a reliable and proper blower installation.