Blower System bases can be classified as elevated, non-elevated or sole plates. An elevated base is sometimes referred to as a "table top" base. Non-elevated bases are typically formed steel or a structural steel weldment mounted directly to a foundation. Soleplates are typically steel plates mounted in a concrete pad. Elevated bases are typically used in systems below 150 HP; however, Blower System have been built with much higher horsepower in this configuration. Blower System are typically larger machines in the vertical (side inlet and discharge) configuration. Soleplates are usually reserved for installations requiring 500 HP or greater.
Drive alignment is an important factor in the longevity of a Blower System. V-Belt drive and flexible coupled are the most common forms of drive. Our experience has been that v-belt driven Blower System are the most prevalent. Important considerations when v-belts are used are as follows:
- Check the overhung load of the Blower System and motor to insure that the maximum limits are not exceeded. Overhung load is the pull exerted on the blower shaft. Refer to the operating manual of the unit for maximum limitations. Excessive load can dramatically shorten the life the drive bearing. In extreme cases it may cause the shaft to fail at the bearing. Typically, overhung load problems can be avoided by using a moderately sized sheave on the blower. Based on a load calculation, smaller sheaves cause greater overhung load for a specific ratio then a larger diameter sheave.
- Confirm that the belts are aligned properly. Typically, sheaves should be no more then 1/16" out of alignment, while 1/32" is preferred. Sheave misalignment may cause premature bearing failure as well as cause loss of end clearance in the blower.
- Proper belt tension is important for the life of the blower bearings as well as life of the belt. After a new set of belts is installed, they should be retensioned after 24 hours of operation since they tend to stretch. If the belts are tensioned too tightly they can cause an overhung load problem and premature bearing or shaft failure.
- The sheaves should be mounted as close to the blower drive cover as possible to minimize overhung load. Close is considered to be ¼" to ?" on the smaller units and approximately ½" on the larger units.
- V-belts are typically designed with a minimum 1.4 service factor. Verify that this minimum exists. The service factor is based on the maximum continuous horsepower the belts are rated at divided by the actual horsepower requirement of the blower.
Applications of Blower System
A discharge temperature switch is a good control based safety device for constant inlet temperature applications. The temperature switch protects the Blower Systems from excessive temperature rise due to over pressurization. The discharge temperature switch is not well suited for varying inlet temperature conditions. This basically applies to any application that utilizes ambient air. This Blower System can be illustrated by setting the discharge temperature based on the high ambient condition expected.