Experienced industrial fan service technicians with access to Northern Blower resources worldwide keep our customers up and running. State-of-the-art diagnostic equipment is used to provide the following industrial fan services:
- Oversight of the erection and commissioning of new equipment and retrofits
- Field vibration analysis
- Laser drivetrain alignment
- In-situ balancing
- Field performance testing
Why is alignment critical?
Alignment in your machines is vital to the reliability of your operations. When two devices (motor shaft to fan shaft, for example) are misaligned, severe failure can occur, causing unplanned downtime and loss of revenue. Some negative consequences are seal failure, bearing failure, energy loss from inefficiencies, increased vibration, and excessive heat.
Both devices’ shafts must be collinear for regular operation, meaning they are in the same line. There are two types of misalignment: offset and angular (Figure 1). Remember that your machines can have both offset and angular misalignment simultaneously.
To check the alignment of your devices, a dial indicator or laser technology should be used to test the alignment accurately.
Here are the steps we use to align motors and fans:
- Safety Check: Follow your Lock Out Tag Out (LOTO) procedures to ensure no energy is present in or available to the systems you are working on. Once the LOTO procedure is complete, safety guards are removed to access adjustment points.
- Mounting Check: All mounting surfaces and conditions are checked before installing the motor. The feet and the mounting base should be clear of rust, paint, or dirt.
- Soft Foot Check: A dial indicator or laser can be used to check the motor for soft foot (distortion of the equipment frame). If the soft foot is unaddressed, a false alignment of the bearings internally can occur cocking one or both bearings in the housing and putting tension on the bearings. IEEE 1068‐2015 specifies a coplanar tolerance of 0.005 inches (0.127 mm) of the motor feet on a fully assembled motor.
Follow the alignment tool manufacturer’s procedure for performing a laser or reverse dial indicator alignment, keeping in mind the coupling manufacturer’s specified alignment tolerance. This will vary depending on the type of coupling.
A Straight edge
A straight edge should only be used for rough alignment, as this method will not meet the coupling manufacturer’s required tolerance.
B Reverse dial indicator
If done correctly, the reverse dial indicator will produce an accurate alignment per the coupling manufacturer’s specified tolerance. However, this method, though accurate, is time-consuming compared to laser alignment.
C Laser alignment
If properly used, a laser alignment tool will also produce an accurate result per the coupling manufacturer’s specified tolerance. Additionally, this method is less time-consuming than alignment by reverse dial indicators.
Before starting to perform the alignment, the thermal growth of the fan must be determined. In the case of a laser, this allowance must be entered into the program, so the final alignment “cold” will show the alignment is correct and if a “hot” alignment is performed, the laser, less the thermal growth allowance, will be within the manufactures allowable operating tolerance for the coupling.
When using a reverse dial indicator, a cold alignment should be performed. Then the motor should be shimmed by the calculated thermal growth of the fan at 4 points, the motor growth being subtracted from the fan growth to determine the shimming required.
The formula used for this thermal growth calculation is often called the T x L x C formula. T represents the change in the temperature of the material in degrees Fahrenheit, L represents the length in inches of the material (motor base plate to the center of shaft and fan bearing base plate to the center of the shaft.), and C represents the linear coefficient of thermal expansion.
COMMON MATERIALS AND THEIR C-VALUES
If the thermal growth calculations are such that the final alignment will be within the coupling tolerance, without the addition of shims or the addition of the thermal growth difference being entered into the laser, there would be no need to add the thermal growth amount to the laser or to shim the motor after the reverse dial indicator procedure.
Only experienced employees, trained and certified in the methodology (laser or reverse dial indicator), should perform the alignment as this is critical to the operation of the equipment.
Using a vibration analyzer, a final check at operating temperature should be performed across the coupling to ensure no issues, regardless of whether or not there is an allowance for thermal growth.
If you have questions, our service team is ready to help!
Northern Blower Service: (204) 222-4216 or email@example.com