Categories: Shaft Alignment,Machinery Maintenance,Other Topics

How to Read an Alignment Report Part 2 – Thermal Growth Targets

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By on January 23, 2019

The goal of a precision alignment is to align the machine within tolerance when at operating condition. Many, but not all, machines are aligned without the need to compensate for offline to running (OL2R) movement most often associated with thermal growth.

A previous blog post (see link below) discussed how to read an alignment report when thermal growth compensation isn’t required.

On the machine in question the O.E.M. manual instructs the user to compensate for thermal growth in a couple of steps:

1 – Align to tolerance.

2 – Add 14 thousandths (mils) additional shim to all four feet on the motor and recheck.

3 – After rechecking add 18 thousandths (mils) to the front foot of the blower.

With many laser shaft alignment systems this can be simplified by adding the thermal growth targets prior to starting the alignment. This greatly streamlines the alignment process and provides documentation that the alignment was completed to tolerance using thermal growth compensation.

Targets Input Using the Fixturlaser NXA Pro

The OEM’s targets of +18 mils at the front feet of the blower and +14 mils under the motor feet are entered into the NXA Pro as shown below. There is no compensation in the horizontal plane.

Alignment report showing in tolerance with Targets

The Green coupling icons indicate the alignment is within tolerance vertically and horizontally for an 1800 RPM machine.

The red thermometer icons indicate targets to compensate for thermal growth where used for this alignment.

The values to the right of the thermometer icons indicate vertical plane targets of +18 at the front feet of the blower and +14 at the front and back motor feet. No targets were entered for the horizontal plane.

The report shows all necessary information on a single page.

About the Author

Mike Keohane has been involved in machinery reliability since 1985. He started as a field service engineer for IRD Mechanalysis. Prior to that he was a wireline logger for Schlumberger Well Services. He joined VibrAlign in 1992 and supports clients in Georgia, South Carolina, Alabama and the Florida Panhandle. In addition to precision alignment, he has field experience in vibration analysis, field and shop balancing, oil analysis and ultrasonics. Mike holds a BSME from Michigan State University. Mike and his wife and two children currently live in Peachtree City, GA.

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