Thermal Growth and
Movement Studies

Good machine train shaft alignment depends on accurate thermal growth and movement data. Typical O.E.M. target alignments specifications are generally based on thermal calculations for a generic package. Actual thermal growths and movements can vary greatly from installation to installation. A movement study performed on an individual machine identifies the actual movement from a cold non-running condition to a hot running condition. Based on this data, the ideal cold shaft alignment is identified and substituted for the generic O.E. M. recommended alignment.

Tern Technologies utilizes a full spectrum of optical and laser measurement tools in order to tailor each individual survey to the customers specific needs. Depending upon the machines and measurements desired, one system or another may be best suited for the project. In other cases a combination of both optical and laser tools may offer the best results.

Optical Transit for horizontal data” “Optical scale and dowel pin data point on bearing housing

In an optical survey, reference points are installed on the machine cases, bearing housings or other points of interest. A precise optical survey is conducted to measure each individual data points location referenced to vertical and horizontal benchmarks installed in the foundation, support structure, main building supports or other suitable reference points. Data from a cold survey is compared to corresponding data from a hot survey. The movement observed is used to identify the ideal cold shaft alignment position. The same optical measurement techniques may also be applied to movement surveys for other purposes such as foundation movement or settling, or piping movement.

Tern Technologies, Inc. performs laser measurement surveys using the Permalign laser system manufactured in Germany by Pruftechnik AG, and distributed in the USA by Ludeca, Inc., in Miami, Florida. (Link to Ludeca Website) This system is designed to use two laser emitter/receiver heads and two 90 degree roof prisms. The laser emitter/receiver interfaces with an IBM compatible computer system. With appropriate software, movement data is downloaded and stored to the computer. The two laser emitter/receivers are mounted on one machine on one side of the coupling, and the prisms are mounted on the other machine on the opposite side of the coupling.

One laser/prism pair is mounted in the vertical orientation and one is mounted in a horizontal orientation. The vertical laser measures vertical offset and horizontal angle changes. The horizontal laser measures horizontal offset and vertical angle changes. The computer software interprets that laser emitter/receiver as stationary, and shows prism movement relative to the laser head.

The Permalign laser system may also be adapted to measurement surveys other than alignments across a coupling. These surveys may employ the 90 degree roof prism mentioned above or may be designed for another type of reflector called a triple prism. Other surveys may be to monitor piping induced movement and/or casing and bearing housing movement.

(See Case History #2)

Both the optical and laser measurement methods have their strong points and weak points. Tern Technologies, inc. maintains an extensive equipment inventory of both optical and laser measurement tools. Our highly trained personnel apply the right tool to the right job. Our expertise, experience and inventory allow us to tailor each individual job to satisfy the customer’s needs, and solve the alignment problems that are present.

All data is presented in a clear and concise reporting format. Recommended alignments can be expressed graphically, as dial indicator readings or as values for use with any of the Pruftechnik laser tools.

The following page is a sample alignment drawing based on optical thermal growth data. It shows a graphic representation of the thermal growth observed with the resultant projected hot running misalignment.

Insert Drawing from Jeff