Categories: Shaft Alignment,Geometric Measurement,Machinery Maintenance,Other Topics

Compressor Rod Runout with the NXA Runout Probe

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By on September 27, 2018

The Fixturlaser NXA Runout Probe was introduced last year as an accessory to the Fixturlaser NXA Pro and Ultimate alignment tools.  As originally envisioned, the runout probe was designed with shaft and coupling runout measurements, and direct soft foot measurements in mind.

The Runout Probe provides a digital linear displacement measurement, much like a dial indicator, but with the added benefit of electronic documentation through the Bluetooth connection with the NXA Display Unit.  Naturally, additional uses for the runout probe were discovered, since just about any measurement currently done with dials can be performed using this tool.  In this article, one of those uses is highlighted and discussed, compressor rod runout.

In many large frame reciprocating compressors, rod runout is an important routine maintenance check as a measure of potential machine wear and installation integrity.  Specifically, many of our customers complete these checks on Ariel Compressors who explicitly calls for rod runout checks as a suggested (or required) maintenance task according to a schedule of hours or months of service life.

The Runout Probe replaces the dial indicator method of making rod runout measurements. Users have expressed several advantages to the Runout Probe method.

First, setup is easier because the Runout Probe has a long travel and is narrow making the task of positioning inside a small space simple.

Second, the NXA Runout Probe is electronically zeroed, meaning there is no need to use a mirror to set dial zero to begin.

Third, reading the runout is viewed on the NXA display unit; again, eliminating the need for mirrors and the possibility for missing a negative/positive swing on a dial mounted inside a tight space with limited viewing angle.

Finally, and perhaps most importantly, the Runout Probe program in the NXA Display Unit records the measurement (electronically) for a more complete documentation of the completed maintenance check.

Multiple runout probes can be linked simultaneously to the display unit, which also means both X and Y directions can be checked on one head at the same time to limit the number crankshaft rotations required to measure the complete machine (depends on number of throws).

Similarly, the Runout Probe can be used for crankshaft web deflection measurements – more on this in another article.

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