Hot-Cold-Hot Alignment

The Challenge

A major Caribbean power company contacted Cascade MVS after experiencing failures on two of its gas turbine-driven gearboxes.

The Cascade MVS Solution: The Hot-Cold-Hot (H-C-H) system

The Cascade MVS Hot-Cold-Hot (H-C-H) system was developed by Ivo Dabelic in 1985 as a unique solution for a suspected gearbox deflection onboard VLCC “Exxon North Slope.” Since then, the system has been simplified and is now applicable to most “off-the-shelf” multi-channel vibration analyzers. Designed to be installed in running machines, it represents a revolution in “hot-to-cold” condition measurement.

As the power company’s gearbox was of welded construction, Cascade MVS was suspicious that the gearbox was warping and/or growing in unpredicted manner. The Cascade MVS H-C-H system was applied to all four corners (see pic below) as well as to Bull Gear bearing housing.

Cascade MVS Alignment

Data samples:

Hot Cold Hot Alignment Data

The Final Result

The linear growth at all measured points was recorded and the suspected warping was eliminated as the cause of the experienced gearbox failures. The Cascade MVS finite element modeling and vibration analysis was essential in solving the low-run failures.

Cascade MVS has used the H-C-H system in a number of gas turbine alignments. Our Hot-Cold-Hot Alignment PDF details two separate case studies where our H-C-H system has been successful in the diagnosis and correction of misalignment.

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