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Shaft alignment in critical machinery

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DYNAMIC changes in rotating machinery from an off line to running condition, need more attention, according to Fixturlaser (represented by Vitech ), who says there is no such thing as "identical" machines having identical dynamic movements.

Shaft alignment has mostly been carried out in off-line operating conditions.

However, machine conditions change from the time they are off line to running under normal operating conditions. Some of these changes are due to process forces (fluid pressures, airflow, etc.).

The most notable of these changes is the change in the temperature of the machine bearings and supports.

Dynamic changes are difficult to calculate.

Two identical machines may show drastically different alignment changes from off line to running. Great care must be taken when calculating the changes in the alignment condition of machines.

Just because two machines appear identical and serve the same function does not ensure they will exhibit the same operational characteristics.

Several methods have been used to measure the changes in the shaft alignment of two or more machines.

Although widely used, "hot aligning machines", only measures changes in the shaft alignment due solely to the changes in the machines' temperature.

Discharge pressure, shaft torque, multiple machines operating in parallel, electrical loading of a generator, etc., can also play an important role in the change of the alignment condition from off line to running. The changes will mostly be seen in the horizontal plane, but could also affect the vertical alignment.

A machine that operates exposed to large changes in temperature could exhibit extreme changes in its shaft alignment as the temperature changes.

Coupled machines need to be set to cold alignment targets that will reflect the actual changes in the shaft alignment. This will lead to lower vibration levels, increased mean time between failures, decreased maintenance costs, and increased production.

Fixturlaser's extensive research into the problems of dynamic movement has resulted in a revolutionary new alignment method.

Fixturlaser OL2R off-line to running fixture combined with a Fixturlaser shaft alignment system makes it possible to measure dynamic movements on machines from hot to cold or vice versa.

Changes in machinery alignment are mirrored by changes in the alignment of the OL2R brackets. By measuring and documenting the initial position of the brackets the actual online changes in the alignment values can be measured when the machine is online under normal operating conditions.

Alignment costs are small compared to production loss, should critical machinery fail. Poor alignment is one of the leading contributors to premature rotating machinery failure, often as a result of too little attention being paid to dynamic movements.

Fixturlaser has, through extensive tests, shown that in addition to cold alignments, the actual dynamic movement of machinery needs to be considered when aligning.

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