Dynamic movements when aligning critical equipment needs more attention

Dynamic changes in the rotating machinery from an Off Line to Running condition, needs more attention. There is no such thing as identical" machines having identical dynamic movements. One cannot ignore the possibility of horizontal movement, assuming growth will be symmetrical and only accounting for the thermal effects.

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.

Fixturlasers 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 have, through extensive tests, showed that in addition to
cold alignments, the actual dynamic movements of machinery need to be
considered when aligning.

For further information contact
www.fixturlaser.com
Peter Sandström Manager Application Engineering
E-mail: peter.sandstrom@fixturlaser.se
peter.sandstrom@fixturlaser.se
phone +46 31706 28 08
You can also request a copy of the white paper"
where a number of case stories are presented and other technical
information from Hans Hilmersson
hans.hilmersson@fixturlaser.se
or phone +46 31 706 28 07