October 8, 2011
By Stan Riddle
A machine train alignment, one in which there are more than two machine components, and more than one coupling, may seem difficult to most aligners. But with some basic understanding, and the ability to “see the forest as well as the trees,” a machine train alignment can be performed accurately and quickly.
We recently helped a customer who had been working unsuccessfully for two weeks to align a three machine train. With their newly acquired Fixturlaser XA Pro Machine Train program, and a little training, this job was completed in just over two hours.
First, careful measurements of all machine dimensions—distance between machine feet and distances to coupling centers—must be taken. If using the XA Pro Machine Train program, all of these dimensions can be put into one alignment file, and your XA can do all of the graphing for you. Or, it can be done on graph paper.
In this example, there was a steam turbine, coupled to a gear reducer, which was coupled to a center-hung fan. Measurements were taken between the turbine and gearbox, then between the gearbox and fan. In each measurement, the moveable machine was on the left, and the stationary machine was on the right. For simplicity, we will concentrate on the vertical correction only.
A graphical representation requires some experience in determining which feet to move. In addition, some machines may not move at all. In this case, the turbine had rigid piping, which allowed for only a slight movement, and the fan could not be lowered, or a rub would be induced in the fan housing.
They could lock the position of the turbine feet, and see how much movement would be required on the gearbox and fan.
The fan could not be moved up almost 3/8” or a rub would be induced in the fan housing.
The piping to the steam turbine would not allow it to be moved up 0.197” without major piping re-work.
Or, they could lock the position of the gearbox feet, and see how much movement would be required on the gearbox and fan.
They could also make rough adjustments to each machine position, and then do the alignment as two separate machines—aligning the gearbox to the fan, and then aligning the turbine to the gearbox. In the end, a combination of both was used, and below are the final alignment values. The XA Pro Machine Train program gave the customer the flexibility to look at numerous options, and make the best choice.
The gearbox was lowered by 0.075”, and all dimensions were re-measured. The alignment was completed between the turbine and gearbox. Then, the alignment was completed between the gearbox and fan.
Options – a good thing to have when performing a machine train alignment! They help turn an unsuccessful two week alignment into a successful two hour alignment.
For more information, contact us at www.vibradev.wpengine.com