Do you have the right alignment when installing your pumps?

The pump set can be aligned using either the:

1. Traditional Method
2. Laser Equipment

Traditional Alignment Method

The following equipment is needed for checking coupling alignment using the traditional method:

1. Gap gauge
2. Set of feeler gauges
3. Straight edge
4. Dial gauges

Prior to checking the alignment, isolate the power to the driver, remove the coupling guard and disconnect the coupling so that the pump and driver can be turned separately.

For the traditional method of checking coupling alignment the procedure involves the separate measurement of the angular and eccentric errors in both vertical and horizontal planes and correction made where needed.

This can be done in two ways:

1. The first allows a preliminary alignment check using a gap gauge, feeler gauges and a straight edge.
2. A second more accurate final check is done using dial gauges.

The preliminary check is normally done early in the installation process just to see if the alignment is reasonably correct while the final alignment check is carried out just after installation is complete before the pump set is first started.

Preliminary Alignment

Angular Alignment:

Errors of angular alignment should be corrected before attempting to eliminate eccentricity.

Place chalk marks on both coupling halves at points A & B above then rotate both half couplings together and measure the gaps at points 1, 2, 3 & 4 above.

Parallel Alignment:

If this error is in the vertical plane, adjust the shims under the driver. If the error is in the horizontal plane, it is usually easily eliminated by moving the driver horizontally until the correct setting is obtained. Concentricity can be checked with a straight edge below:

Final Alignment

Angular Alignment:

Clamp two dial gauges to the coupling halves as shown in Fig 3 and zero the gauges.

Rotate both shafts through 180⁰ and note the gauge readings. If the readings are the same, not necessarily zero, the angular alignment in the vertical plane is correct.

Rotate both shafts through a further 90⁰ and note the gauge readings. If the readings are the same not necessarily zero, the angular alignment in the horizontal plane is correct.

The amount of correction at each point can thus be determined.

Where possible couplings should be aligned to + or – 0.25 mm, full indication movement on the dial gauge.

During this operation ensure that both shafts are pushed against their axial locations.

Parallel Alignment:

A dial gauge is mounted on the coupling as shown below. Again chalk marks should be made on both coupling halves as shown for the preliminary parallel alignment. Slight variations in the diameter of the two halves can be checked using a straight edge and a feeler gauge equal to half the difference in concentricity.

When a dial indicator is used, as above, any sag which may occur in the aligning equipment must be measured and compensated for in the coupling alignment.

The alignment of the pump and driver is now complete, and the coupling can be connected, coupling guard reinstalled and the power reconnected.

Laser Alignment Method

Laser alignment has a number of benefits over the traditional method as follows:

• Has accuracy to 1 micron.
• 180 degrees rotation minimum.
• All data is stored internally on the equipment.
• Movement requirements are calculated and shown by the equipment.
• Soft foot function on the equipment can check for soft foot.
• Thermal expansion can be accommodated.

The following is a simple summary of how laser alignment is carried out, however, as there are many brands of equipment available, the manufacturers’ instructions should be followed for the equipment being used:

N.B. For this method it is not normally necessary to disconnect the coupling.

Step 1 – Mount the laser on the part of the machine which will not be moved during the alignment process, normally the pump. The receiver/reflector is mounted on the part of the machine which will be moved, as shown in Fig. 5 below:

Step 2 – Connect the laser computer into the system as mounted.

Step 3 – Centre the laser beam at the centre of the reflector, see Fig. 6.

Step 4 – The laser system is now ready to record the alignment of the pump set. Rotate the shaft as per the laser system makers’ instruction to a record point, record the readings. Repeat for the number of record points required to determine the alignment of the pump set.

Step 5 – After completion of Step 4 the computer will show the angular and parallel misalignment of the pump set with how far the moveable machine has to be raised or lowered and/or moved sideways.

Step 6 – Adjust the moveable machine in accordance with the instructions given by the computer in step five.

Step 7 – Re-centre the laser beam and repeat the process to check that the alignment is within the required tolerance for the particular pump set being aligned.

The following is a guideline for alignment tolerances for various coupling types and shaft speeds which are generally the factors which dictate the tolerance:

N.B., From this table, 1 mil is equal to 1 thousandth of an inch

N.B., The tolerance for soft foot throughout the speed range is 0.06 mm/2.0mils

Coupling Alignment Summary

Once the alignment check is complete, particularly if adjustments are made, the pump and driver bolts should be tightened down on the base and the alignment rechecked.

Belt-driven pumps:

It is important that the driving and driven belt pulleys are in the same plane as and parallel to each other as shown below:

While some pumps have bearing housing assemblies designed for belt loads, the majority are not. When belt-driven pumps are used to prevent excessive loads being placed on the pump bearings, a jack shaft is used with pulleys mounted between two bearings and connected to the pump or motor by a flexible coupling. This illustration depicts an electric motor capable of carrying belt loads.

In this case, the jack shaft arrangement should be aligned to the motor or pump as you would align a pump and motor, and the two pulleys aligned as shown in Fig. 7.

Summary

This article concludes the series on; pump installation with how to check the pump alignment such that the pump set is fully installed ready for operation. Following the methods outlined in this series will ensure that the pump set is correctly installed and will operate successfully during its working life.