LANTERN BRACKET PUMPS FOR AN EASY PUMP AND MOTOR ALIGNMENT

Pump shaft and motor shaft alignment is very important for long useful equipment life, and to extend the running time between repairs.

When mounting the pump and motor on the common baseplate, the two shafts, pump and motor, are always aligned, but it is still possible that during transport and/or when anchoring the pump on the system the two shafts are no longer aligned.

Excessive misalignment can have undesirable consequences. These include internal rubs, excessive vibration, increased static and cyclical stress.

These factors can lead to premature failure of bearing, seals, couplings and other parts.

Before proceeding with the commissioning of the pump, it is necessary to check the motor-shaft alignment.

on’t use a flexible coupling to compensate for misalignment between the pump and motor shafts.

The purpose of the flexible coupling is to compensate for temperature changes and to permit some axial movement of the shafts without interference, while they transfer energy from the motor to the pump.

For pumps on base, remove the coupling protection and, using a thickness gauge or comparator check the angular alignment, then make sure that the distance between the semi-couplings is the same along the whole periphery.

Then check the parallel alignment with a ruler or comparator.

The unit is aligned when the distance between each shaft and the ruler, resting on the coupling, is the same on four diametrically opposite points.

Don’t use a flexible coupling to compensate for misalignment between the pump and motor shafts. The purpose of the flexible coupling is to compensate for temperature changes and to permit some axial movement of the shafts without interference, while they transfer energy from the motor to the pump.

If an excessive deviation is found, first remove the pipes and loosen the fixing screws of the base.

If the coupling returns aligned, shim the base plate and reassemble the pipes.

For any further corrections, loosen or take off the screws, where required, in order to move the feet on the base and, if it is necessary, fit additional calibrated sheets or washers.

The alignment procedure should be repeated at various intervals to identify installation errors and compensate for equipment operation.

This is the way to assure long equipment life. It is recommended to go through the alignment procedure and make corrections in the following stages:

1. At Pump Installation: Be sure the motor shaft centerline is below the pump shaft centerline so that it can be shimmed upward.
2. After connecting the piping and accessories: Before starting the pump, repeat the procedure after all associated connections have been made.  
3. Hot alignment: Allow the equipment to run for three or four hours and come up to operating temperature, then shut-off the pump and repeat the alignment procedure with the equipment hot.
4. Running alignment: after the pump has been running for a week or ten days, perform an alignment check to verify that the equipment is not suffering pipe strain or binding from thermal growth.

Alignment is a time-consuming operation and must be carried out periodically, and in any event always after removing the pump or motor from the base.

 The alignment procedure should be repeated at various intervals to identify installation errors and compensate for equipment operation.

This is the way to assure long equipment life.

In order to eliminate all problems related to the alignment of the coupling and problems caused by incorrect installation, SR proposes a pump-motor coupling system by means of a cast-iron lantern which correctly positions the motor and its shaft.

The coupling of the lantern flange with the motor flange ensures that the coupling is always radially and angularly aligned.

This not only ensures a longer service life of the coupling's rubber elements, but also requires no further checking of the coupling's alignment.

Furthermore, with the same robustness provided by the oil-lubricated bearings, the pump is more compact and easier to handle.