Traditionally, maintenance departments do not sing their own praises, but maybe that should change. In many companies maintenance departments are still considered as an overhead, a cost of doing business. They don’t see that improved maintenance procedures can improve a company’s bottom line — by reducing the energy bill, for instance.
As an example, Lake Erie Steel, a large steel mill in Nanticoke, Ont., recently bought a dual-beam laser shaft alignment system, in this case, an Easy Laser unit. This system gives it the ability to align the long jack shafts that are used on its water cooling towers.
The procedure for this type of system is to measure each coupling at each end of the jack shaft, then use both sets of alignment results to calculate the necessary correction in order to align the machine units.
These shafts are 4.3 m (14 ft) in length, which is not a problem for the laser system, as it can measure shaft alignment over a distance of 18 m (60 ft). In the past, a contractor had done this work using a single-beam system that could not span the necessary distance of 4.6 m (15 ft) in order to measure directly from the motor shaft to the gearbox shaft.
In using the new system, Lake Erie Steel’s maintenance foreman, Cliff Dosser, and his crew started an alignment of a jack shaft by mounting one laser detector on the motor shaft and another on the gearbox shaft. This means they were doing true shaft-to-shaft alignment. Then by simply using the laser beams that were centred in the closed target at the 9 o’clock position, the shaft was then rotated to the 3 o’clock position.
This is a very quick and easy procedure that is used when doing rough alignment for jack shafts. It shows immediately if the machine is out of alignment and which way it has to move to correct the problem. In this case, it showed that the jack was grossly out of alignment, so the corrective work began.
With the laser target doors open, measurements were recorded in as little as 40 degrees of shaft rotation. The system display showed live time readings in both the horizontal and vertical planes for the moveable machine. This is usually the motor, however you can change the configuration of the machine units in the laser display. You can choose to move the gearbox if you wish, or one pair of feet from the motor and one pair from the gearbox. It’s your choice.
In this case, the trick was to choose the correction that required the least amount of movement. Then all that was needed was to reposition the machine, but the real skill necessary was in controlling the movement. At a distance of 15 feet, you don’t bump anything; it’s a gradual move that is best done with jacking bolts. The work was completed and unit put back in service
Dosser had an amperage reading taken on the machine unit before the realignment work was done and it showed a draw of 174 amps. After the work was completed, another reading was taken, showing 155 amps. That’s a whopping 19-amp drop!
Although Lake Erie Steel is running almost 24/7, it was estimated that the cooling tower ran half the year. That’s 4,380 hours, so that 19-amp drop works out to a little over a 10% reduction, which means 78,735 kWh is saved. Using an average of 0.07 cents per kW, that’s a saving of $5,511 per year.
I think Dosser and his crew should be quite pleased with themselves because if you look at this another way, not only have they reduced the plant’s overall carbon footprint by taking 54 metric tons of CO2 out of the environment (that’s like removing 8.2 cars off the road), they have also done an excellent job of realigning the motor and gearbox, which means that barring unforeseen circumstances, the plant will get the optimum life for this machine set/cooling tower. I’d say that was a good day’s work, wouldn’t you?
John Lambert is the principal of Benchmark Maintenance Services Inc., Pickering, Ont. He can be reached at 905-509-6522, by e-mail at email@example.com, or visit www.withinspec.com.