Marine Engineering

There are three shaft alignment procedure or methods currently used to calculate the amount of shim changes and horizontal moves required to achieve accurate machine alignment. They are each capable of arriving at the same results by use of mathematical formulas and/or graphical solutions. There are various tools that are available to help in the process. The first is a simple pocket calculator. With the proper formula and a basic understanding of the alignment process, accurate machinery movement can be achieved. The second method available is the graphical solution. This method uses a simple 10 x 10 piece of graph paper that gives a pictorial representation of the machines and the amount of movement needed to correct the misalignment. The third method is the use of a computer, either a desktop or a special computer designed specifically for the alignment task. We mentioned the computer method only to make you aware of its existence.  The following are the methods of alignme...

If the base plate has jackbolts installed, the task of moving the machine is made much easier. In many situations, it is best to have jack screws installed at the time of the alignment rather than trying to move the machine some other way, which is often more difficult and requires more time. Before any of the hold-down bolts are loosened, all of the jackbolts must be loosened on the machine. Any unequal pressure of the jackbolts could result in an uncontrolled move and require the technician to take another set of alignment readings.  When loosening the hold-down bolts, back them off just enough to allow the machine to slide sideways. Since it takes very little pressure on the jackbolt to move the machine horizontally, there is no real need to completely back off or remove the hold-down fasteners.  If a graph is constructed determining the position of the misaligned shaft, you will know exactly which direction to move the machine. Another way to avoid confusion is to alwa...

As with all vertical moves, using a dial indicator is not necessary to determine the change in the vertical direction, but it can be helpful to check for any soft foot created when moving the machine.  By using a micrometer, the exact thickness of the shims being installed can be determined for the required alignment correction. Be sure to measure every shim that is installed. Do not believe what is printed, stamped, or etched on the shim. Always check the shim to be sure.  When loosening the hold-down bolts, the first precaution is to loosen only two bolts at a time when making any shim change. If you loosen all the hold-down bolts at the same time and then raise the machine, the entire configuration at the feet may change. This is particularly true if any of the feet have been corrected for soft foot conditions using a tapered or step shim.  Leaving two hold-down bolts tight reduces the chances of an uncontrolled move. Any uncontrolled movement of the machine...

Types of shaft alignment methods: Visual Line-Up Straightedge/Feeler Gauge Rim and Face Cross Dial Reverse Dial Laser Visual Line-Up The visual line-up method is the most common method of alignment. Used in initial installations, visual line-up allows technicians to analyze the working conditions and feasibility of installation. Straightedge/Feeler Gauge Straightedges are used to determine the offset between coupling halves. Corrections are made under all four of the machines feet. Feeler gauges or taper gauges measure the gap between coupling halves at the bottom and top of the coupling. Rim and Face This method is similar in principle to using a straightedge and feeler gauge, but more accurate since dial indicators are used. The rim reading measures the offset between the coupling halves. The face reading measures the angular difference between the faces of the coupling. Changes are calculated with the same formula as the straightedge/feeler gauge met...