LINEAR VIBRATION GUIDELINES

LINEAR VIBRATION (cont) - TM-55-1930-209-14P-9-4_146

TM-55-1930-209-14P-9-4 Water Purification Barges (NSN 1930-01-234-2165) Electric Power System Manual
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LINEAR VIBRATION TESTING AND ADJUSTING Balance Procedure The following correction procedure applied to 1st order vibration motion. 1. The crankshaft must assume the same position each time a balance adjustment is made. To assure this identical location is assumed, position flywheel to top dead center (TDC) of Number 1 cylinder. A chalk mark or scribe across flywheel and coupling plates will provide an easy reference during the balancing operation. 2. Remove bolts holding generator coupling plates to flywheel. Rotate generator rotor with plates attached 90° clockwise while flywheel remains at Number 1 TDC. Replace coupling plate bolts and retest for vibration. 3. If vibration remains, again position flywheel at TDC Number 1 cylinder, index generator rotor another 90 clockwise (total 1800), and retest. 4. If necessary, repeat Step 3 by rotating another 90° clockwise. 5. Position coupling assembly relative to flywheel where least amount of vibration occurred. If magnitude of vibration remains unacceptable, add weight of 2 oz (56.70 g) under any single coupling plate to flywheel bolt. Flat washers can be used for this purpose. Bolt must be sufficiently long to maintain at least 1 1/4 times the bolt diameter of thread engagement. 6. Observe vibration level and relocate weight 90 quadrant to identify where minimum vibration occurs. 7. Add additional weight at point of minimum vibration identified in Step 6 until vibration level is no longer diminished. In no case should more than 5 oz (141.75 g) be added under any one bolt. 8. If vibration levels are still unacceptable, a local vibration control specialist should be consulted. LINEAR VIBRATION GUIDELINES The following graph is for use with analyzed linear vibration motion. The graph tables apply to measurements made an the basic engine structure and generator frame. It is not for component vibration. Figure 8 Line A is to be as a guideline for units as installed, either with or without mounting isolators. If the linear vibration motion is at higher levels, vibration complaints may occur from personnel discomfort and perhaps some premature parts service. Line B is the vibration motion limit expected on a bare engine, i.e., with all crankshaft-driven equipment removed, and the engine mounted on isolating mounts where the mounted engine natural frequency is less than one-half the exciting frequency. 107

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