BUSHING 2125712 - Caterpillar

D353 (46B, 47B);
G353 (64B);
D375 (43B);
D379 (68B, 76B);
G379 (72B);
D397 (41B);
D398 (66B, 75B);
G398 (73B);
D399 (35B);
G399 (49C);
3508 (23Z, 70Z, 1ZF);
3512 (24Z, 67Z, 3YF);
3516 (25Z, 73Z, 4XF, 5SJ)Introduction
This instruction shows the procedure for the cold alignment of two bearing generators to the above engines mounted on Caterpillar bases and using a Caterpillar viscous dampened coupling. This alignment procedure covers both generators driven from the flywheel (rear driven) and generators driven from the front of the engine crankshaft (front driven). Comments on special alignment situations (such as generator-to-generator driven, compound engines, the use of bases and couplings not manufactured by Caterpillar, etc.) are given on page 6.Do not start the final alignment of the generator(s) until the base is in its permanent position, the engine(s) permanently installed on the base, and the initial alignment of the generator has been completed.General Information
Cold Alignment
The cold alignment procedure described in this instruction is the recommended procedure for alignment of two-bearing generators to Caterpillar diesel engines. This procedure must be performed with all components at ambient temperature.In order to achieve correct operating alignment, the following factors have been taken into consideration in determining cold alignment specifications: 1. During the cold alignment procedure, the crankshaft lies at the bottom of its main bearing bores. Under running conditions, firing pressures, centrifugal forces and engine oil pressure all tend to lift the crankshaft and cause it to rotate around the center of the main bearing bores.2. The weight of the flywheel and coupling causes a small deflection of the shafts during the cold alignment procedure. 3. Engine heat causes the expansion of metal in the engine and generator during operation. The result of this expansion is a change in the locations of the centerlines of the crankshaft and generator shaft. Because the thermal expansion of the engine is greater than that of the generator, the change in the location of the horizontal centerline of the engine crankshaft will be greater than the change in location of the horizontal centerline of the generator shaft.Because of the above factors, the cold alignment procedure positions the horizontal centerline of the generator shaft above the horizontal centerline of the crankshaft. Alignment of two-bearing generators using the cold alignment specifications on page 24 will result in correct alignment during operation.Hot Alignment
In the past, a hot alignment check may have been used to check the accuracy of the cold alignment procedure. However, factory tests have shown that the results of the hot alignment check are inconsistent; therefore, this procedure is not recommended.Indicator Readings
When taking indicator readings, always remember that a plus (+) reading means that the tip of the indicator moved into the dial indicator; a minus (-) reading means that the tip of the indicator moved out of the dial indicator.When comparing two plus (+) indicator readings, the larger numerical reading is more than the smaller numerical reading. However, when comparing two minus (-) indicator readings, the larger numerical reading is less than the smaller numerical reading. In both cases, the indicator reading becomes less