Alignment of Two-Bearing Generators{4471} Caterpillar

Engine: All 3600 All C280 All G3600

Introduction

This Special Instruction explains the alignment procedure for 3600 engines with two-bearing generators. Do not start the alignment procedure until the electric set is permanently installed. If the generator set is moved to a different location, check the alignment and make any corrections necessary. Alignment between the generator and the engine must be correct to get the maximum performance and the longest life from the generator set. Refer to Illustration 1 in order to view the different parameters for alignment.

Procedure For Alignment

1. Review the components of the complete installation. When the weight of any attachment or fluid compartment exceeds 225 kg (500 lb), fill the compartment or simulate the weight of the fluid before you proceed with the alignment.

2. Attach the isolators to the base. The clearance between the floor and the bottom of the base should be at least 25.4 mm (1.00 inch).

   Level the isolators. Refer to Special Instruction, SEHS9162 for details on the procedure.

3. The end play of the crankshaft should be 0.4 ± 0.2 mm (0.016 ± 0.008 inch). The inspection of the end play of both the crankshaft and the generator shaft must be performed. This inspection will ensure that the thrust bearings for the generator and the engine bearings are not damaged during operation.

   Note: In order to protect the bearings against damage, prelube the engine and the generator before rotation.

   In order to protect the generator bearings from damage, lubricate the generator bearings before any axial movement. Also lubricate the shafts before the shafts are turned. If the generator is not equipped with a pump for prelube, drain the oil from the bearing into a clean container. Replace the drain plug. Refill the bearing with the oil from the top. This procedure will provide the prelube that is needed to turn the shaft.

   Check the end play of the crankshaft by attaching a dial indicator to the engine block or a stationary surface. Clean the surface of the following materials: grease, dirt and protectant. The reading can be taken in one of two areas. In order to gain access to the first area, remove a side cover from the engine block. Install the indicator rod against the crankshaft at the counterweight or some other suitable location on the crank. For the second area, install the indicator rod against the flywheel at the rear of the engine. Avoid the flexible part of the coupling.

   Use a clean pry bar against the crankshaft in order to move the crankshaft back and forth. The crankshaft may be difficult to move. If necessary, prelube the crankshaft in order to reduce the force that is required to move the crankshaft. Repeat the measurements several times in order to verify the results.

   Note: Never pry on the damper in order to check the end play of the crankshaft.

4. The split flange will not be installed for rough alignment. Install two alignment bolts at an angle of 180 degrees between the drive flange for the generator and the adapter. (Do not install the nuts.)

   The two alignment bolts will allow the generator shaft and the crankshaft to rotate. Therefore, only the misalignment will be measured.

Different alignment methods:

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Illustration 1	g00565566
(1) Face gap (top) (2) Diameter gap (top) (3) Face or angular misalignment (4) Bore or parallel misalignment (5) Face gap (bottom) (6) Diameter gap (bottom) (A) Face Alignment (B) Bore Misalignment

1. Laser alignment:

   Note: The laser alignment tools typically measure the actual offsets. The dial indicators measure a total indicator reading (TIR).

   Follow the instructions provided by the manufacturer in order to ensure that the parallel misalignment and the angular misalignment are within the specifications.

   Typically, the laser alignment tools compensate for any axial movement of the rotor shaft for the generator or the crankshaft. If the axial shaft moves during the angular measurements, consult the literature on the laser alignment tool for information.

2. Dial indicators:

   If laser alignment tools are not available, the use of dial indicators is acceptable for alignment. Use the dial indicator with caution because the following problems will result: the interpretation of measurements, the compensation of the movement of the axial shaft and the proper support.

   Use the following procedure to operate the dial indicator:

   1. Attach a rigid bracket to the hub for the generator in order to support both of the indicators. Attach one indicator and read the angular misalignment of the flywheel at the 12 o'clock position. The indicator "A" is shown in illustration 2. Attach the second indicator "B" and read the parallel misalignment at the 12 o'clock position.
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   Illustration 2	g00565584
   (7) Rigid Bracket (8) Generator (9) Crankshaft (10) Indicator (7H1942 or equivalent) (A) Indicator (B) Indicator (C) Indicator

   2. During crankshaft rotation, the rotor will extend beyond the flywheel due to the clearance between the two loose alignment bolts and the holes. Rotate the flywheel clockwise until the rotor starts to turn. This action will determine if the rotation will have a detrimental effect on the measurements. Then set indicator "A" and indicator "B" to zero. Now, rotate the flywheel counterclockwise until the rotor starts to turn. If either indicator records more than a 0.051 mm (0.0020 inch) change in this short radial distance that was traveled, then place a chalk mark on the flywheel close to the location of the indicator "A". Always move the flywheel until the flywheel lines up with the chalk mark. Perform this rotation before you set the indicators to zero. Rotate the flywheel before you measure at the 3 o'clock, the 6 o'clock, and the 9 o'clock positions.

      Note: The equipment should be at ambient temperature for the initial cold alignment procedure. The engine will have a larger thermal expansion than the thermal expansion of the generator. The thermal expansion is accounted for in the specifications listed in the ""Alignment Data Sheets" ".

      At the 12 o'clock position, set the dial indicators to zero. Rotate the engine and rotate the generator in the direction of operation. Record the readings at the 3 o'clock, the 6 o'clock, and the 9 o'clock positions. Continue to rotate the engine to the 12 o'clock position in order to verify the repeatability.

      Whenever the generator is repositioned, the bezel on all four dial indicators must be reset to zero at the 12 o'clock position. Always zero the dial indicators at the 12 o'clock position before repeating the measurements. Repeat the measurements at the 3 o'clock, the 6 o'clock, and the 9 o'clock positions.

      The engine or the generator shaft may move axially during the rotation of the crankshaft. Since this movement is unavoidable, compensate for the movement in the angular measurements. In order to record a valid angular measurement, add the axial travel of the indicator "C" to the reading of the other indicator "A". Refer to illustration 2. The final result is the true value of the angular alignment.

Softfoot check:

1. Soft foot is measured with a dial indicator. Mount a dial indicator from the base assembly to the top of the foot next to the engine block. Be sure that all the jacking screws are loose. While one foot at a time is loosened, the deflection of the foot must not change more than 0.076 mm (0.0030 inch). If necessary, add shims in order to eliminate the soft foot. Repeat the procedure for the soft foot until all the feet are measured for compliance with specifications. If necessary, add shims under the feet in order to eliminate gaps. When possible, avoid using shims under the foot with the slider block. Do not trim the shims. The addition of shims is required in order to provide equal loading on each foot. This equalization prevents unnecessary stresses in the welds and the components.

2. Loosen the mounting bolts for the generator from one foot at a time. Check for gaps with a feeler gauge. If necessary, add shims under the feet in order to eliminate gaps. Shims must be added in order to provide equal loading on each foot. This equal loading prevents unnecessary stresses in the welds and in the components (soft foot). Torque the alignment bolts again. Refer to the generator mounting group for values of torque.

Split ring installation:

1. Check the positions of the crankshaft and the generator shaft. This verification will help to center the shafts during operation in the middle of the end play of the shafts. Position the crankshaft all the way forward toward the front of the base. Position the generator shaft toward the rear of the base against the thrust bearing. For generators without thrust bearings, the generator must be positioned in the magnetic center. Install the split ring spacer and check the gap that is left between the split ring and either the generator or the coupling. Take the previously recorded values for the end play of the crankshaft and the end play of the generator. Adjust the generator in order to set the gap. Set the gap to one half (50 percent) of the total end play of the generator and of the engine.

   Note: To reduce the effect coupling sag, measure with the feeler gauge at the 90 degree side and the 180 degree side of the coupling.

   For generators with an end play of less than 0.102 mm (0.0040 inch), the end play of the generator may be omitted from the above procedure. In this case, only centering of the crankshaft is necessary.

   During the operation of the engine, monitor the temperatures of the generator bearings. Compare the temperature to the limits specified by the generator manufacturer. If the temperatures are higher than the limits, repeat the procedure for centering the generator and the crankshaft.

2. After the alignment of the generator meets the specifications of the preliminary alignment, record the dimensions. Install the split ring spacer and torque the bolts to the specifications of the flexible coupling assembly.

Final alignment check:

1. A final check of the alignment must be performed in order to meet the specifications for the final alignment.

   For the specifications of the final alignment, the parallel misalignment for the vertical offset (12 o'clock to 6 o'clock) must be within 0.076 ± 0.076 mm (0.0029 ± 0.0029 inch). The parallel misalignment is measured as the bore with the indicator "B". The parallel misalignment for the horizontal offset (3 o'clock to 9 o'clock) must be within 0.000 ± 0.127 mm (0.0000 ± 0.0050 inch).

   Note: The equipment must be up to full operating temperature before you complete the final alignment. The alignment must be completed before the equipment cools off. Any cooling of the equipment will possibly give false alignment readings due to thermal contraction.

   For the specifications of the final alignment, the angular misalignment must be within 0.000 ± 0.102 mm (0.0000 ± 0.0040 inch) at the 6 o'clock position. Apply this tolerance to the values that are measured between the 3 o'clock position and the 9 o'clock position.

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Illustration 3	g00565623
(11) Edge of housing (12) Feeler Gauge (13) Housing (14) Generator (15) Notch (16) Rotor (A) Detail A

2. Assemble all the following assemblies: screens, the covers and the guards.

3. After the engine has reached operating temperatures, check the levels of vibration in the following locations:
   • the front of the engine (vertical and horizontal)

   • the rear end of the engine (vertical, horizontal, and axial)

   • the front of the generator (vertical and horizontal)

   • the rear of the generator (vertical, horizontal, and axial)

   The following limits of vibration are for the 3600 generator set applications:

   • Peak to peak displacement limit at 1/2 order frequency = 0.13 mm (5.0 mils)

   • Peak to peak displacement limit at the first order frequency = 0.13 mm (5.0 mils)

   • Overall displacement = 0.22 mm (8.5 mils)

   • Overall velocity = 34.3 mm/s (1.35 in/s)

   Levels of vibration in excess of these limits are an indication of possible misalignment or of an imbalance in the package. These issues must be addressed immediately.

   If the levels of vibration exceed the limits, consult the Caterpillar dealer, or consult the factory.

   Refer to the Caterpillar Engine Data Sheet, LEKQ4023 for additional information on the following items: linear measurements of vibration, limits and corrective actions.

4. After the generator set has run for 200 hours to 500 hours, check the alignment. If the alignment is not within the final specifications, realign the engine. Run the engine for 200 hours to 500 hours, and check the alignment again. Continue this procedure until the alignment is within the final specification. If the alignment is within the final specification, dowel the generator in accordance with the generator mounting group:
   • Drill the holes to a diameter of 25.37 ± 0.02 mm (0.9908 ± 0.0007 inch) and to a depth of 80 mm (3.15 inch).

   • Ream the holes to a diameter of 25.405 mm (1.0002 inch).

   • Assemble the dowels. The standard size 2W-2988 Dowel measures 25.405 mm (1.0002 inch). The oversize 4W-5222 Dowel measures 28.626 mm (1.1270 inch). The other oversize 4W-5223 Dowel measures 31.801 mm (1.2520 inch).

   Note: The engine and the generator must be doweled on the identical side in order to fix a single direction for thermal growth of the equipment.

Alignment Data Sheets

Crankshaft Deflection Data Sheet