Guidelines for Inspection of the 303-8189 Flexible Coupling Gp {3252, 4450} Caterpillar

Engine:

3512C (S/N: SLM1-UP)

Generator Set:

3516B (S/N: PBR1-UP)

3516C (S/N: SBJ1-UP; SBK1-UP; SBM1-UP)

C175-16 (S/N: WYB1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you have read the instruction and until you understand all of the instruction.

This Special Instruction is to provide a basic understanding of the inspection and serviceability of the 303-8189 Flexible Coupling Gp .

General Description

Illustration 1	g01874779
303-8189 Flexible Coupling Gp (1) Coupling assembly (2) Cover plate (3) Silicone blocks (4) Inner member (5) Outer member

A coupling with serviceable silicone blocks is used to transmit power from the engine to the generator.

Illustration 2	g01874791
The rotation is clockwise. (3a) Leading block (3b) Trailing block

The power is transmitted through the leading blocks. The leading blocks are constantly under compression while the engine and the generator are running. The trailing blocks are not under compression and may rotate during engine operation. The two types of blocks will wear differently.

Inspection Schedule

To ensure the reliable operation of the engine and generator, inspect the coupling during the engine top end overhaul. The overhaul schedule is defined in the Operation and Maintenance Manual. If the coupling shows excessive wear at the inspection, replace the entire coupling. If the the silicone blocks show excessive wear at the inspection, replace the silicone blocks. If the blocks are replaced, then all 24 blocks need to be replaced as a complete set.

Inspection of the Coupling

In order to inspect the coupling, the generator must be removed from the engine. Remove the cover between the engine and the coupling. Remove the bolts from the coupling on the flywheel. Move the generator away from the engine. Attach a proper lifting device on the coupling. The coupling weighs 164 kg (362 lb). Unbolt the coupling from the generator and remove the coupling. Place the coupling on a flat surface. Remove the cover plate.

Illustration 3	g01874820
Coupling with the cover plate removed

Note: The blocks must remain in the original sequence in the coupling. If the original sequence is changed, shorter coupling life may occur due to uneven loading of the blocks.

Mark the silicone blocks as the blocks are removed in order to keep track of the original position of the blocks. Clean the blocks and clean the cavities in the coupling with 5N-5561 Silicone Lubricant . The silicone lubricant can be used in small quantities to aid in the assembly of the coupling. Do not use a petroleum based agent. After the inspection is complete, assemble the coupling. Install the coupling on the generator. Align and install the generator on the engine.

Refer to the Special Instruction, SEHS7654, "Alignment – General Instructions" and Special Instruction, REHS0177, "Alignment of the Close Coupled Two Bearing Generators" for instructions on the generator alignment.

Inspection Criteria

The illustrations 4 through 6 give examples of normal coupling wear.

Illustration 4	g01874997
Normal wear on the inner member

Illustration 5	g01875013
Normal wear on the inner member and outer member

Illustration 6	g01875014
Excessive amount of silicone lubricant

An excessive amount of silicone fluid was used during the field assembly of the coupling shown in illustration 6. The textured pattern was created by dust particles collected in the coupling. No harm has occurred to the coupling.

The illustrations 7 through 12 give examples of normal coupling block wear.

Illustration 7	g01875016
Normal discoloration

It is normal for the blocks to discolor from blue to gray or black. The discoloration does not indicate that the blocks have been overloaded or that the blocks have suffered excessive wear.

Illustration 8	g01875017
Normal discoloration

Illustration 9	g01875018
The difference in wear patterns between leading blocks and trailing blocks

In illustration 9, the left hand block is a trailing block and the right hand block is a leading block. The leading block will always have a larger, more pronounced imprint from the coupling because it is compressed more and has a larger contact area with the metal.

Illustration 10	g01875019
Trailing block

Illustration 11	g01875020
Leading block

Illustration 12	g01875021
Leading block that was turned during inspection

The illustrations 13 and 14 give examples of wear on the inner member and on the cover plate.

Illustration 13	g01875023
Wear on the inner member caused by contact with the cover plate

Illustration 14	g01875025
Cover plate

Wear on the metal parts of the coupling may be caused by the generator shaft position. The position of the shaft is not a significant problem. Testing has shown that operating with this slight interference has little impact on the vibration levels. Ensure that the generator shaft is centered axially prior to installation of the coupling. Adjust the shaft position by pushing, pulling, or prying on the generator hub. Never pry on the generator fan or on the exciter.

The illustrations 15 and 16 give examples of blocks that are damaged and need to be replaced.

Illustration 15	g01875033
Block with deterioration

Illustration 16	g01875035
Block with deterioration

If 12 or more of the blocks have begun to crack as shown in illustrations 15 and 16, replace all 24 of the blocks.