Inspect Brush Block and Brushes and Remove Slip Ring Brush Debris

1 Safety Precautions

danger Electrocution Hazard High Voltage Present Use proper Lockout/Tagout procedures before servicing equipment

warning Potential for Equipment damage Using a vacuum hose near live electronic equipment may cause equipment damage due to static. make sure equipment is turned OFF prior to vacuuming.

notice The following items may cause problems with the slip rings: - Do not touch the tips of the slip ring. Skin oils contaminate the brush and reduce usable life and potentially create future failures. Do not file or clean the brush tips under any circumstances. - Tube/Transformer oil (and other oils) cause major current draw through the power rings and communication error on the signal rings. - Since brushes are spring-loaded to ensure constant contact with the slip ring during operation, when the block is removed, the springs relax forward, causing the brushes to protrude further from their holders; however, the brushes do not eject from the block. - If you are re-using a brush, make sure you install it in the same orientation as it was removed. The brush was seated/conditioned in that position. - Use neoprene or nitrile gloves to limit irritation and ingestion of metallic dust. Do not remove the gloves near an exposed slip ring; the powder inside the glove can contaminate the ring.

2 General Brush Cleaning

1. Slide out the gantry rear cover.

2. Remove the slip ring covers.

3. Use a HEPA vacuum cleaner to remove residual brush debris. Remove all debris from the brush blocks, brackets, slip rings, and slip ring covers.

   note: Properly seasoned tracks have a brownish-black lubricant on the ring. This patina of carbon/silver is 0.002 - 0.003 mm thick and self-renewing. Do Not remove this film of lubricant.

4. As you vacuum, visually inspect all slip ring tracks for pitting or deposits, which are sometimes hard to see. Deposits can be silver or black from arcing. If there is a suspect area on the ring, take the end of a CLEAN tywrap and gently drag it across the suspect area. You should be able to feel a vibration in the tywrap if a pit or deposit is present. If pits or deposits are found, clean the slip ring tracks.

3 Brush Block Vacuuming and Wear Inspection

1. Disconnect all connections to the brush block. See Figure 1.

   Figure 1. Slipring Brush Block Assembly

   

2. Remove the four-6 mm cap screws that secure the brush block assembly to the gantry.

3. Carefully remove the brush block.

4. Tap brush block lightly with a small hammer to dislodge the dust particles from the brush block.

5. Thoroughly vacuum the signal and power brushes.

6. Inspect each brush tip for wear. Each tip has a triangle stamped on one side (see Figure 2). When the brush wears to the point of the triangle, the brush must be replaced. (For replacement procedures see Slip Ring Brush Block Replacement)

   Figure 2. Inspection of Brush Tip for Wear

   

7. Carefully install the brush block by exerting even pressure perpendicular to the ring surface.

8. Secure the brush block with the four-6 mm cap screws. DO NOT tighten yet.

9. Carefully push the brush block against the position adjustment set screws in the mounting bracket.

10. Remove two brushes from the inside HVDC ring top and bottom. Remember the orientation for later installation

11. Use a flashlight to verify block position is adjusted so the brushes ride in the center of their tracks. Adjust the brush block setscrews, if necessary, to center the brush.

12. Torque the four-6 mm cap screws to 7.9 N-m (70 in-lbs. or 5.8 ft-lbs.).

13. Re-install the two brushes removed to inspect the alignment.

14. Re-install connections to the brush block per the cable labels.

15. Re-install the brush block cover.

16. Re-install the slip ring covers.

17. Vacuum the brush debris that may have been deposited on the gantry base and floor during servicing.

18. Wash your hands thoroughly after servicing any slip ring components.