• Topic ID: id_17423054
  • Version: 6.0
  • Date: Sep 26, 2020 10:14:43 PM

Slipring Brush Block Replacement

Prerequisites

Overview

This procedure defines the necessary steps to replace a brush block assembly.

Procedure

  1. Move table to its lowest elevation.
  2. Remove gantry right side cover.

    Refer to Replacement > Gantry > Enclosure > (Cover Removal Procedures).

  3. Stop the rotor of X-ray tube in case of Liquid Bearing Tube before HVDC off. Refer to Liquid Bearing Tube Rotor stop procedure for details.
    4. Notice Image
    • notice
    • Always turn OFF the HVDC before the 120 VAC. Turning OFF 120 VAC power before HVDC power can result in equipment damage.
  4. Turn OFF all 3 service switches (Axial Drive, HVDC, 120VAC) on the Service Switch Panel.
    • danger
    • Electrocution hazard
    • High Voltage present.
    • Use proper lockout/tagout procedures before replacing components. See safety menu of Service Document gui for appropriate procedures.
  5. Perform Lockout Tagout for system power (A1 disconnect) prior to replacing this component.
  6. Remove the gantry left side cover and top covers, and slide the rear cover backward.
  7. Remove the bore maintenance cover.

    Figure 1. Slip Ring Brush Block

  8. Remove the upper-left and lower-left safety covers of the Slip Ring by unscrewing their captive screws.
  9. Remove brush block safety cover (4 screws with 4 mm hex wrench).
  10. Disconnect all cable connections to Brush block Figure 2.

    Figure 2. Slipring Brush Block Assembly

    11. Notice Image
    • notice
    • Do not touch brushes with your fingers. Transfer of carbon dust can occur which can then be spread to other components touched.
  11. Remove four (4) 6 mm cap screws that secure brush block assembly to gantry.
  12. Carefully remove brush block.
    note:

    New brush tips are supplied with the brush block. Do not reuse old brushes.

  13. Clean the slip ring prior to installing the new brush block and brushes. Use the PM Procedure for cleaning the slip ring.
  14. Install the new brush block and secure with the four (4) 6 mm cap screws. Do not tighten yet.
  15. Push the brush block against the position adjustment set screws in the mounting bracket.
  16. Using a flashlight, look into the top and bottom High Voltage brush locations on the inner HV ring (inside edge of slip ring furthest from brush block mounts). Verify the brush 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 on the slip ring track.

    The examples below show a good and bad brush block alignment. In the good example, the slip ring track is centered in the brush holder. In the example of a bad alignment, the edge of the slip ring track can be seen on the right side only.

    Figure 3. Good Brush Alignment Example

    Figure 4. Bad Brush Alignment example

  17. Torque the four (4) 6 mm cap screws to:
    18. Notice Image
    • notice
    • Brush Contamination Possible. Do not touch brushes with your fingers. The skin oils will contaminate the brush and reduce usable life and potentially create future failures.
  18. Install the new brushes supplied with the new brush block as torque as shown below.

    Figure 5. Brush Block Torque

  19. Reassemble gantry.
    1. Install power lines to brush block per cable labels.
    2. Install brush block cover and slip ring covers.
      note: To avoid damage to the slip ring GND and Harness, plesae bundle them carefully before installing the slip ring upper-left cover.

      Figure 6. Slip Ring Upper-Left Cover (5372512-2) without Additional Notch

      Figure 7. Slip Ring Upper-Left Cover (5372512-2) with Additional Notch

    3. Install gantry cover mount over top of brush block.
    4. Install Gantry covers and restore power to system.

Finalization

  1. Restore power to the system. Verify proper operation by running verification scans. Verification procedure should consist of:
    1. From the Common Service desktop, Diagnostics tab, run the Axial Functional Test, rotating the gantry for 600 seconds to set the new brushes. Exit axial functional when done.
    2. Run 5 stationary and 5 rotational scans with x-ray. The technique is not important. It is important to exit the exam, because this triggers the “DIP Stats” update.
    3. From the Common Service Desktop, Diagnostics tab, select RTS viewer
    4. Choose the DIP selection and view each scans DIP stats. There should be no FEC Failures or Sync Errors. See below for example portion of stats.


      Exam Number:  00263,ENDEXAM
      Date:  Fri Mar 21 02:05:33 2008
      Offset Data Bytes                                            0                         Bytes
      Image Data Bytes                                            0                         Bytes
      Number of Das Data Buffer Overruns              0                         Overruns
      abort                                                               0                         Aborts
      FEC Attempts                                                 0                         Bytes
      Bit Error Rate                                                  0.0                      Rate
      FEC Failures                                                   0                         Failures
      Num of SYNC Errors                                      0                        Errors
      View interpolations                                           0                        Interpolations

    5. Select the TGP and ORP low speed stats and verify zero disconnects, see below for example portion of ORP stats.


      ORP Low Speed Com Stats                
      Exam Number:  00713,ENDEXAM
      Date:  Fri Sep 26 09:52:40 2008
      Short_Brush_Disconnect                                       0                       < 200ns
      Medium_Brush_Disconnects                                 0                       < 100us
      Long_Brush_Disconnects                                      0                       > 100us

  2. Perform a System Scanning Test from the Functional Checks menu of the service manual.