• Discovery MR750 3.0T System Service Methods
  • 5690009-2EN Revision 4
  • Object ID: 00000018WIA30C8F030GYZ
  • Topic ID: id_12373405 Version: 1.25
  • Date: Oct 11, 2021 3:47:51 PM

Replacing XRMw cable busbars

Prerequisites

Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
230 minutes5 hours2 hours
Tools and test equipment
ItemQuantityPart numberManufacturer
Arc Flash PPE1--
PPE: non-magnetic safety shoes, safety glasses, and gloves1--
Nonmagnetic Titanium Service Tool Kit, Large Set15112581-
Torque Wrench, 8-50 N m Adjustable, non-magnetic15534134 or 5534134-2 -
Nonmagnetic 80 N m Fixed Torque Wrench Kit15790177-
Consumables
ItemQuantityPart numberManufacturer
Loctite #243 (check expiration date)15415261-2-
Alcohol WipesAs needed--
Black Sharpie Pen1--
Replacement parts
ItemQuantityPart numberManufacturer
XZ XRMw Busbar1See FRU Manual-
Y XRMw Busbar1See FRU Manual-
Required conditions
At least one individual doing this procedure must have taken training course GEHC-TECH-AMOL-CT530-01_CURR.
Safety

Before working in any GE Healthcare MR suite or performing any GE Healthcare service procedure, you must:

  • Have read and understood all hazard conditions and safety requirements in the latest revision of the GE Healthcare MR Service Safety Manual (5452735).
  • Have successfully completed all relevant GE Healthcare Environmental Health and Safety (EHS) courses (or for non-GE employees, equivalent workplace training courses).
  • Comply with all site-specific training and workplace safety requirements.

If you have any safety concerns at any time, do not begin work or immediately stop work and move to a safe location. Immediately contact your supervisor or site safety officer for instructions on how to proceed.

About this task

Overview

This procedure describes the replacement or installation process for the eXtreme Resonance Module Revision W (XRMw) busbars.

The system has two busbars: the XZ busbar assembly and the Y busbar assembly. Typically, only one busbar is replaced at one time.

Figure 1. Y and XZ busbars
There are multiple system configurations:
Topic ID: id_SL2924221-1094802

Getting started

Procedure

  1. Order the correct busbars. See Table 1 for the correct configurations.
  2. Order the nonmagnetic torque wrench before starting this procedure.
  3. Do LOTO on the PGR PDU/gradient subsystem. Refer to the MR Service Safety Manual (5452735).
  4. Remove the patient bridge. See Bridge and Longitudinal Drive Belt Replacement.
  5. Remove the magnet enclosure rear end bell. See Rear End Bell Removal and Installation.
  6. Move the rear pedestal away from the magnet to allow access to the busbars.
    Note: Slack in the cables going to the rear pedestal should allow it to be moved back without disconnecting cables. However, it is possible that some cables may need to be disconnected.
Topic ID: id_SL2935244-1094802

Removing busbars

About this task

Typically only one busbar is replaced at a time. The removal and installation processes for Y and XZ busbars are the same. If a different instruction is necessary, the instruction is labeled specifically for Y or XZ.

Procedure

  1. Note: DO NOT remove the clamps on the busbar leads.
    Note:

    Never use the nonmagnetic torque wrench to loosen connections, the torque wrench has a range of 10 - 50 N*m ( 8 – 35lbf*ft), removing Nord-Lock© or Spiralock© threads may exceed the limit of this wrench and destroy the ratchet components.

    If you are removing an M10 busbar (no M12 indicator on the busbar face), remove the M10 nuts and Nord-Lock washers that secure the busbar lugs to the coil. If you are removing an M12 busbar (M12 indicator on the busbar face), remove the M12 SmartBolts and Nord-Lock washers that secure the busbar lugs to the coil. Slide the busbar terminal lugs off of the studs at the coil.
    Figure 2. M12 indicator

    Discard the Nord-Lock washers and stainless steel flange nuts or SmartBolts.

  2. At the top of the busbar, remove screws and the plastic cover from the busbar.
    • (For Y busbar) Remove two screws.
    • (For XZ busbar) Remove three screws.
  3. At the top of the busbar, remove the four M10 brass nuts and Nord-Lock washers that secure the gradient power cables to the busbar terminals. Slide the gradient power cable lugs off of the studs on the busbar.
    • (For Y busbar) Remove four nuts and Nord-Lock washers. See Figure 3.
    • (For XZ busbar) Remove eight nuts and Nord-Lock washers. See Figure 4.

    Discard the Nord-Lock washers.

    Figure 3. (For Y busbar) Disconnecting gradient power cables
    Figure 4. (For XZ busbar) Disconnecting gradient power cables - magnet end
  4. Remove the nuts and washers that secure the busbar to the gradient coil.
    • (For Y busbar) Remove 10 nuts. See Figure 5.
    • (For XZ busbar) Remove six nuts. See Figure 6.

    Discard the brass nuts.

    Figure 5. Y busbar mounting points
    Figure 6. XZ busbar mounting points
  5. Note:

    • DO NOT lift the busbar assembly by holding the leads.

    • (For Y busbar) Make sure the G-10 (glass-reinforced) spacers and rubber washers remain on each mounting stud.
    The busbar assembly can now be removed from the magnet.
Topic ID: id_SL2936573-1094802

Installing busbars

About this task

Typically only one busbar is replaced at a time. The removal and installation procedure for Y and XZ busbars are the same. If a different instruction is necessary, the instruction is labeled specifically for Y or XZ.

Procedure

  1. Note: Do the following:
    • Before installing the replacement busbar, examine the surfaces that will connect the gradient coil and cables for oxidation. If the gradient copper surface is oxidized, clean the surface with a light abrasive pad.
    • DO NOT remove the clamps on the busbar leads.
    • DO NOT lift the busbar assembly by holding the leads.
    • Clean the magnet mounting stud threads with a nonmagnetic brush to remove any remnants of thread-lock material.

      Hand thread a clean M10 nut onto the stud and make sure that the nut rotates freely. The thread should be free of high friction or locking spots.

    • Wipe the studs and the gradient coil terminals clean with alcohol to make sure any particles and dust are removed.
    Slide the busbar assembly (with leads hanging down) onto the mounting studs.
    • (For Y busbar) The Y busbar has 10 mounting studs.
    • (For XZ busbar) The XZ busbar has six mounting studs.
  2. Install a G-10 (glass-reinforced) washer on each stud. Apply one drop of Loctite 243 to the threads of each mounting stud. Then install a brass nut onto each mounting stud.
  3. Starting at the top and moving clockwise between mounting studs, hand-tighten each nut evenly. Again moving clockwise between studs, tighten one full turn (1/2 turn at a time). Stop when 2-3 threads are showing above each nut.
    Figure 7. (For Y busbar) Location of brass nuts
    Figure 8. (For XZ busbar) Location of brass nuts
  4. Note: Make sure of the following:
    • Always use the new Nord-Lock washers that come with the FRU package. DO NOT reuse the old Nord-Lock washers.
    • Nord-Lock washers consist of two pieces, which are generally glued together. Always use a complete set with two pieces joined together in the correct orientation. DO NOT use a separated single piece. If the Nord-Lock washers are separated, or the nuts are untightened, discard the washers and replace them with new Nord-Lock washers only. If new Nord-Lock washers are not available, contact the online center for further instructions.
      Figure 9. Nord-Lock washers
      1Wrong (do not use separated washers)
      2Correct
    • Always shake the Loctite bottle before use.
    Place a new Nord-Lock washer over the stud. Put two drops of Loctite 243 on the exposed thread.
    Note: If there is no stud (M12 connection), do not apply Loctite to the Smartbolts.

    Do not get Loctite on the Nord-Lock washer. Hand-tighten the nut.

    Discard the old washers.

  5. Set the torque wrench appropriately:
    • (For M10 nut/stud configuration) Set the torque wrench to 25 ft-lbs or 33.9 Nm. Install a 15 mm socket on the extension.
    • (For M12 SmartBolt configuration) Set the torque wrench to 59 ft-lbs or 80 Nm. Install a 17mm socket on the extension.
    Note: Make sure that the arrow on the torque wrench is visible. If the arrow is not visible, the torque wrench will not “click” when the proper torque is reached.
    Figure 10. Arrow on nonmagnetic torque wrench
  6. Torque the nut or SmartBolt in the direction of the arrow until the torque wrench reaches the break point.
  7. (For M10 nut/stud configuration) Using a Sharpie pen, place a line from the base of the stud to the nut.
    Figure 11. SmartBolt

    A red indicator means the SmartBolt is not torqued, as shown above; a black indicator means the SmartBolt is torqued.

    Figure 12. Stud and nut or SmartBolt marked to show torque position
    1Black line on nut and stud to show torque position.

    Repeat this process for all terminal connections.

  8. (For M10 nut/stud configuration) Do a second torque operation at each nut to confirm the proper torque of the nut.

    If the nut moved more than one flat from the original position, you must retorque the nut a third time.

    If retorqueing was necessary, re-mark the line on the nut and stud.

  9. Install the safety cover.
    1. Inspect the flame-retardant material (white cloth) for tears or internal damage. Replace the safety cover if the liner is damaged. See the FRU list for the part number.
    2. Make sure the flame-retardant material (white cloth) is folded out around the edges of the safety cover. There should be no openings between the safety cover and the gradient coil.
  10. At the top of the busbar (after applying system cables), install new Nord-Lock washers, and then brass nuts, onto the studs of each busbar.

    Use the torque wrench to tighten the nuts on the top of the busbar to 25 ft-lbs or 33.9 Nm. See Step 5.

  11. At the top of the busbar, install the plastic cover with two screws to the busbar.
    • (For Y busbar) Two screws hold the plastic cover on the Y busbar.
    • (For XZ busbar) Three screws hold the plastic cover to the XZ busbar.

    Always make sure that the stud extends beyond the end of the nut.

    Figure 13. Installation sequence of terminal
    1

    Sequence for installing fasteners:

    1. Power cable lug
    2. Nord-Lock washer
    3. Nut