• SIGNA™ Hero 3.0T Service Methods
  • 5852800-8EN Revision 1.0
  • Object ID: 00000018WIA30BEC230GYZ
  • Topic ID: id_15667341 Version: 1.23
  • Date: Jan 26, 2022 3:37:20 PM

VRMw cable busbar replacement

Prerequisites

Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
23 hours5 hours3 to 4 hours
Tools and test equipment
ItemQuantityPart numberManufacturer
Pair: Nonferrous Safety Shoes1 for each person--
Safety Glasses1 for each person--
Pair: Cut-Resistant Gloves1 for each person--
Arc Flash PPE1--
Nonmagnetic Titanium Service Tool Kit, Large Set15112581-
Torque Wrench, 8-50 N m Adjustable, non-magnetic1

5534134 or 5534134-2

-
Consumables
ItemQuantityPart numberManufacturer
Loctite #243 (check expiration date)15415261-3-
Loctite 271 (check expiration date)146-170684P2-
Alcohol WipesAs needed--
Black Sharpie Pen1--
Replacement parts
ItemQuantityPart numberManufacturer
XZ VRMw Busbar 1

Refer to FRU Manual

-
Y VRMw Busbar 1

Refer to FRU Manual

-
Required conditions

Remove the rear endbell.

Removing the rear endbell

Table 1. Safety

About this task

This procedure describes the replacement or installation process of the VRMw Cable Busbar.

There are two separate busbars; XZ busbar assembly and the Y busbar assembly. Typically, only one busbar will be replaced at one time.

Figure 1. Y and XZ busbars
Topic ID: id_SL2924221-1180649

Lockout/Tagout

About this task

Follow all safety lockout/tagout procedures:

Procedure

LOTO for the ISC
Topic ID: id_SL2935244-1180649

Y busbar removal

Procedure

  1. Remove the cable clamp.
    Note: DO NOT remove the clamps on the busbar leads.
    Figure 2. Cable clamps
  2. At the service end, remove the safety covers from the end of the Y busbar cable connections.
    Figure 3. Safety cover
  3. Remove two M10 brass nuts and Nord-lock washers that secure the busbar lugs to the coil. Slide the busbar terminal lugs off of the studs at the coil.
    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.

    Figure 4. Removing brass nuts and Nord-Lock washers - coil end
  4. At the top of the busbar, remove two screws and the plastic cover from the busbar.
  5. At the top of the busbar, remove the four M10 brass nuts and Nord-lock washers that secure the busbar lugs to the magnet. Slide the busbar terminal lugs off of the studs on the busbar.
    Figure 5. Disconnecting gradient power cables
  6. Remove the ten brass nuts and G10 washers that secure the Y busbar to the magnet.
    Figure 6. Y busbar mounting points
  7. Note: Observe the following:
    • DO NOT lift the busbar assembly by holding the leads.
    • Make sure the phenolic spacers and rubber washers remain on each mounting stud.
    The busbar assembly can now be removed from the magnet.
Topic ID: id_SL2936573-1180649

Y busbar installation

Procedure

  1. Make sure a the rubber bushings (smaller side faces out) are on each mounting stud. Make sure the coil-side mating surface is clean and void of epoxy.
    Figure 7. Rubber bushing
  2. Note: Observe the following:
    • Before installing the replacement busbar, inspect the surface that will connect the gradient coil and cables for oxidation. If the surface is oxidized, clean the surface.
    • DO NOT remove the clamps on the busbar leads.
    • DO NOT lift the busbar assembly by holding the leads.
    Slide the Y busbar assembly (with leads hanging down) onto the ten mounting studs.
  3. Apply Loctite 271 (approximately 1 or 2 drops) to the threads of each mounting stud and install a G10 washer and brass nut onto each mounting stud.
  4. 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). Conclude when 2-3 threads are showing above each nut.
    Figure 8. Location of brass nuts - Y busbar
  5. Install the busbar terminal lug to the VRMw gradient coil terminal.
  6. Note: Observe 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 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
    Put a new Nord-Lock washer over the stud. Put two drops of Loctite 243 on the exposed thread.

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

    Discard the old washers.

    Figure 10. Loctite on stud
    1Busbar terminal lug
    2Loctite on stud
    3Nord-Lock washer (installed after lug)
    Figure 11. Tightening brass nuts
  7. Set the torque wrench to 25 ft-lbs or 33.9 Nm. Install 15 mm 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 12. Arrow on nonmagnetic torque wrench
  8. Torque the nut in the direction of the arrow until the torque wrench reaches the break point.
  9. Using a Sharpie pen, place a line from the base of the stud to the nut.
    Figure 13. Stud and nut marked to show torque position
    1Black line on nut and stud to show torque position.
  10. Restore and secure the safety cover.
    Figure 14. Safety cover
  11. Install the cable clamp.
    Figure 15. Cable clamp
  12. At the top of the busbar (after applying system cables), install Nord-lock washers (new), then brass nuts, onto the studs of the busbar. Hand-tighten brass nuts plus a half turn with a 17 mm non-magnetic wrench. Do not overtighten nuts. At the top of the busbar, install plastic cover with two screws to the busbar.
    Figure 16. Installation sequence of terminal
    Note: Observe the following:

    • Proper torque to the nuts holding the busbar lugs is critical to the long-term stability of the gradient subsystem.

Topic ID: id_SL2935245-1180649

XZ busbar removal

Procedure

  1. Remove the cable clamps .
    Figure 17. Cable clamps
  2. Remove eight M4 x 10 mm screws and two Safety Cover Tops (clear plastic) from the busbar.
    Figure 18. XZ busbar safety covers
  3. Remove four M10 brass nuts and Nord-lock washers that secure the busbar lugs to the gradient coil.
    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.

    Figure 19. Removing brass nuts and Nord-Lock washers - coil end
  4. At the top of the busbar, remove three screws and plastic cover from the busbar.
  5. At the top of the busbar, remove eight M10 brass nuts and Nord-lock washers that secure the busbar lugs to the system. Slide the busbar terminal lugs from the studs on the busbar.
    Figure 20. Disconnecting gradient power cables - magnet end
  6. Remove the six brass nuts and washers that secure the XZ busbar to the magnet.
    Figure 21. XZ busbar mounting points
  7. Note: DO NOT lift the busbar assembly by holding the leads.
    The busbar can now be removed from the magnet.
Topic ID: id_SL2936759-1180649

XZ busbar installation

Procedure

  1. Make sure a the rubber bushings (smaller side faces out) are on each mounting stud. Make sure the coil-side mating surface is clean and void of epoxy.
    Figure 22. Rubber bushing
  2. Note: Observe the following:
    • Before installing the replacement busbar, inspect the surface that will connect the gradient coil and cables for oxidation. If the surface is oxidized, clean the surface.
    • DO NOT remove the clamps on the busbar leads.
    • DO NOT lift the busbar assembly by holding the leads.
    Slide the XZ busbar assembly (with leads hanging down) onto the six mounting studs.
  3. Apply Loctite 271 (approximately 1 or 2 drops) to the threads of each mounting stud and install a G10 washer and brass nut onto each mounting stud.
  4. 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). Conclude when 2-3 threads are showing above each nut.
    Figure 23. Location of brass nuts - XZ busbar
  5. Install the busbar terminal lug to the VRMw gradient coil terminal.
  6. Note: Observe 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 correct orientation. DO NOT use a separated single piece.
    Figure 24. Nord-Lock washers
    Place a new Nord-Lock washer over the stud. Put two drops of Loctite 243 on the exposed thread.

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

    Discard the old washers.

    Figure 25. Loctite on stud
    Figure 26. Tightening brass nuts
  7. Set the torque wrench to 25 ft-lbs or 33.9 Nm. Install 15 mm 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 27. Arrow on nonmagnetic torque wrench
  8. Torque the nut in the direction of the arrow until the torque wrench reaches the break point.
  9. Using a Sharpie pen, place a line from the base of the stud to the nut.
    Figure 28. Stud and nut marked to show torque position
    1Black line on nut and stud to show torque position
  10. Restore and secure the safety cover.
    Figure 29. Safety cover
  11. Install the cable clamps.
    Figure 30. Cable clamps
  12. At the top of the busbar, place the terminal lugs of the gradient power cables onto the studs of the busbar.
    Figure 31. Busbar to gradient power cable connection - top
  13. Install Nord-lock washers, then brass nuts, onto the studs of the busbar. Hand-tighten brass nuts plus a half-turn with a 17 mm non-magnetic wrench. Do not overtighten nuts.
    Note: Observe the following:
    • Proper torque to the nuts holding the busbar lugs is critical to the long-term stability of the gradient subsystem.
  14. At the top of the busbar, install plastic cover and three screws to the busbar.