• Topic ID: id_17423205
  • Version: 5.0
  • Date: Aug 10, 2021 9:57:30 PM

HEMIT Tank Replacement

Prerequisites

Overview

This module describes how to:

  • Disconnect Wires

  • Remove old HEMIT Tank

  • Replace new Tank

1 HEMIT Tank Removal

Procedure

    • danger
    • Electrocution hazard
    • High Voltages present.
    • Use proper lockout/tagout procedures before replacing components. See safety menu of Service Document gui for appropriate procedures.
  1. Move table to its lowest elevation.
  2. Remove power to the gantry using proper Lockout/Tagout procedures.
  3. Remove the side, top, and front gantry covers.
  4. 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.
  5. Turn OFF all the three switches (Axial Drive, HVDC, 120VAC) on the Service Switch Panel.
  6. Remove power at main disconnect (A1) panel. Use proper Lockout/Tagout procedures.
  7. Remove the two M12 screws from the right front gantry cover mounting bracket, remove and set aside the bracket.

    Figure 1. Support Bracket Removal

  8. Rotate the Gantry until the HEMIT Tank reaches the 9 o’clock position.
  9. Cut any tie-wraps.
  10. Use the spanner wrench to remove the high voltage cable connector from the tank on the power unit.

    • Ground the ends of the H.V. cable to the Gantry frame, to endure no voltage exists at the end of the cable.

    • Use rags or paper towels to wipe excess oil from the H.V. Cable Connector and tank well.

    • Stuff the tank wells with paper towels to absorb any oil.

    Figure 2. HV Cable Configuration

  11. Cut any tie-wraps.
  12. Disconnect the 3 cable connector from the HEMIT Tank.

    Figure 3. HEMIT Tank Cable Configuration

  13. Rotate the Gantry until the HEMIT Tank reaches approximately 2 o’clock position.
  14. Engage gantry rotational lock.
  15. Remove the HEMIT Tank from the gantry:
      Notice Image
      • warning
      • severe injury possible.
      • if the hoist hook's lock nut is loose, then the Hemit tank might drop from the hoist, with the resulting in serious injury to service personnel.
      • before using the hoist, check to make certain that the hook's lock nut is not loose. If it is loose, do not use the hoist. instead, order a new hoist.
    1. Attach the hoist to the boom arm in the gantry.
    2. Attach the hoist lifting chain to the lifting bracket on the HEMIT Tank bottom.
    3. Remove slack from the hoist chain.
    4. Remove the 6 bolts that fasten the HEMIT Tank to the rotating base.

      In case of Cj M40, remove 2 bolts that fasten the safety bracket.

      Figure 4. Safety Bracket

    5. Use the hoist to lower the HEMIT Tank to the floor.

      Figure 5. HEMIT Tank Removal

2 HEMIT Tank Installation

Procedure

  1. Ensure that Lockout/Tagout procedure has been applied, and that gantry power is removed.
  2. Ensure that gantry rotational lock is engaged and gantry does not rotate by attempting to rotate gantry by hand.
  3. Using the hoist, attach the new HEMIT Tank to gantry.
  4. Torque the 6 bolts to the following pre-load value.
  5. Torque the 2 bolts for safety bracket to the following pre-load value.
  6. Torque the 8 bolts to the following final value.
  7. Re-connect all the cables.
    note: Follow the following procedure for tightening HV cable ring nuts.
    1. Lightly wet the new rubber quad ring with transformer oil.
    2. Return the quad ring to its slot at the top of the receptacle retaining ring.
    3. Pour transformer oil into the receptacle approximately 13 ml (reference only, please adjust the oil amount as necessary).
      note: DO NOT use the syringe in vertical position, this will result in air bubbles which increase the chances of the high voltage breakdown.

      Figure 6. Filling Receptacle

    4. Align the cable terminal orienting key with the notch in the receptacle.
    5. Slowly insert the cable, to engage the connector pins, and seat the cable in the receptacle.
      note:

      After installing the cable to the receptacle, confirm the transformer oil is spilled over a little from the receptacle as shown in Figure 7.

      If the transformer oil is inappropriate amount, adjust the oil amount as necessary.

      Figure 7. Appropriate Amount of Transformer Oil

      1 HV Cable
      2 Transformer Oil
      3 Receptacle
    6. Tighten the cable ring nut by ¼ to ½ of a full turn by spanner wrench after the gap is closed and friction is felt by hand.
    7. Carefully wipe up all excess oil.