Temporary Aperture Cover Bypass Procedure

Owned by Tim Williams
Last updated: Aug 07, 2023
2 min read

Background

If the Aperture Cover drives fault, the GIS will close the light path, preventing M1 from opening and will try to force the Aperture Cover to close. Occasionally, the Aperture Cover drives will fault at the end of their opening motion with a standstill fault.

Because the light path logic has been tripped, the GIS checks for the both the M1 cover and aperture cover to close. Due to the drive fault, the aperture will fail to close. This causes a GIS Fault. To clear this fault both the aperture cover and M1 cover must be closed first. This results in a catch-22 of opening the aperture cover, drive fault, and then GIS fault, which will prevent progress as long as the drive faults continue.

To get around this we need to open the aperture cover and reset the drives. However, the logic will close the light path if this happens, which will lead to an aperture cover timeout fault. So, we temporarily force the ready bit on. This will give us time to reset the drives. Then we can disable the bypass and continue normally.

Before bypassing

  1. Ensure Aperture Cover is closed.

  2. Reset GIS using front panel button.

  3. Reset GIS faults using engineering screen on HMI.

  4. Verify that Aperture Cover is not forced closed by the GIS.

Bypass Procedure

This procedure only bypasses the signal from the EMCS to the GIS indicating the drives are ready-to-start. As written, it is only intended to bypass long enough to affect a reset of the drives without tripping the GIS’s light path logic. Do not leave the bypass active.

  1. Toggle ApCover_Ready_Bypass in the EMCS PLC on. (Rung 31 of program EMCS_to_LIC in the Main Task)

  2. Open Aperture Cover fully.

  3. Reset Aperture Cover Drives (if faulted).

  4. Verify ApertureCover_Drives_RTS is on.

  5. Toggle ApCover_Ready_Bypass in the EMCS PLC off.

  6. Verify Comm_EMCS_to_LIC.DATA[17].3 remains on.

  7. Open M1 cover normally.

  8. Observe.

  9. Profit.