Override Door Lock Procedure

Sometimes a GIS door lock does not operate as expected. This can be because of one of several causes. Because the locks that prevent access to hazardous zones are an important functional safety aspect of the Global Interlock System it is equally important to understand why they are not functioning as expected and that alternative means to preserve safety are used if they must be overridden.

Before attempting to override or bypass a door lock, you must attempt to resolve any issue with hardware.

Possible causes:

• Safety function faulted

  • Trapped key switch instruction faulted

  • Door locking solenoid instruction faulted.

• loss of communications

• GIC not running

• subsystem LIC not running

• hardware failure

Operator Steps to resolve

1. Ensure that proper trapped key sequence has been followed.

2. Remove Trapped Key. Re-insert and turn. Listen for click from solenoid.

3. Try opening the door again.

4. Press GIS reset. Repeat 1 through 3.

Technician Steps to resolve

1. Verify that hazards within the hazardous zone are stopped.

2. Verify that no associated safety instructions are faulted.

3. Perform door reset via the TIM HMI.

   1. login

   2. goto Engineering….Doors

   3. press corresponding door reset button.

   4. Try opening door again.

Engineer steps to resolve

1. Verify the GIC is running.

2. Verify that subsystem LICs are running.

3. Verify that IO is responding.

4. Examine PLC logic to determine exact cause.

5. Resolve any issues.

I found the problem but I can’t fix it right now.

There might be times when the problem is found and understood but cannot be remedied immediately, such as power off to part of the GIS. Then it is permissible to override the door lock.

1. Make a log entry in the Safety Bypass Log.

   1. Explain what the problem is and why it can’t be resolved.

2. Ensure there is an alternative means to maintain safety. i.e. lockout of hazardous motion.

3. From the Engineering…Door display press the appropriate Door Override button.

   1. You will have a limited time to open the corresponding door before it returns to normal operation.

I need to override the door

There may be times when the system is operating as designed but it is desired to override the doors. One such example is having personnel on the upper Enclosure walkways during operation (see Access to Enclosure Catwalks during observing). If there is a standing procedure use it otherwise follow the instructions below.

1. Perform a Job Hazard Analysis.

2. Ensure there is an alternative means to maintain safety. i.e. lockout of hazardous motion.

3. From the Engineering…Door display press the appropriate Door Override button.

   1. You will have a limited time to open the corresponding door before it returns to normal operation.