Engineering -- Doors Display
- Tim Williams
The Engineering – Doors display allows resetting or sensors and unlock overrides to the hazardous access control doors. This display is password protected.
WARNING
Overriding a door lock is inherently hazardous as it bypasses key safety design elements. It should only be used in extraordinary circumstances, such as emergencies or system failures.
Alternative measures shall be employed to ensure safety.
Death or serious injury may result.
Door Reset
The various ‘door reset' allow the operator to cycle power to the guard locking switches and sensors.
Removing power to the sensor will not unlock the associated door.
Occasionally, the guard locking sensor will fault. When the guard locking sensor detects a fault it stop responding and enter a fault state. Clearing the fault state requires power cycling the switch. This can be readily accomplished by pressing the corresponding ‘door reset’ button.
What causes guard lock faults
The guard locking switches and other sensors have built-in OSSD outputs. These are designed to detect failures of the device or associated wiring.
If a mechanical load (pressure) is applied to the gate during unlocking, the TLSZR guard locking switch goes to a fault mode.
The TLSZR Power to Release switches are more tolerant but may not withstand rapid locking and unlocking.
Door Override
Overriding a door lock is inherently hazardous as it bypasses key safety design elements. It should only be used in extraordinary circumstances, such as emergencies or system failures.
Death or serious injury may result.
The various doors that make up the entrances to the Hazardous Access Zones are designed to lock unless certain trapped keys are in place. This is one of the key safety elements of the the Hazardous Access Zones.
Because the doors require positive confirmation that the proper trapped keys are in place, it is possible that a system failure will render a door inoperable. The most common being the GIC or one of the LIC taken off-line or loss of network connectivity.
Another circumstance would be in case of emergency, such as a fire, where immediate access is required.
Pressing an ‘unlock override’ button will unlock the door immediately.
For example, unlocking door 210A (Coudé Mezzanine) will cause the Coudé Rotator to stop as having that door locked is required for the Coudé Rotator permissive signal.
Because this bypasses the trapped key system the danger comes from restarting the system without knowing if personnel have entered a Hazardous Access Zone.