Interlocks

The Interlocks are dependent on the design. They are to be defined during design by the contractor, according to the safety requirements, manual operation and maintenance needs.

ESO has defined three types of interlocks:

Motion Stop Interlocks: general interlocks generated by actuation of the Motion Stop switches mounted in the AT. One of the push-buttons must be of type locking key. All Motion Stop have the same action; their location and quantity are defined in AMOS Control System document [RD03], Chapter 12.

Local Interlocks: these interlocks are used to prevent specific actions between equipment.

Equipment Interlocks: these interlocks are used to prevent specific actions within an equipment.

The hazard analysis is provided in [AD06].

Interlocks Table:

Subsystem >Action Cause Recovery Action

Generating Receiving

VLTI Motion Stop
in Control Room All subsystems except those supplied by battery and small axes
Main Drives immobilized
Except small axes (NFD, CFD, FSS, M2, M10). Button pressed
or key removed Release button
or Replace key

AT Motion Stop
on AT

Transporter PLC

Power Shutdown
Watchdog
Reset Transporter PLC

Hardware Limit Azimuth Drive immobilized Limit Switch Move back into stroke

Hardware Limit Altitude Drive immobilized Limit Switch Move back into stroke

Interior Door Azimuth & Transporter up-down Drives immobilized Limit Switch Close the door

Alt-Locking pins Altitude Drive immobilized Limit Switch Put Alt-Locking pins into unlocking position

Altitude Parking
Telescope Up
Shell closing(if Telescope is not in lowest position)
Drive immobilized

Parking Switch
Put Altitude axis in Parking position

Stroke limit Azimuth & Azimuth Cable Wrap Drive immobilized Azimuth CWP Limit Switches Move back Az axis into stroke

Enclosure Area Azimuth & Enclosure closing
(+ PLC inhibit on enclosure opening & Tel. up-down)
Drives immobilized Key in EWA position
Turn key in "NOT EWA" position

Transporter PLC Enclosure Close Winshield Anemometer give too high windspeed none

Relocation status Altitude & Azimuth Alt Az Drives immobilized Relocation not finished finish Relocation

Important Note: Before undertaking any recovery action, one has to have well understood why the corresponding interlock has been activated and take the corrective action to prevent from activating the interlock in the future.

Moreover, there are many internal locks. The Transporter PLC checks the feasibility of each operator command, the Sauter PLC is equipped with a watchdog that stops the air conditioning system and switches the alarm status on, each electrical motor is equipped with PTC sensors, each inverter is equipped with overcurrent protection. See [RD 03] and [AD 06].

Last modified: Wed Jan 150 10:20:44 MET 2003