Enclosure Safety Functions

Enclosure Motion Control LIC

The Enclosure Motion Control LIC is responsible for interlocks, limits, and emergency stop functions for the Enclosure Azimuth, Shutters, Cable Wraps, Entrance Aperture; Bridge Crane, Jib Cranes, Rear Access Doors, and TEOA Platform.

This LIC is also the connection point for emergency stop devices located at or near the above items.

Enclosure Azimuth Axis

Enclosure Azimuth Positive Final Travel Limit

When an Enclosure Azimuth Positive Final Limit is detected by using combinational logic of the End Stop position and the final limit switches, the reaction of the GIS is to remove Enclosure Azimuth drive power (category 0 stop) and apply the brakes.

Enclosure Azimuth Negative Final Travel Limit

When an Enclosure Azimuth Negative Final limit is detected by using combinational logic of the End Stop position and the final limit switches, the reaction of the GIS is to remove Enclosure Azimuth drive power (category 0 stop) and apply the brakes.

Enclosure Azimuth Cable Wrap Over Tension

The GIS shall inhibit motion and remove power to the Enclosure Azimuth Drives if the tension of the Azimuth Cable Wrap exceeds predetermined limits.

Enclosure Azimuth Personnel Trapped Key Interlock

This is actually a group of trapped keys which when one or more are removed inhibit Enclosure Azimuth motion by removing power. This key is required to enter the Azimuth Cable Wrap or Azimuth Mechanical areas. In manual mode (Enclosure Pendant installed and enabling grip held) it may be muted to allow Enclosure Azimuth rotation. It is also be required to enable the exterior boom lift.

Altitude Axis

Shutter Personnel Trapped Key Interlock

This is actually a group of trapped keys which when one or more are removed inhibits Enclosure Shutter motion by removing power.

Cranes

Bridge Crane Not Stowed

When in automatic mode, if the Bridge Crane is not stowed (i.e. hook not fully up, trolley at end-of-travel, and bridge fully towards the rear of the enclosure) the GIS removes drive power from the both the Altitude and Azimuth telescope drive controllers (category 0 stop).

If the enclosure has the pendant connected, Enclosure Azimuth motion may be enabled for safe-limited speed.

Bridge Crane Interlock

The GIS shall inhibit (category 0 stop) the Bridge Crane unless the following conditions are true:

• The telescope is parked.

• The telescope azimuth and altitude drives are disabled.

• The telescope brakes are engaged.

Jib Crane Not Stowed

If the GIS detects that the Jib Crane is not stowed (i.e. hook not fully up, jib fully towards the wall of the enclosure) the GIS removes drive power from the both the Altitude and Azimuth telescope drive controllers (category 0 stop).

Jib Crane Interlock

The GIS shall inhibit (category 0 stop) the Jib Crane unless the following conditions are true:

• The telescope azimuth and altitude drives are disabled.

• The telescope brakes are engaged.

Entrance Aperture Cover Interlock

The enclosure entrance aperture cover is allowed to open under specific circumstances.

Open

If the M1 cover is closed or there is no sunlight on the M1 the Entrance Aperture Cover may open. Additionally if the telescope is pointed at the sun and the heat stop shutter is open and heat stop is not in an over-temperature condition the Entrance Aperture Cover may open.

TEOA Access Platform

The TEOA Access Platform may only be deployed when the telescope mount is aligned in azimuth with the platform and the telescope altitude is at least 25° (this measurement needs to be verified). This allows the platform and then the guard rails to be deployed. The TEOA Platform may only be raised once the telescope altitude is above 25° and the guard rails have been stowed.

Operating Sequence

To deploy the TEOA Access Platform:

1. With telescope altitude above 25°, align telescope azimuth with TEOA maintenance position.

2. Lower TEOA platform fully.

3. Deploy TEOA guardrails.

4. Lower telescope altitude to TEOA maintenance position.

To retract the TEOA Access Platform:

1. With the telescope parked at the TEOA maintenance position, raise telescope altitude to above 25°.

2. Retract the TEOA guardrails.

3. Raise the TEOA platform fully.

Additionally, when the TEOA Access Platform is not stowed, Enclosure Azimuth motion and Telescope Azimuth motion is inhibited.

However, the Telescope Altitude axis is required to lower into position when the TEOA Access Platform in not stowed. Telescope Altitude motion shall be permitted only when the TEOA Access Platform is fully deployed or fully retracted.

Facility Thermal System LIC

Vent Gates

None currently identified

Enclosure Cooling

Enclosure Coolant Leak

This safety function monitors supply and return flow rates. If the delta of supply and return rates exceeds a predetermined threshold the GIS commands a controlled stop of the pumps and then disables power (category 1 stop).

Enclosure Dehumidification High High Humidity

In the event of a high wet bulb temperature in the Enclosure exceeds a predetermined level the GIS shall close the M1 cover, close the Aperture Cover, command a controlled stop of the Enclosure Altitude Axis, inflate the shutter seals, and command the Enclosure Dehumidification system to start.

Enclosure Rear Door

None currently identified