1. Camera Maintenance and Access
Martin Nordby, Kevin Reil
August, 2017 R2

2. Introduction Goals of the session
Review camera maintenance access use cases
Agree on access regions and use cases for camera operations and maintenance
Develop first-cut list of access and recovery processes based on designs of TMA, GIS, and dome access control—with a goal of using these to set durations for maintenance tasks
The camera is somewhat unique in that maintaining almost any part of the camera likely affects other parts of the system and may prevent other operations from taking place
Defining these incompatibilities is important for understanding commissioning and operations time available for various maintenance activities
However, this will be much easier once we have a better idea of the steps needed to perform the various maintenance activities
For this exercise, I’ve defined a “use case” as:
A grouping of activities that all require the same access, contamination control, and general personnel support
Sets of activities that can all be accomplished by way of the same access, contamination control, and general personnel support
Camera Systems Integration

3. Camera assembly and access regions
Back flange bay covers
Access to:
-Carousel power and control electronics
-Filter loader connect point
-Auto changer and shutter interconnects
-Purge ducting
Camera has been designed with servicing plans in mind
Portholes for access into camera volume
Access to:
-Carousel clamps
-Cryostat housing
-Carousel rotating assy
Utility Trunk
Filter loader mount and access hatch
Access to:
-Auto changer rails
Shroud panels allow for access into camera front flange
Access to:
-Auto changer
-Shutter
-L2-S2 and L3-S1
-Purge ducting
UT sliding doors in accessible region through hexapod
Access to:
-Cam electronics
-Cam Vol Purge cabinet
Back flange
L1-L2 Assembly
Camera housing
Shroud
Camera Systems Integration

4. Partially assembled camera with panels removed
Open region to allow for removal of auto changer unit while on the telescope
Parts of carousel visible through open porthole
Shroud panels removed, showing longerons and L1-L2 interface rings
Camera Systems Integration

5. On-camera maintenance use cases
These are described in LCA-282, Camera Operations Concept Document
Access/Secure Camera Body
Stage equipment on platforms on for maintenance work
Mount clean tent, remove shroud panels
Prepare for accessing front flange mechanisms and optics inside camera
Maintain Mechanisms
Troubleshoot and service shutter: check belt tension, H-E switches, E-box and controls, etc.
Troubleshoot and service auto changer: check clamps, motors, lubricate ball screws, etc
Remove porthole covers to service carousel clamps
Remove/Replace Mechanisms
Replace auto changer unit
Replace shutter
Inspect Components in Camera Body
Inspect and align L1-L2 struts
Inspect and clean L2-S2 and L3-S1
Access Front of Camera
Inspect, clean L1-S1
Mount/de-mount L1 lens cover
Mount/de-mount SMRs
Camera Systems Integration

6. On-camera maintenance use cases (cont.)
Swap Out Filter
Install empty filter loader to remove filter
Install loaded filter loader to install new filter
Access Back Flange
Remove bay covers
Access carousel components, cabling, purge lines
Lubricate carousel ring gear, replace motor, brakes, unclamp motors, electronics components
Check torque on camera—rotator mounting screws
Access/Secure Utility Trunk
Prepare to open UT: install auxiliary blower unit, clean UT outside
Open UT doors
Replace Component in Utility Trunk
Replace auxiliary electronics components
Replace Camera Volume Purge cabinet filters
Service, Leak Check Vacuum Systems
Crane in pump cart and equipment
Pump cryostat, Heat-X vacuums
Leak check cryostat seals
Camera Systems Integration

7. Refrigeration use cases
Access and service compressor cabinets
Evacuate, purge, charge refrigeration circuit
Check and service compressor units: oil levels, refrigerant charge, etc.
Service refrigeration lines from top end isolation valves at CCW
Evacuate refrigeration circuit
Purge circuit during disconnect
Service refrigeration lines at bulkhead plate
Mate/de-mate refrigeration connections
Leak check refrigeration connections
Camera Systems Integration

8. Questions and issues to address and consider
What capabilities do we have for staging equipment on the floor and sub-floor for later maintenance?
What are expected times for crane lifts from TMA floor and lower enclosure to camera?
How can we access relief valves outside of CCW on the top end?
How do we access the bulkhead plate; is this considered a confined space?
Some of these use cases require exclusive control of certain resources—crane, azimuth and azimuth drives, rotator/hexapod drives, L1/M1 region
As we further define use cases, this needs to be captured, since it will affect our ability to do maintenance in the dome
Camera Systems Integration

9. Regions needing access for camera maintenance
Dome floor
Sub-floor for refrig compressor cabinet servicing
Camera maintenance platforms (for UT maintenance and filter loading)
Camera platforms and scaffolding (for in-camera maintenance)
Isolation valves near CCW on TEA
Bulkhead plate inside TEA
Questions
What needs to happen to provide safe access to these regions, starting from when the operator takes the last image of the night?
What are expected procedures and rough timing for dome search and close-up after an access?
What are expected procedures and rough timing for sub-floor search and close-up after an access?
What needs to happen to recover from in-camera maintenance?
Camera Systems Integration

10. Installing and removing the camera and integrating structure
The camera is largely a self-contained system that will be tested and verified prior to mounting to the telescope
However, some key systems need further assembly and testing during and after the process of integrating to the telescope
Refrigeration system interconnection and commissioning
Dynalene system interconnection and commissioning
DAQ connectivity and throughput testing
For the refrigeration system, in particular, this is expected to take some time—estimates based on the most recent prototyping and process control demonstrations:
15 additional shifts needed for refrigeration system activities during Camera/IS assembly and installation on the telescope
3 additional shifts needed for refrigeration system activities when removing the Camera/IS, if the system does not need to be operated on the ground
Likely applicable for M2 mirror re-coating
8 additional shifts needed for refrigeration system activities when removing the Camera/IS, if the system will be operated on the ground
These dates need further scrubbing, and include the following caveats:
This assumes that the refrig pathfinder has already proved out performance of the compressor chasses and allowed for cleaning and drying of the lines running up the TMA
Much of this work requires exclusive access to the TMA and sub-floor regions, with the TMA locked out
Camera Systems Integration

11. Refrigeration integration and testing during Camera/IS install
Mount camera to Integrating Structure (on the ground)
Interconnect camera and CCW refrig lines at bulkhead plate – 3 days
Assumes camera refrig system parts have already been pressure/leak checked and cleaned
Purge during installation from isolation valves
Leak check connections from isolation valves
Mount Integrating Structure/Camera assembly on TMA
Interconnect TMA and CCW refrig lines at isolation valves – 3 days
Purge through isolation valve port from compressor cabinets
Leak check
Complete system leak check – 2 days
Dry out entire refrig circuit including evaporators – 4 days
8 systems simultaneously, as long as we have enough dry nitrogen flow
Process will take longer if boil-off nitrogen isn’t available
May take less time than initial dry down if everything has been kept clean
Evacuate 2 cold and 6 cryo circuits – 2 days (8 systems simultaneously)
Charge 2 cold and 6 cryo systems – 1 day (one person handling one system at a time)
System is ready for cooldown
Camera Systems Integration

12. Refrigeration preparations during Camera/IS removal
Option 1: Camera is removed and set aside, with no plans to run the system
Total duration of refrig work: 3 shifts
Close CCW isolation valves and recover refrigerant from valve tee – 2 days (one system at a time)
Disconnect lines at CCW isolation valve while under purge, capping disconnected lines – 1 day
Option 2: Camera is removed to be run in the white room
Total duration of refrig work: 8 shifts
Recover/collect charge while camera is in the process of warming up – 1 day (all systems simultaneously)
Backfill with nitrogen from compressor cabinets – 1 day
Disconnect lines at CCW isolation valve while under nitrogen purge, capping disconnected lines – 1 day
De-mount IS/Camera Assembly from telescope
Disconnect lines at bulkhead plate while purging from isolation valves – 1 day
Remove Camera from Integrating Structure and mount to Stand
Connect to maintenance system umbilical lines – 1 day
Assumes that maintenance system lines are in a clean, dry, leak-tight state. Maintenance system lines up to the isolation valves can be pre-evacuated.
Leak check from compressor cabinets in maintenance area – 1 day
Evacuate evaporator side of plumbing up to isolation valves – 1 day
Charge 2 cold and 6 cryo systems – 1 day (one person handling one system at a time)
System is ready for cooldown
Camera Systems Integration