NIRC Installation and Removal

The NIRC is installed in the IR Forward Cass Module by lowering it vertically using a special Installation Fixture. The crane should have a precision handling device such as a Hydroset. The the installation fixture is designed to protect the dewar from hitting the module or any other instrument properly positioned in the module. The dewar is attached with two captive socket head bolts to a special mounting plate that reproducibly aligns the dewar in the module. It is assumed that the dewar starts in its handling fixture and that the dewar mounting plate is already attached to the module mounting surface.

NIRC Installation

1. Disconnect all cables and cap open sockets.
2. Remove all pumping fittings and cap the vacuum ports.
3. Check that Tertiary Mirror Module is properly attached with its lid shut.
4. Rotate dewar to the horizontal with window down and electronics boxes up.
5. Prepare crane with precision handling device (Hydroset).
6. Hook Installation Fixture by its adjustable wire sling to precision lifting device on crane.
7. Adjust sling so that the end of the Installation Fixture with the movable ears is about 10 inches above the end with the cross bolt.
8. Check that the attachment pin is out of the center boss and in the 1/2 inch hole in the top of the fixture.
9. Position the fixture above the dewar with the ears around the window end and the cross pin of the fixture just in front of the dewar hook by the electronics boxes. The pin is released by holding the pin shoulder between the index and middle fingers and pushing in the button on the end with the thumb. This retracts the ball on the other end allowing the pin to be extracted.
10. Watching for the socket caps, slide the cross bolt into the hook on the dewar.
11. While keeping the bolt in the hook, lower the fixture with the crane until the boss in the middle bottom of the fixture goes around the mating boss on the dewar.
12. Insert the pin through the hole in the two bosses to lock them together. The button on the end of the pin must be depressed to insert it in the hole.
13. If the Handling Fixture is to be moved with the dewar, leave the two pins that lock the ears on the dewar to the Handling Fixture in place to keep the fixture locked to the dewar so both can be picked up by the crane; if not, remove the gear shield on the Handling Fixture by loosing the four screws and sliding it up and off, and also remove the two pins in the fixture.
14. Adjust the sling by sliding the eye to the position that will keep the dewar horizontal. This can be done by lifting slightly with the handling device on the crane and seeing which end tries to sink and then slacking off and moving the eye slightly to that end of the sling wire and trying again. WARNING: Do not shock the dewar when lowering it into the fixture.
15. The dewar can now be hoisted by the crane.
16. Remove the two handling fixture ears from the dewar, the one with the gear and the one with the bearing sleeve. Each is held with 4 captive socket head screws that require a 1/4 inch hex wrench.
17. Attach the ears to the handling fixture with the pins and replace the gear cover.
18. Remove the Handling Fixture from the dewar if it is attached (See above).
19. Check that the dewar mounting plate it properly attached to the module.
20. Rotate the Forward Cass IR Module so that the bay to receive the dewar is straight up.
21. If the 4 knurled screws on the Installation Fixture cross bars have been previously properly set and locked, leave them as is, otherwise fully extend them downward.
22. Fully contract the adjusting fixture mounted to the crane.
23. Position the dewar above the module so that it is properly positioned over the bay.
24. Using the adjusting fixture on the crane lower the dewar so that the mounting end, the ears and the bar at the window end of the dewar are all captive in the bay.
25. Connect any hoses and cables that must be connected before the dewar is fully installed. DO NOT connect any level shifter or preamplifier electronics cables. The dewar is not necessarily well grounded.
26. Using the slowest crane motion, lower the dewar until it is within the range of the adjusting fixture attached to the crane of being seated. If the range is small the adjusting fixture should be contracted when the dewar is part way down.
27. Use the adjusting fixture on the crane to lower the dewar until the mounting plate and dewar are engaged. NOTE: If the 4 knurled screws were previously properly adjusted and locked, the dewar will be full engaged with the mounting plate and resting on the two knurled screw head near the window of the dewar. The two other screw heads near the mounting end of the dewar should be tight against the uprights of the frame. The intent is that when the dewar mounting bolts are tightened, the window end of the dewar should rise slightly, about .1 inch, so that the installation fixture is free enough that the pin holding it to the dewar can be extracted by pressing down on the end of the fixture opposite the hook. The bars are springs to take up shock of lowering into the bay and to prevent the dewar from intruding into another instrument's space.
28. If the knurled screws have not been adjusted then back them off bit by by bit as the dewar is being lowered.
29. When the dewar is in the proper position slack off on the fixture several inches with the crane.
30. Turn off the crane. WARNING: When the mounting bolts are engaged the crane can do serious damage to the instrument and module.
31. Tighten both spring loaded captive 1/2 inch mounting socket head bolts to 200 to 500 in/lbs of torque with a 3/8 hex wrench.
32. Remove attachment pin from center boss on Installation Fixture and put it in the hole on the top of the fixture. The pin is released by holding in the center button on its end. It might be necessary to put a downward force on the window end of the fixture to free the pin.
33. Turn on the crane.
34. Lift the fixture so that the pin end can be disengaged from the hook on the dewar. Watch out for the sockets on the electronics boxes and also for the extending ears on the fixture.
35. Hoist the fixture clear and store the fixture and sling.
36. Connect all remaining cables and hoses, and fasten them properly so that they cannot hang up when the module is installed or rotated in the telescope.

NIRC Removal

1. Turn off all electrical power to the dewar, electronics, motors, and heaters.
2. Unplug and clear all accessible cables and hoses to the dewar.
3. Cap all accessible sockets on the dewar.
4. Rotate the IR module so that the bay with the dewar is straight up.
5. Prepare crane with precision handling device (Hydroset) in its fully contracted position. Hook Installation Fixture by its adjustable wire sling to precision handling device on crane.
6. Adjust sling so that the end of the Installation Fixture with the movable ears is about 10 inches above the end with the cross bolt.
7. Check that the attachment pin is out of the center boss and in the 1/2 inch hole in the top of the fixture.
8. Position the fixture above the dewar with the ears around the window end and the cross pin of the fixture just in front of the dewar hook by the electronics boxes. The pin is released by holding the pin shoulder between the index and middle fingers and pushing in the button on the end with the thumb. This retracts the ball on the other end allowing the pin to be extracted.
9. Watching for the socket caps slide, the cross bolt into the hook on the dewar.
10. While keeping the bolt in the hook, lower the fixture with the crane until the boss in the middle bottom of the fixture goes around the mating boss on the dewar. This might take force on the window end of fixture to bend the crossarms that push on the module posts so that the pin can be pushed into the boss.
11. Turn off the crane. WARNING: When the attachment pin is in the boss, the crane can do damage to the dewar and the module if it is raised.
12. Insert the pin through the hole in the two bosses to lock them together. The button on the end of the pin must be depressed to insert it in the hole. Check that the adjusting screw heads are firmly against the module posts. WARNING: These screws stop the module from intruding on the other instrument spaces when the mounting bolts are loosened.
13. Loosen both spring loaded captive 1/2 inch socket head mounting bolts that with a 3/8 hex wrench. Make sure that they both are disengaged!
14. Turn on the crane.
15. Again make sure both mounting bolts are disengaged from the mounting plate.
16. Set the precession adjusting fixture on the crane to its fully extended position.
17. Move the eye on the adjustable sling to the nominal position on the cable for lifting the dewar horizontally.
18. Take up all but a little of the slack in the sling with the slow motion of the crane.
19. Lift the dewar slightly with the precession adjusting fixture.
20. Check to see that it is free and balanced horizontally.
21. If it is not horizontal, lower the dewar with the adjusting fixture and move the eye on the sling toward the low end of the dewar and then try again.
22. When the dewar is horizontal and free lift it only high enough to disconnect the remaining hoses. The ears and end bar of the Installation Fixture and the dewar should still be captive in the frame.
23. With the dewar now completely detached from the module, lift it using the slow of the crane till it is completely free of the module.
24. Position the dewar over the Handling Fixture.
25. Remove the gear cover from the handling fixture by loosing the 4 knurled screws and sliding the cover up and off.
26. Remove the pin that holds the gear attachment to the Handling Fixture post and let it hang by the chain.
27. Screw the gear to the boss on the side of the dewar using a 1/4 inch hex wrench to tighten the 4 captive screws.
28. Do the same with the sleeved bearing on the other side of the Handling fixture.
29. Contract the precession lifting device on the crane.
30. Lower the dewar with the slow motion of the crane until it is to within about 3/4 inch of being seated in the Handling Fixture posts.
31. Use the precession lifting device to lower the dewar the rest of the way into the Handling Fixture. Check to see that the gear engages with the worm as the dewar is lowered.
32. Insert both pins in the hole in the posts and reinstall the gear cover.
33. The dewar and Handling Fixture can now be moved with the crane if desired. If this is done use the precession lifting device to finally place the load back on the ground to eliminate shock to the dewar.
34. To remove the Installation Fixture, remove the attaching pin in the central boss of the fixture.
35. Lift the Installation fixture with the slow motion to the crane until the window end is about 10 inches higher than the other end.
36. Slide the cross bolt of the fixture out of the hook on the dewar, taking care not to damage the electrical sockets.
37. Lift the fixture clear with the crane.
38. Detach the Installation Fixture with the sling from the crane and store.