Intro

To increase liquid Nitrogen hold times on the LRIS red and blue side dewars the stingers can be removed and the instrument rotated with the dewars at the 12 o'clock position. This increases the capacity of Nitrogen the dewars can hold. With this configuration the dewars should hold Nitrogen to at least 24 hours.

Tools required:

Tool Location
LRIS dewar stinger installation/removal tool Nas deck instrument drawer
Teflon washers available Instrument lab LRIS shelf
Short dewar stinger (~3.5 inches) Blue dewar/nas deck drawer
Long dewar stinger (~4.5 inches) Red dewar/nas deck drawer

For a picture of the stingers and tools see the images section below.

Removal

  1. Rotate LRIS to fill position.
  2. Insert stinger tool into neck of dewar.
  3. Maneuver tool to insert into stinger retaining slot.
  4. Rotate counter-clockwise until loose.
  5. Pull stinger straight out of dewar.
  6. Verify Teflon washer intact.
  7. Rotate LRIS dewars to 12 o'clock position and fill with LN2.
  8. Add note to telescope status white board "LRIS stingers out: no EL moves; no instrument rotation"
  9. Disable and tag out CASS rotator in AAA.

Installation

  1. Enable CASS rotator in AAA.
  2. Rotate LRIS to fill position.
  3. Insert stinger and stinger tool into dewar neck.
  4. Rotate clockwise until snug.
  5. Back off (counter-clockwise) about 1/4 turn.
  6. Remove stinger tool.
  7. Rotate LRIS dewars to the 6 o'clock position.
  8. Verify no drips or leaks from dewar neck. You may adjust stinger with tool at this position.
  9. Rotate LRIS to fill position if no leaks and fill with LN2.
  10. Remove telescope status white board note and AAA tag out.

Images

Below is an image of LRIS with the rotator at the correct position for filling with LN2. At this position, the cryo will last the longest. This is the position for Removal step #7.


Below is an image of LRIS with the rotator at the correct position for removing and inserting the stingers. Corresponds to steps Removal #1 and Install #2.


Below: Extraction tool and the stingers


Below Extraction tool inserted into the stinger