Inspect MRS twice a year.

When was the last time you checked the tritium-powered muzzle reference sensor (MRS) on that tank, mechanic?

If you didn't do it during the last semiannual PMCS, it's been too long. Here's what to do:

Look through the inspection window. You should see a blue light. If not, the tritium power cell could be damaged and may be leaking inside the MRS. Double-wrap the MRS in plastic and notify your support.

Take a closer look at the inspection window on top of the MRS. If the window is loose or cracked, or if condensation has formed on the underside of the window, the MRS could be leaking tritium gas. Double-wrap the MRS in plastic and notify your support.

Don't Forget the Desiccant

Both the tritium- and electronic-powered MRS use desiccant to absorb excess moisture. Replace that desiccant semiannually, or more often in high humidity areas.

Here's how:

1. Wear the latex gloves that come with the desiccant kit, NSN 1240-01-424-4628, to protect yourself against potential leaks from a tritium-powered MRS.

2. Use a 3/8-in socket-head screw key to remove both pipe screws on the barrel of the MRS.

3. Remove the old O-rings.

4. Unwrap a new desiccant, NSN 6850-01-081-4193, and use it to push the old desiccant out of the barrel hole.

5. Install two new O-rings, NSN 5331-00-724-7902, onto the pipe screws. Torque the screws between 240-250 lb-in.

            Tritium MRS     Battery, EMRS
  Tank      NSN 1240-01-    NSN 1240-01-

M1/IPM1       324-2217        475-0278
              275-0077
              409-0784
M1A1          380-3125        475-0276
              276-6628
              313-8932
M1A2 SEP      444-6558        475-0275
              356-5887