Downloaded from https://www.everyspec.com MIL-STD-1311D METHOD 1121 BASE STRAIN (Miniature tube) 1. Preparation. Prior to testing, all tubes shall be subjected to a pin-straightening procedure. For this immersion test, the water container shall be sufficiently large so that no TUT is closer than .750 inch (19.05 mm) from the container sides. The vessel used shall have a minimum capacity of 2 liters per 15 tubes, and shall be at least 75 percent full for every strain test to insure a more uniform temperature gradient for all TUT.
The holders for simultaneous testing at least fifty percent of the tubes in the sample at one time, shall provide sufficient spacing between the pins of the adjacent tubes so that the tubes do not contact each other. A minimum of six, .375 inch (9.53 mm) diameter holes shall be made in the plate of each holder. Align the axis of each tube with the axis of the deflection cone (see Drawing 200-JAN), and carefully push the small end of the cone into the circle formed by the pins until firm contact is made against the tube header. 2. Procedure. Submerge the holder with tubes in place into the container of boiling water (97 ° C to 100 ° C).
The tubes attached to cones shall be completely submerged. After 10 seconds' submersion, remove from water, place on a nonmetallic support, and allow to cool at room temperature. If after removal of tubes from the cones, examination reveals some pins are bent more than others, the test has been improperly conducted. 3. Alternate test. Submerge the holder with tubes in place into a container of cool water (20 ° C to 30 ° C) for 5 seconds, followed immediately by a dip in boiling water (97 ° C to 100 ° C) for 10 seconds which is in turn followed by an immediate dip in cool water for an additional 10 seconds, then remove and allow to dry. 4.
Testing shall be performed within approximately 1 hour after the exhaust operation during manufacture. Upon completion of the test, tubes shall be examined for the following defects. The class of strain-test defects shall be in accordance with the following tabulation: Defect Class Envelope or tip cracks (or both) Button (wafer-header) cracks Seal cracks A B C METHOD 1121 1121-1 19 April 1968