Downloaded from https://www.everyspec.com MIL-STD-2031(SH) i!. Oxygen. Commcncc oxygen flow, adjust for an overall Ilow rate 1S lilers/minu!e on the ITA module. Select the 100 percen[ range cm the oxygen analyzer panel meter. . Aller a short time. [he slciidv rcii(!iny should k- 100 rwrumt: lhc DVM should also DVM. Cease oxygen tlow. The ~i~librii[iorr of [hc osygcn analyzer and adjustment of the DVM readout are now complete. The DVM will register oxygen concentrations between 0-100 percent. RglSt Cr 1~) pCrCCnl. A(iJUSl as rcqulrcd 10 unsulc’ ;Igrecr]lcr]l on tt)c panel meter and 40.4 Determination of oxygen index nt ambient temperature.
Determination of oxygen index at ambient temperature shall include the follnwing: a. Atmosphere. Remove the chimney and place (he specimen in the specimen holder. Replaee the chimney and allow 30 seconds for the system to purge and establish the atmosphere surrounding the specimen. b. l~ition. Ignite the top of the specimen with the flame of an appropriate burner. Usually, a standard 14 ounce (OZ) propane cylinder with narrow flame tip is used as the ignition source. When the specimen is WCII lit, remove the burner and start the timer to record burning time. c. Ctiretitr. Observe the burning of the specimen.
If the specimen bums longer than 3 minutes or burns beyond a length of 50 millimeters (mm), the oxygen concentration is too great and must be reduced. Select either criterion; time or bum length, depending upon the behavior of the mRterini, ., d. Cafctdmbrts. Once the proper mixture of oxygen and nitrogen has been obtained, 5 to 10 specimens shttll be tested, to permit calculation of an averttge value of the oxygen index for the material under examination. 40.5 Determination of oxygen index nt elevated ternperatnre.
Determinations at elevated temperatures are carried out in the same manner as the ambient temperature measurements except that the wmbination of the ITA and HIWA modules shall be used and the H~A overall gas mixture flow rates may be varied with operating temperature to achieve constant flow veloeity in the column surrounding the specimen. 40.5.1 Gas flow rote. The gas flow rate shall be adjusted to correspond to the desired initial oxygen index and test temperature. For submarine composite materials, three temperatures shall be of interest 25, 75 and 300%2 (75, 165 and 570 ‘F).
The corresponding flow rates shall be 9.7, 8.3, and 5.1 Iitem/minute for a 4 centimeter per seeond (cm/s) flow vebeity. The flow of the oxygen-nitrogen mixture shall be halted and the air pump shall be started, with appropriate flow rate adjustment. The preheater and column heater controls shall be adjusted in accordance with the manufacturers instructions to attain the desired test temperature. When the test temperature has been reached, the air pump shall be shut off and oxygen-nitrogen flow shall be re-established.