Downloaded from https://www.everyspec.com MIL-STD-81OD 19 July .1983 A-1.2.1.5 ~ and circulation sv#&_m. A system shall be provided for the mixing of air and fuel .toproduce flammable air-vapor.mixtures, and for the circulation into the test chamber of the mixtures so produced. The system shall consist of a closed-duct circuit o f which the test chamber shall form a part. The circuit shall be equipped with a mixing blower capable of producing an air velocity in conformance with the performance limits of A-1.3.3 below. An additional blower of similar capability shall be provided to insure thorough circulation,of air-vapor mixtures within the test chamber.
The system shall be equipped with valves to permit safe and practical scavenging of the test chamberand test.item, and to bring in outside air for mixing. The outside incoming air port should be equipped with a drying chamber which contains silica gel or some other drying agent: An air bypass system shall also be connected to the downstream side of the drying chamber through a control valve and into the chamber, to permit air to be bled into..the chamber during a test run. The complete injection and mixing operation shall require not more than 3 minutes. ., ,. ‘A-1.2.1.6 E!@ meter~ Svstern.
A means shall be provided whereby fuel vapor can be metered into the mixing and circulation system in controlled quantities to produce explosive mixtures of any desired air-vapon ratio. A-1.2.1.7 Fue1 vaDO&. A vaporizer shall be provided in the mixing and circulation system to ‘vaporizeliquid fuel for mixing with air. The vaporizer should consistofl a heat exchanger using water as an exchange media. The water shall be heated by itmnersiontype heaters in order to warm the mixing air Prior to initial contact between the air and the atomized fuel from the fuel injectors. A-1.2.1.8 Et@osion rellef valvm.
., Three presgure relief valves (see an ‘exampletype in figure 1) shall be provided for the size chamber described ‘herein. The valves shall be designed to open at the minimum chamber operating pressure and, when opened by an explosion, shall remain in that position until released. Closure should.be either by manual actuation of hand valves or by automatic preesure equalization”of the test.area and the.surrounding atmosphere through suitable restrictive orifices. Each valve shall have a minimum cross- iectional area of O.13 square meters (200square inches). :.. A-1.2.1.9 ELI.& The explosion facility shall be capable of utilizing n-hekane fuel to produce flammable vapor mixtures.
A.1.2.1.1O .J@&.@I svsterq. An ignition system shall be provided to permit ignition of the atmospheres within the main chamber, the sampling chamber and the case of the test item, as required. This shall be accomplished by spark plugs installed in appropriate locations within the chamber and with leads provided ‘forplugs installed in test item cases. Spark plugs shal1 be positioned so as to eliminate any effect by wall conditions on spark temperature. . . ttiTHOD511.2 APPENDIX 1. 19 July 1983 511.2-13