A-1.2.1.10 Ignitionvstem. An ignition system shall be erovlded to pert iAiition of the atmospheres wdthin the main chanber, the saspling chamber and the oase of the test item, as required. This ahall be acconplished by spark plugs Installed in appropriate locations wdthin the chanber and with leads provided for plugs Inatalled in test item cases. Sperk plugs shall be positioned so as to eliminate any effect by wall conditions on spark tesperatia.

tETHyD 511.3 APPEMDix Д

A-1.2.1.5 Mixing and circulation system. A ayatrnm shall be provided for the mxlng of air and fuel to produce flannable air-vapor mixtures, and for the circulation into the test chan±>er of the mixtures so prodijced. The system shall consist of a closed-duct circuit of which the test chanber shall form a part. The circuit shall be equipped with a mixing blower capable of producing an air velocity in conformance with the perfornsjice limits of А-1.3.Э. An additior.al blowar of similar capability shall be provided to insure thorough circulation of air-vapor mlxtiB>as rtthin th test chamber. The system shall be equipped wiith valves to permit safe and practioal scavenging of the test chanber and test item, and to bring in outside air for mixing. The outside incoming air port should be equipped with a drying chanber which contains silica gel or some other drying agent. An air bypass system shall also be connected tc the downstream side cf the drying chaaber throt a control valve and into the chanber, to permit air to be bled into the chanber during a test rui. The coaplete injection and mixing oijeraticMi shall require not more than 3 minutes.

A-1.2.1.6 Fuel metering svsteaa. A means shall be provided whereby fuel vapor can be metered into the mixing and circulation system in controlled quantities to

produce explosive mixtures cf any desired а1г-У1!фог ratio.

A-1.2.1.7 Fuel vaporizer. A vaporizer shall be provided in the mixing and circulation system to vaporize liquid fuel for mixing wdth air. The vaporizer should consist of a heat exchanger using water as an exchange media. The wmiter shall be heated by immersion type 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 Explosion relief valves. Three pressts relief valves (see an exanple type in figure Al) shall be provided for the size chanber described herein. The valves shall be designed to open at the mininun chanber operating pressure and. when opened

by an explosion, shall remain in tbat position uittil released. Closure should be either by staniial actuation of hand valves or by automatic ртеввиге equalization ef the test ал>еа and the surrouxiing atmosphere through suitable restrictive orifices. Each valve shall have a minimum crown-sectional area of 0.13 square meters (200 square inches).

A-1.2.1.9 Fuel. The explosion facility shall be capable of utilizing n-hexane fuel

tc prcduce flaamable vapor mixtin es.

A-1.2.1.11 Electrical system. All electrical conponents of this facility shall be explosionproof and conform to the applicable portion of the National Fire Underwriters Code. The chamber shall be equipped with sealed male plugs and female jack feedthroughs to transmit power as required through the chancer wail to the item under test. For exanple:

12 - 150 ащр. jack aurid plxjg terminals

12-75 arrp. jar-k and pliig terminals

12 - 40 anp. jack and plug terminals

12 - 10 amp. jack and pltjg terminals (male jack and female plug)

Studs may be used through the chamber well provided they are wired to jacks located on a panel mounted on the facility. Jacks and plugs should be similar to and interchangeable with existing laboratory equipment.

A-1.2.1.12 Vacuum putod. A vacuum punp capable of producing and maintaining within the test chamber any desired pressure altitude within the performance limits specified in A-i.3.2 shall be provided. The punp shall be mounted on the sane

chassis as the chamber. Five minutes shall be the rnaxinum al Icwable time to produce any pressure altitude desired.

A-1.2.1.13 Sanp 1 ing. .chamber. A sanpling chamber equipped with a blower and a spark plug shall be provided. The blower shall be capable of mixture circulation at the velocity specified in A-1.3.3 and shall be appropriately located. The volume of the sanpling chamber shall be not less them 1 cubic foot and the configuration symnstrical, to prevent end effects resulting from ignition of explosive mixtures. The sanpling charnber shall be of a strength equal to that of the main test chanjber. A maximum pressure indicator shall be furnished for the sampling chamber. The sampling chairber shall be external to the main chamber but in as close proximity thereto as possible. The inlet side of the sanpling chamber mixing blower shall be provided with a flexible probe mich can be placed in the vicinity of any potential arcing sources on ths test item. Provision should be made to insure that sanpling chamber wall temperature will be equal to r in chaniber 11 tenperature.

A-1.2.1.14 Heater system. A thermostatically regulated heater system capable of controlling the air tenperature in the chamber within perfomance limits specified in A-i.3.4 shall be provided. The heater system shall be built into the chanber walls so that the chansber air tenpe-ature ts controlled by heat frcra the walls. The time required to att-ain any desired tenperature shal 1 not exceed one hour. Tenperature fluctuations due to the introduction into the test chaniber of air-vapor mixtuD>es shall not exceed S.SC (10.0°F) in magnitude nor two minutes in duration.

A-1.2.1.15 Inatrunents. Tbe following instrumente shall be provided:

a. Altinsstsr 0-25.000 asters (0-80.000 feet)

b. kfaxinuB pressure indicator (2) 0-24(Ю pascals (0-350 psi)

c. Chaaber air tenperature indicator 0-280 (0-500K)

d. Chanber wrall tenperature indicator 0-200°C (0-500°F)

e. Fuel tenperature indicator 0-40°C (0-100**F)

f. Vxjrizer air tenperatis indicator 0-200<C (0-5(X>)

g. Vaorirer media tenperatxjre indicator 0-260®C (0-500®r)

h. Fuel quantity gage (calibrated for n-hexane of 0.650 specific gravity at 20°C relative to water at A°C and reading in milliliters of fuel)

i. Fuel inert pressijre indicator 0-700 kPa (6.76 psia) J. Heater thermostat 0-2eO°C (0-500°F)

A-1.2.1.16 Controls. The facility shall be provided with switches, valves, etc. for control of all components and systems of the test chamber. Controls shall be )

ncunted so that their use is convenient.

A-1.2.1.17 Safetv provisions

A-1.2.1.17.1 Indicator liiuts. Panel-mounted individual lights shall be provided and Installed on the test facility in a location readily visible to tbe operator, each light being indicative of the status or condition of a system or piece of equlpoent not in an observable position. All coixlltlons Involving operational safety

shall be so indicated and any others will be included if specified by the prccurir.g activity.

A-1.2.1.17.2 Safety interlock systems. An automatic mechanical or electrical interlock device shall be provided to prevent the premature actuation of the ignition system. The design of the system shal I be шме'Л that al 1 openings to the main test chamber, inoluding the mm.in door, the explosion relief valves, ths circulation system inlet and outlet ports, and the sanpllng chaaber ports, nust be securely closed before energy can be transmitted form the ignition system to the spark plugs. An audible signal shall be provided to sound If actuation of the ignition system is attenpted before all the above listed chanber vents are closed.

A-1.2.1.17.3 ExaerAencv presaure relief device. A rupture disk or other suitable type of faist acting pressure relief device shall be provided. The device shall be designed to rupture or otherwise relieve, when subjected to a pressure in excess of the chamber design pressure. The pressure relief device shall be located on top of the test chanber and protected by a vented dome to prevent fragmentation hazard.

A-1.3 Performance

A-1.3.1 Chaniber desito pressure. The test chamber shall be capable of vnthstaiiding any explosion pressxjre up to and including 2 msgapascals (300 pound per square inch).

A-1.3.2 Pressure altitude. The chanber shall be capable of maintaining any desired pressure altitude from sea level to 18.250 meters (0-60.000 feet) within the limits specified in A-1.3.2.1.

А-1.Э.2.1 (ДмшЬег leakage. With the vacuum pump turned off, the chanber shall be capable of maintaining any pressure altitude from sea level to 3000 meters (10.000 feet) for a period of 10 minutes, and any altitude from 3000 meters (10,000 feet) to 18,000 meters (60.000 feet) for a period of 20 minutes, with a loss not to exceed 5 percent of the total pressure altitude during either time.

A-1.3.3 Blower air velocity. The blowers enployed for mixing and circulation of air-vapor mixtures within the mixing circuit, the main chanber and the sanpling chanber shall be capable of producing outlet air velocities between 300 and 600 meters per minute (1.0(Ю and 2,000 feet per minute).

A-1.3.4 Caianber..air .temperature. The air tenperature within the test chanber shall be controllable between 20°C and 240°C ±3°C (70**F and A50°F) at all points 1-1/2 inches or further from the chanber walls. Within the 20°C to the 120°C (70°F to 250°Ю tenperature range, no hot spots in excess of 40°C (75°F) over the thermostat setting shall exist in the chanber atmosphere. For the 1200 to 240 (250 to 450F) tenperatxire range hot spots in excess of 15C (25°Ю above the thermostat setting are not permissible in the chanber atmosphere. Time required to raise the anbient air tenperatwe from 20°C (70*F) to any desired value within the specified range shal 1 not exceed 60 minutes.

A-1.3.5 Tolerances

A-1.3.5.1 Instrunents and controls. Unless otherwise specified, instrunents and controls shall be accurate within the following limits:

a. Tenperature indicator (including thermostats): *\°C (+2°F).

b. Pressure indicator: *5 kPa (+.1 psi) .

c. Altimeter: +.1 percent.

d. Thermostat: +.1°С {+2<=1?) .

A-1.3.5.2 Environments. Unless otherwise specified, environmental conditions induced within the chairber shall not vary in excess of the following limits:

a. Air or mixtiire velocity; 1.5 percent (in meters per minute)

b. Altitudes: ±2 percent (in meters).

c. Tenperature: +3°C [*G°F). NOTES:

1. Intended use. The explosion-proof testing chanber described herein is intended for use in the acconplishment of explosion-proof tests in accoiiance with this standard.

2. Instruction manvial. An instruction manual should be available to provide the following information concerning the explosive atmosphere test chanber:

a. Op)erating instructions.

b. Maintenance instruction.

c. Assembly and disassembly procedure.

d. List and description of all replaceable parts.

e. Detailed assenbly dramngs.

f. Wiring diagram.

3. Faci 1 itv capabi 1 itv data. The following information should be stanped on data plates, 4iich should be attached to the test facility at the location specified:

a. Maximum chanber design pressure: By chanber pressure indicator.

b. Vaporizer mixing air velocity: By vaporizer control switch.

c. Outlet air velocities of blowers: On side of test facility in a clearly visible location.

d. Emergency relief pressure: On dome of emergency pressure relief device.

e. Identification by name and purpose of each instrunent, control, or indicating light: On or near the item concerned.

f. Explosion relief valve minimum opening pressure: On base of middle valve.

METHOD 511.3 itFPcInDIX A

. Free-volimB (in cubic f##t) of main and sanpling chairbers: Or. sides of chanbers.

4. Facility calibration charts and <iata. Calibration charts and other data should be ayailable as follove:

a. Calibration chart to correct the fuel quantity gage for use with fuels of other than the gravity for which the gage was originally calibrated.

b. (Jallbration chart for altimeter.

c. Calibration charts for correction of scale error of various indicators.

METHOD 511.3 АРРОШХХ A

№7ГдаО 512.3 LEAKAGE (IVNEBSIOK)

PAGE

SECTION I

I-l PURPOSE......................512.3-1

1-2 EMVITONMENT-AL EFFECTS...............512.3-1

1-3 GUIDELINES FOR DETERMINING TEST

PROCEDURES AND TEST CONDITIONS .......... 512.3-1

1-4 SPECIAL CONSIDERATIONS...............

1-5 REFERENCES ..................... 512.3-5

SECTION II

II-l APPARATUS ..................... 512.3-6

11-2 PREPARATION FOR TEST................ 512.3-6

11-3 PROCEDURES ..................... 512.3-7

11-4 INFORMATION TO BE RECORDED............. 512.3-8

SECTION I

I-l PURPLE. Leakage (imnerslon) tests are conducted to determine whether materiel is constructed so that it can be inmersed in water without leakage of the water into the enclosure.

1-2 ENVIBONIITMj EbKliCTS. Penetration (seepage) of water into equipment enclosures can result in ргоЫепв such as:

a. Fouling of lubricants between moving pkarts.

b. Formation of electrically conductive bridges which may cause electronic equiiMnent to malfunction or become unsafe to operate.

c. Corrosion due to direct exposure to ths water or to ths relatively high humidity levels caiaed by the water.

d. Diminishment of the burning qualities of explosives, propellants. fuels, etc. 1-3 СТЛРШ.1№5 FOR РетШДШШ TEST PRQCmuRES AJTO TEST С0НР1Т10Ш

NOTE: The tailoring process as described in section 4 of this document should be used to determine the appropriate tests and test variables.

a. Appl ication. This method is used when the test item is designed to be watertight and may be exposed to partial or conqplete immersion in water. This test may, in some cases, be used to verify watertightness in lieu of a rain test, provided that the test item configuration is the same and erosion is not a problem.

b. Reatriction. This method does not necessarily duplicate serviee eonditions but is used to verify the integrity of the test items seals. Ininersion tests are not to be used lor buoyant items ш1€яя the life cycle profile identifies specific application with restraints that could hold the materiel under water.

c. Sequence. (See General Requirements, 5.1.4) This test should be performed before and after structural tests such as shock and vibration to aid in determining

the test items watertightness after dynamic tests.

d. Test variations. This method consists of one test procedure with several related test conditions that mList be given values before the test is initiated, such as:

(1) Test item configuration.

(2) Preheat tenperature.

(3) Depth of inmersion.

(4) Duration of ininersion.

(5) Additional guidelines aa appropriate. 1-3.1 Choice of test procedure

a. Teat objectives. The primary objectives of the leakage (ininersion) test are

to determine wether:

(1) The test item can be inmersed in wetter vithout penetration of the % ater into the test item.

(2) The penetration of any water into the test item will cause operational degradation of the test item.

(3) The test item can be operated safely following immersion.

(4) Other possible effects may be caused by water leaking into the test

item.

Based on this information and the pvs>pose of the test item, determine any variations

to the basic test that are required.

b. Procedure I,- Basic leakage. Thia procediire is used to test relatively small test items (man-packed or man-portable for the most part) that employ seals or gaskets to prevent water penetration into the interior. 1/

\J Shelter-size test itens nay be subjected to the fording testing of MIL-S-5528e or MIL-S-55541.

1-3.2 Choice of related test conditiona

a. Test.item configuration. The configuration of the test item is an irportant factor affecting water penetration into the test item. The following are exanples of configurations to consider:

Cl) In a shipping/storage container or transit case.

(2) Sealed with protective covers, cps, plugs, etc.

(3) Mbdified with kits for special applications.

(4) Normal operating configuration.

b. Conditioning. This test usual ly Includes heating of the test item to induce expansion of naterials and. after cooling, to establish a pressure differential to determine viiether the seals or gaskets leak under relatively low pressure.

(1) A pressure differential is created between the inside and outside of the test item fol lowing imnersion by heating the test item to a tenperature of 27°C

(or 49**F) above the water tenperature.

(2) The tenperature of the water s.hall be 18° llOC (64° llSF) .

(3) Duration. The test item shall be heated ijntil tenperature stabilization of the test item has occurred or for two hours, lAichever occurs first (a sufficient time to raise the internal air tenperature to a

value approaching 45C).

c. Depth of imniBrsion. The depth of imnersion affects the pressure differential that develops on the test item. Since this method is designed to test the effectiveness of seals or gaskets, a 1-meter test depth is suggested. This, combined with the initial test item tenperature, should result in twice the pressure differential of imnersion to Im without heating. Other values such as those shovn in table 512.3-1 may be used if appropriate.

d. Duration of imnersion Just as the test item is heated for at least two hours before imnersion to Insiire thorough heating, the imnersion period of two hours is considered adeq\jate to develop leakage if it is to occur.

€. Add 11ioria 1 guide 1 inss. Review the equlpnent specification and r-equiremsnts docunents. Apply any additional guidelines necessary.

1-4 SPECIAL CONSIDERATIONS

1-4.1 Fai lure.analysis. Based on the Individual test time and the requirement for its leakage resistance, the following failure criteria apply: