MIL-STD-202H.pdf - 第95页

MI L - S TD - 202 - 112 T ABL E I I . T es t pr e s s ur e a nd dur at i on f or c ondi t i on F . T es t pr es s ur e D ur at i on 75 p s i g . 5 hr 60 p s i g 1. 0 hr 30 p s i g 2. 5 hr 15 p s i g 12. 5 hr T A B L E II…

MIL-STD-202-112

4.7.2 Apparatus.

4.7.2.1 Chamber. A vacuum/pressure chamber capable of the evacuation and subsequent pressure bombing of

devices up to 75 psig and maintaining pressure up to 12.5 hours.

4.7.2.2 Filter. A filtration system capable of removing particles greater than 1 micron in size from the fluorocarbon

fluid.

4.7.2.3 Detector. A fluorocarbon vapor detection system with a nominal sensitivity of 10

-5

atm cm

/s. The

sensitivity of the detector shall be better than 14 micrograms of FC84 or D/80. The detector shall have a linear

response to 280 micrograms and a response time of better than 1 second.

4.7.2.4 Instruments. Suitable calibrated instruments to indicate that test, pressure times and temperatures are as

specified. The detection system shall be calibrated using a calibration source of fluorocarbon at least once each shift

to an accuracy of at least ±15 percent.

4.7.3 Precautions. The following precautions shall be observed in conducting the fluorocarbon gross leak test.

a. Fluorocarbons shall be filtered through a filter system capable of removing particles greater than 1

micrometer prior to use. Bulk filtering and storage is permissible. Liquid that has accumulated observable

quantities of particulate matter during use shall be discarded or reclaimed by filtration for re-use.

Precautions shall be taken to prevent contamination.

b. Precautions should be taken to prevent operator injury due to package rupture or violent evolution of bomb

fluid when testing large packages.

4.7.4 Procedure. The devices shall be placed in a vacuum/pressure chamber and the pressure reduced to 5 torr

or lower and maintained for 30 minutes minimum. A sufficient amount of FC-84 or D/80 detector fluid shall be

admitted to the pressure chamber to completely cover the devices. The fluid shall be admitted after the 30 minute

minimum vacuum period but before breaking the vacuum. The devices shall then be pressurized in accordance with

table II. Upon completion of the pressurization period, the pressure shall be released and the devices removed from

the pressure chamber without being removed from the detector fluid for more than 20 seconds. When the devices

are removed from the fluid for testing, they shall be air dried for a minimum of 20 seconds and a maximum of 5

minutes prior to the test cycle. The devices shall then be tested with a fluorocarbon vapor detector in accordance

with the system operating instructions and as follows. Devices shall be admitted to the purge chamber and purged

(heated to remove any remaining surface fluorocarbon and to initiate vaporization of any internal fluorocarbon fluid).

Purge time shall be in accordance with table III. Test time shall commence immediately after purge either in the

same chamber (single chamber system) or an adjoining test chamber (dual chamber system). Test time shall be a

minimum of 3.5 seconds (unless the device is rejected earlier) with the fluorocarbon vapor detector purge and test

chambers at a temperature of 125°C ±5°C or 2.5 seconds minimum with the purge and test chambers at 150°C ±5°C.

During test time, the amount of fluorocarbon outgassing is measured and the total integrated value is compared to

the alarm level.

NOTE: Air dry, purge, and test time limits for each device shall be complied with in all cases, whether the device is

handled individually or in plastic or metal tubes.

4.7.4.1 Failure criteria. A device shall be rejected if the detector instrumentation indicates more than 280

micrograms of fluorocarbon gas.

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MIL-STD-202-112

TABLE II. Test pressure and duration for condition F.

Test pressure Duration

75 psig .5 hr

60 psig 1.0 hr

30 psig 2.5 hr

15 psig 12.5 hr

TABLE III. Purge time for condition F.

Package with internal

free volume (cm

)

Purge time 1/

(seconds)

≤ 0.01

3 1/3-5

>0.01 ≤0.10

6-9

>0.10 8 2/3-13

1/ With purge chamber at 150°C, minimum and maximum

purge times should be reduced by 1/3.

NOTE: If necessary, due to device construction or materials, maximum purge time can be determined by cycling a

device with a 0.02 to 0.05 inch diameter hole and measuring the maximum time that can be used without permitting

the device to escape detection during the test cycle.

4.8. Measurements. Upon completion of the test, measurements shall be made as specified.

5. DETAILED REQUIREMENTS

5.1 Summary. The following details are to be specified in the individual specification.

a. Test condition letter (see 4.1.1).

(1) For test condition C.

(a) Procedure number and accept and reject leak rate.

(b) Backfilling pressure when verification of seal is required (see 4.4.3, 4.4.4.1 and .4.4.2).

(d) For procedure IV.

1. Reduced pressure of the chamber and duration of pressurization (see 4.4.4.4).

2. Whether perforation of specimen is required (see 4.4.4.4).

(e) For procedures III and IV.

1. Applicable gross leak conditions.

(2) For test conditions D and E.

(a) Test mounting fixtures (see 4.5.4 and 4.6.4).

1. Measurements after test (see 4.8).

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MIL-STD-202-112

6. NOTES

(This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.)

6.1 Supersession data. The main body and 38 parts of this revision of MIL-STD-202 replace superseded MIL-STD-

202.

Custodians: Preparing activity:

Army - CR DLA – CC

Navy - EC

Air Force - 85 (Project 59GP-2015-016)

DLA - CC

Review activities:

Army - AR, AT, AV, CR4, MI, SM, TE

Navy - AS, OS, SH

Air Force - 19, 99

NSA - NS

NOTE: The activities listed above were interested in this document as of the date of this document. Since

organizations and responsibilities can change, you should verify the currency of the information above using the

ASSIST Online database at https://assist.dla.mil/

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