1、1-1 MIL-STD-1441A (EA) 28 June 1994 SUPERSEDING MIL-STD-IMl(MU) 3 June 1968 M ILITARY STANDARD EQUIPMENT, LEAK DETECTION, HELIUM, FOR CHEMICAL MUNITIONS AMSC N/A FSC 4925 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Provided by IHSNot for ResaleNo reproduction or
2、 networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) FOREWORD 1. This Military Standard is approved for use by all Departments and Agencies of the Department of Defense. 2. Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in imp
3、roving this document should be addressed to Technical Director, U.S. Army Edgewood Research, Development and Engineering Center, Attn: SCBRD-ENE (STD/SPECS/PKG), Aberdeen Proving Ground, MD 21 O1 0-5423, by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appeari
4、ng at the end of this document or by letter. 3. This standard is approved for use by all Departments and Agencies of the Department of Defense in the selection of equipment to determine leaks in chemical munitions. ii Provided by IHSNot for ResaleNo reproduction or networking permitted without licen
5、se from IHS-,-,-MI L-STD-1441 A (EA) CONTENTS Paraaraph PaGe 1 . SCOPE 1 1 . 1 Scope 1 1.2 Classification 1 2 . APPLICABLE DOCUMENTS (Not applicable) . 2 3 . DEFINITIONS 3 3.1 Definitions of Technical Terms 3 3.1 . 1 3.1.2 Helium Leak Detector . 3 Mass Spectrometer . 3 4 . GENERAL REQUIREMENTS . 4 4
6、.1 Description 4 4.2 Construction . 4 5 . 5.1 5.1 . 1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1 -7 5.1.8 5.1.9 5.1.1 O 5.1.1 1 5.1 . 12 5.1 . 13 5.1.14 5.1 . 15 5.2 DETAILED REQUIREMENTS . 5 Design criteria 5 Equipment 5 Leakdetector 5 Pumping equipment 5 Control panel 5 Worktable . 5 Monitoring . 6 Handlin
7、g 6 Contamination prevention . 6 Production requirement . 6 Detection cycle 6 Instrumentation 6 Cleaning 6 Safety of personnel . 6 Finish and nameplate 7 Manuals 7 Circuitry . 5 iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-1441A (EA) C
8、ONTENTS Paraaraph Page 6 . NOTES 8 Submission for approval . 8 Shipment and Storage 8 Subject term (key word) listing . 9 Changes from previous issue 9 6.1 Intended use 8 6.2 6.2.1 Excessive cost of equipment due to production requirements 8 6.3 6.4 Technical assistance 8 6.5 6.6 iv Provided by IHSN
9、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) 1. SCOPE 1 .I Scope. This standard covers various types and classes of helium leak detection equipment for use in testing the inert components of chemical munitions for leaks, and also the final clo
10、sure containing the chemical fill. -. s ing types and classes: 1.2 Classification. Helium leak detectors covered by this standard shall be of the follow- - - New leak detectors built for specific applications Rebuilt Government-furnished leak detectors, modified for specific applications For final c
11、losure of all munitions in the filling line Sniffer type to locate leaks to be reworked Type I Type II Class 1 - For heavy-walled munitions Class 2 - For thin-walled munitions Class 3 Class 4 - - 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MI L
12、-STD-1441 A (EA) 2. APPLICABLE DOCUMENTS (Not applicable to this document) 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) 3. DEFINITIONS 3.1 Definitions of Technical Terms. 3.1 .I Mass spectrometer- A mass spectrometer is an in
13、strument used to separate and determine the relative abundance of ions of different mass to charge ratio. Operation of the mass spectrometer depends on the deflection of ionized components of elements, compounds or mixtures, created by bombarding a sample in the gas phase with a beam of high-energy
14、electrons. The high-energy electrons knock one electron from a sample molecule, producing a singly charged positive ion referred to as the parent ion. This ion in turn fragments to form a variety of other fast-moving positive ion fragments, mainly sin- gly charged, which are stable only in the gas p
15、hase under the high-vacuum conditions used. These ions are directed through a magnetic field, which deflects their paths to an extent dependent upon their mass-to-charge ratios. The ions with the lowest mass-to- charge ratio are deflected the most. By varying the magnetic field, ions of any mass-to-
16、 charge ratio can be made to strike the detector. Since the ions are principally singly charged, the separation is primarily on the basis of mass. Taking into account the magnetic field and other characteristics of the instrument, the mass-to-charge ratio can be deter- mined and hence the mass of ea
17、ch fragment. A mass spectrum is determined by (1) vary- ing the magnetic field so that ions with progressively higher masses strike the detector, and (2) plotting the relative intensities (proportional to the numbers of ions of particular masses), as indicated by the detector, versus their mass-to-c
18、harge ratios. The mass-to- charge ratio of the parent ion is the molecular weight of the molecule. Therefore the mass spectrometer provides one of the best methods for obtaining very accurate molecular weights. More than that, however, the pattern of fragmentation and the masses of the par- ent ion
19、and of each fragment ion provide an excellent “fingerprint method for identifying the compound. 3.1.2 Helium leak detector. A helium leak detector is a mass spectrometer adjusted to detect helium gas. It can be used with a probe of helium to explore the outside of a system to detect a leak from insi
20、de a system, or it can be used inside a system to check for leaks from outside. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MI L-STD-1441 A (EA) 4. GENERAL REQUIREMENTS 4.1 Description. The equipment shall be capable of detecting helium leakage
21、 using a helium type mass spectrometer. The method used shall be placing the munition in a hood or chamber and evacuating either the interior of the munition or the chamber surrounding the munition. Helium shall be introduced into the space surrounding the munition or into the munition whichever is
22、applicable. If any leaks are present, helium will bedrawn through the leak into the evacuated space and then to the leak detector. The equipment shall be identified for acceptance or rejection in accordance with the requirements specified herein. 4.2 Construction. The equipment shall be ruggedly con
23、structed for full time production operation. It shall be capable of three-shift operation, eight-hours per shift. Regardless of type, the pumps shall be of sufficient capacity to complete a test cycle which will satisfy the requirement of 5.1 .I O. 4 Provided by IHSNot for ResaleNo reproduction or n
24、etworking permitted without license from IHS-,-,-MI L-STD-1441 A (EA) 5. DETAILED REQUIREMENTS 5.1 Desian criteria. The equipment described by this standard is intended to be used in production to screen components, determine leaks in filled munitions, and to conduct surveillance of existing stocks.
25、 The variety of components and the differences in the vol- umes and configurations of various munitions, dictate in part that pump-down time re- quired will vary for each test cycle. There will be cases where the requirement of 5.1.1 O cannot be met except at excessive costs for large pumps and othe
26、r equipment. (See 6.2.1 ) 5.1.1 Equipment. The equipment shall be in sections: leak detector (mass spectrome- ter), pumping equipment, control panel, and a worktable with necessary manifolding and valves. The worktable is the only item to be specifically designed for the munition to be tested. The o
27、ther items may be capable of being transferred from one operation to another. Vinyl tubing shall be used wherever flexible tubing is required. Rubber is not acceptable. 5.1.2 Leak detector. The leak detector shall be a helium mass spectrometer with a dy- namic sensitivity of at least 1 O-7 cubic cen
28、timeters per second (cc/sec) at one atmosphere pressure differential with all external pumps running. In order to obtain this capability, the maximum sensitive capability will be approximately 1 O-9 cc/sec with all external pumps shut down. This sensitivity is required in order to obtain reliable re
29、adings at 10-6 cc/sec, which is the sensitivity required in production. 5.1.3 Pumpina equipment. Evacuation of the items under test, or the chambers sur- rounding them, shall be accomplished with mechanical and/or diffusion vacuum pumps as necessary to reduce pressure to 20 microns of mercury or les
30、s. 5.1.4 Control panel. A control panel shall be provided, and will contain all switches, indi- cator lights, and gages except those specifically required on the worktable. The worktable shall be connected as closely as possible to prevent lag in readings and promote maximum sensitivity. 5.1.5 Workt
31、able. The worktable portion of the helium leak detection system may be part of the production line. This section of the production line will be considered part of the he- lium leak detection equipment and if the latter is retained by the Government it will be part of the equipment retained. It shall
32、 also contain the required manifolding and valves. 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) 5.1.6 Circuitry. The programming and control portion may consist of electronic equip- ment or electromechanical equipment. With t
33、he exception of start-stop switches and the master power switch, the sequential operation of the equipment shall be fully automated. (Fully automatic handling of test items is not necessarily implied here.) However, each step in the operation cycle shall be capable of being held by a manual override
34、 switch. The leak detector shall provide for automatic indication in case of current failure to the spectrometer portion of the detector, and shall be so interlocked that tests cannot be conducted in the event of such failure. Munitions which have a leak rate of 1 O+ cc/sec or greater, or in which a
35、 leak is so gross as to prevent evacuation to a pressure of 20 microns of mercury shall be indicated by a red light on the control panel. Munitions which do not have a leak as great as 1 O4 cc/sec shall be indicated by a green light on the control panel. A yellow indicator light shall remain on unti
36、l the start of the next test. Any munition which exceeds the leakage limit shall be automatically marked, or in some manner identified in order to prevent its in- clusion in the regular lot. 5.1.7 Monitorinq. The equipment shall be checked for sensitivity and accuracy by means of a “calibrated glass
37、 leak“, permanently attached to the vacuum system. It shall be in the order of magnitude of lo4 atmospheric cc/sec. The sensitivity check shall be made at the start of each shift, and every 2 hours thereafter. Should an out-of*alibration condition be found, the items checked prior to this finding sh
38、all be rechecked in reverse order back to the last known acceptable item. 5.1.8 Handling. The contractor shall provide the mechanical equipment which will ac- complish the required handling of the test items immediately before, during, and immedi- ately after the execution of helium leak test. This
39、handling shall not damage the test items; nor shall it alter their appearance or condition in any way which may affect the intended use of the items. 5.1.9 Contamination prevention. The mass spectrometer shall have a built-in cold trap for trapping water, oil vapors and condensable gases. It shall a
40、lso have an external cold trap to prevent condensable vapors from entering the master equipment. The helium equipment shall be placed in a closed area to prevent contamination. The test items must be clean both inside and outside to prevent contamination of the test equipment. Small amounts of conta
41、mination not visible to the eye may cause wear of the pumping units which will cause a shut-down. The venting of the helium detection equipment and the munitions will be to a space outside the closed area, preferably outdoors. 5.1.1 O Production requirement. The mass spectrometer must be able to det
42、ect leaks at a rate at least 30 percent greater than the anticipated production rate. 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) 5.1 .I1 Detection cycle. The time of exposure of the item to the helium leak test shall be in
43、accordance with the instruction manual furnished for the test equipment. The pres- sure in the space being tested for the presence of helium shall not exceed 20 microns of mercury prior to the beginning of the detection cycle. During the cycle, the helium used shall be at a pressure differential of
44、not less than one atmosphere. The “helium atmo- sphere” shall contain not less than 95 percent helium during the detection cycle, except for Class 4. This requirement may be obtained by purging. 5.1 .I2 Instrumentation. The instruments which indicate directly for the operator must respond quickly en
45、ough to keep the operator fully informed of the progress throughout the test cycle. 5.1.1 3 Cleaninq. The manifolding and other equipment shall be so constructed and ar- ranged as to facilitate cleaning where contaminates collect on the interior surfaces. 5.1 -1 4 Safety of personnel. All exposed mo
46、ving parts of the equipment, such as drive belts, etc., shall be equipped with safety guards, and any other potentially dangerous conditions shall be also labelled. 5.1 .I5 Finish and nameplate. The finish shall be commercial standard for this type of equipment. The nameplate shall contain as a mini
47、mum, the power requirements and the vacuum capacity. 5.2 Manuals. Each piece of new equipment and each piece of modified equipment shall be provided with new operating and maintenance instruction manuals. They shall contain complete information for installation, operation and maintenance, and shall
48、also include technical literature from the supplier of components. The manuals shall list the items that the equipment is capable of testing, and the production rate for each item. The number of manuals to be provided shall be specified in the contract. 7 Provided by IHSNot for ResaleNo reproduction
49、 or networking permitted without license from IHS-,-,-MIL-STD-1441 A (EA) 6. NOTES (This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.) 6.1 Intended use. This standard contains requirements for the design of a helium leak detector to be used to determine whether a chemical munition is leaking. 6.2 Submi
