1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1988 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTJ1267REAF.DEC88Issued 1979-05Reaffirmed 1988-12Supersed
4、ing J1257JUN84LEAKAGE TESTINGForewordThis Reaffirmed Document has not changed other than to put it into the new SAE Technical StandardsBoard Format.1. ScopeThis information report provides basic information on leakage testing, as applied to nondestructivetesting, and affords the user sufficient info
5、rmation so that he may decide whether leakage testing methodsapply to his particular need. Detailed references are listed in Section 2.2. References2.1 Applicable PublicationsThe following publications form a part of the specification to the extent specifiedherein. Unless otherwise indicated the las
6、test revision of SAE publications shall apply.2.1.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAEJ426Liquid Penetrant Test Methods2.2 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of thi
7、s document.2.2.1 ASTM PUBLICATIONSAvailable from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM E 425Standard Definitions of Terms Relating to Leak TestingASTME427Recommended Practice for Testing for Leaks Using the Halogen Leak Detector (Alkali-IonDiode)ASTM E 432Standard Recomm
8、ended Guide for the Selection of a Leak Testing MethodASTM E 479Standard Recommended Guide for Preparation of a Leak Test SpecificationASTME493Standard Test Methods for Leaks Using the Mass Spectrometer Leak Detector in theInside-Out Testing ModeASTME498Standard Methods of Testing for Leaks Using th
9、e Mass Spectrometer Leak Detector orResidual Gas Analyzer in Tracer Probe ModeASTME499Standard Methods of Testing for Leaks Using the Mass Spectrometer Leak Detector in theDetector Probe ModeASTM E 515Standard Methods of Testing for Leaks Using Bubble Emission TechniquesASTM E 908Standard Practice f
10、or Calibrating Gaseous Reference LeaksSAE J1267 Reaffirmed DEC88-2-2.3 Other PublicationsNondestructive Testing Handbook, Volume 1, “Leak Testing,“ 1982, American Society for NondestructiveTesting, Columbus, OH 43228.J. W. Marr, Leakage Testing Handbook, 1968, NASA Cr-952, Jet Propulsion Laboratory,
11、 NationalAeronautics and Space Administration, Washington, DC.N. I. Sax, Dangerous Properties of Industrial Methods, 2nd Edition, 1963, Reinhold Publishing Corp., NewYork, NY.J. W. Perry, Chemical Engineering Handbook, 3rd Edition, 1950, McGraw-Hill Book Co., New York, NY.Metals Handbook, 8th Editio
12、n, Volume 11, 1976, pp. 260-270, American Society for Metals, Metals Park,OH 44073.ASME Boiler and Pressure Vessel Code, latest addenda, American Society for Mechanical Engineers,New York, NY.Qualification and Certification of Personnel, Recommended Practice SNT-TC-1A, Supplement G (LeakTesting), Am
13、erican Society for Nondestructive Testing, Columbus, OH 43228.R. J. Roehrs, Leak Testing of Welded Vessels, 2nd Annual Symposium on Nondestructive Testing ofWelds, sponsored by IITRI, Chicago, IL, 1967.3. GeneralLeakage testing is a form of nondestructive testing capable of determining the existence
14、 of leaksites and, under proper conditions, measuring the quantity of material passing through these sites. The wordleak means the hole through which fluid (liquid or gas) passes in either a pressurized or evacuated system,while leakage is the term used to connote the mass flow of fluid regardless o
15、f the size of the leak. Leakagerate is the quantity of fluid per unit time that flows through the leak at a given temperature as a result of aspecified pressure difference across the leak. The ASTM accepted unit of leakage rate is standard cubiccentimeters per second (std. cm3/s), frequently referre
16、d to as atmosphere cubic centimeters per second (atm.cm3/s). The SI terminology is Pascal cubic meters per second (Pa m3/s). (1 Pa M3/s = 10 atm. cm3/s,approximately.)There is no container in which a differential pressure exists (either pressurized or vacuum) that does not leak tosome extent. Absolu
17、te leak tightness is an absolute impossibility. Any container must, therefore, have amaximum leakage rate specified. In considering the leakage rate that can be tolerated, one must decidewhether the rate represents the total leakage from the system or the maximum leakage from a single leak.Additiona
18、l factors to be considered include shelf life, product contained, toxicity, legal requirements,consequences of excessive leakage, cost of product, cost of testing, and customer requirements. Once aleakage rate has been specified then a leak test procedure describing the operating and test conditions
19、 needsto be detailed. Since leakage rate relates pressure, volume, and time, more than one set of procedural valuescan yield the same leakage rate. In general, the pressure used should reflect pressures that the item wouldsee in service, however, this is not a requirement. In some isolated cases, us
20、ing markedly different pressurescan cause leaks to pass grossly different rates of fluid due to elastic deformation of the item being tested.Regardless of the type of leakage testing being done, safety considerations for the personnel performing thesetests must be a paramount consideration.SAE J1267
21、 Reaffirmed DEC88-3-4. Principles There are eight or more primary methods which may be employed to detect, locate, and/ormeasure leakage. The following paragraphs identify these methods and describe their principles, as well astheir capabilities and limitations.4.1 Mass Loss and Pressure ChangeThese
22、 are two related methods. Traditionally, these are used for sizableleakage rates, and provide no information as to the leak site. Mass loss is calculated on the basis of change inmass at two times; accordingly, extremely accurate weighing is a requirement of this method. Pressurechange methods opera
23、te in a similar fashion, except that a change in pressure is the signaling mechanism.Pressure change systems usually measure change of the gaseous systems. Since pressure is temperaturedependent, the temperature of the system must either remain constant or be compensated for by use of idealgas laws.
24、 Mass loss and pressure change methods, using most techniques, are time consuming and thus arelimited in leakage testing applications.Theoretically, these methods are very accurate if one has sufficient time to conduct the test.4.2 Ultrasonic Leak TestingThis is a method valuable for detecting leaka
25、ge great enough to produce turbulentflow. Turbulent flow in a gas occurs when the velocity approaches the speed of sound in that gas; this isapproximately 101 to 102 std. cm3/s. This method takes advantage of the fact that turbulent flow generatessound frequencies from audible upward to 60 kHz. In u
26、sing only the ultrasonic component generated, fewerfalse signals are detected because there are fewer other sources of ambient ultrasound. Because of the highlydirectional nature of ultrasound, the leak can usually be accurately located. Output of ultrasonic leak detectorsis an audible signal or a m
27、eter deflection, the strength of which is a function of the leak rate. Advantages of theultrasonic method are that the equipment is simple to operate, it can be done with the probe removed from theleak, and it does not require any material which could clog a leak and require cleaning. Its primarydis
28、advantage lies in its lack of sensitivity to small leakage rates (less than 102 std. cm3/s).4.3 Chemical Penetrant Leak TestsThese are incapable of providing leakage rate information, but do clearlypoint out sites for repair. Sensitivities are generally conceded to be in the range of 103 std. cm3/s,
29、 althoughgreater sensitivities have been achieved. Two basic forms of chemical penetrants are available, liquid tracers(quite similar to liquid penetrants, see SAE Information Report J426) and gaseous tracers. Hydrostatic testingwith water alone is not a substitute for leakage testing.4.3.1 LIQUID T
30、RACERSLiquid tracers are usually a solution of a tracer dye and a liquid in which it is soluble. It isessential to determine the coloring power of the tracer solution in the concentration being used as this relatesto the sensitivity, as does the wettability of the tracer solution. As a general rule
31、in white light systems, basicdyes work best in a water solution and solvent dyes are better suited to an oil based system. White lightliquid tracer systems are generally inferior to fluorescent liquid tracer systems. This sensitivity inferiority isdue, in part, to the increased visibility of fluores
32、cent dyes, and the inherent contrast of the dyes to the nearblack background used in testing. By dissolving a fluorescent tracer in a volatile liquid, very small leaks canbe found, because the liquid which evaporates leaves behind a concentrated dye which is more visible.Advantages of liquid tracers
33、 lie in their cost, sensitivity, and ease of use. Foremost among theirdisadvantages is that they use material which could temporarily clog a leak. Also, liquid tracers requirecleaning of the parts after use and care in their application so as not to create false signals. In addition, onemay experien
34、ce occasional difficulty in tracing large leakages to their source due to liquid spread.4.3.2 GASEOUS TRACERSGaseous tracers are gases which color indicating media, thereby denoting the locationof a leak. The most widely used gas for this application is ammonia. Indicating media for ammonia gas are:
35、1. Phenolphthalein which turns from clear to pink.2. Bromocresol purple which turns from a yellow-green to purple.3. Bromothymol blue, which turns from yellow to blue.Carbon dioxide gas can be used for leak testing with an indicating medium of sodium carbonate andphenolphthalein in an agar-agar solu
36、tion. This bright red indicator will turn white at a leak site.SAE J1267 Reaffirmed DEC88-4-There is another medium, which is much less widely used, due to the inherent danger of its chemicals.Pressurizing a component with ammonia and then allowing hydrogen chloride to be brought near, willproduce a
37、 white cloud of ammonium chloride vapor which is clearly visible. These gases are highly corrosiveand dangerous to human tissue. Extreme care and a high level of ventilation are needed, as well asconsideration for the safety of the personnel performing the test.There is little difference in the leve
38、l of sensitivity for gaseous tracers when compared to liquid tracers; bothare typically at 103 std. cm3/s. Rates as low as 106 std. cm3/s have been reported for gaseous tracers.Primary among their advantages is their low cost of operation since no instrumentation is needed.Disadvantages are that som
39、e gases could corrode the test object, be hazardous to personnel, requirecleanup, and clog leaks.4.4 Bubble Leak TestThese methods are widely used. They possess sensitivities to a commercial range assmall as 104 std. cm3/s (102 is a practical value for an unskilled operator). In the laboratory, unde
40、r idealconditions with special combinations of liquid and gas, rates as low as 107 std. cm3/s have been detected.The method operates on the basis of a differential pressure at a leak creating a flow of gas. This gas, uponescaping, will produce one or more bubbles in the test liquid. These bubbles ma
41、rk the location of the leak andthe frequency and size can be used to estimate the leakage rate.Procedurally, the test object is fixtured and pressurized, and then the indicating liquid (not a soap or detergentsolution) is brought into contact with the component. This precludes the liquid from tempor
42、arily blocking asmall leak which could cause the acceptance of a leaking component. Precleaning of the test object isnecessary because surface contaminants also may cause a temporary blockage of a leak. From a practicalstandpoint, any gas may be used to pressurize the object. Should air be used, it
43、must be very clean, again topreclude temporary blockage of a leak. Shop air is generally too dirty, wet, and oily to use for leak testing.Ample illumination must be provided to permit the inspector to be able to see a stream of bubbles; 1000 1m/m2(100 fc) is recommended as a minimum level.Indication
44、 of leakage may be accomplished by the use of:1. A liquid in which the test object is immersed.2. A liquid film which produces bubbles when a leakage passes. (A vacuum box which surrounds the testarea may be used to create the pressure differential.)Liquids used in bubble testing must not corrode th
45、e object being tested. Frequently, it is desired to enhancethe sensitivity of a bubble test. Enhancement can be done by increasing the time for testing or increasing thepressure. In some instances, neither of these approaches is practical. Changing the gas to one of a lowermolecular weight and/or lo
46、wering the surface tension of the liquid will also enhance the sensitivity. Visualinspection should be conducted at distances less than 0.6 m (2 ft) for best results.A vacuum box places an area to be tested under a sub-atmospheric pressure. A clear window through whichobservations are made and a liq
47、uid in which leakage appears are necessary for the vacuum box technique.When used (usually for welds in large vessels) adjacent testing locations must be overlapped to assure fullcoverage.The advantages of bubble testing lie in its simplicity, cost, and relative sensitivity. Disadvantages include th
48、eneed for cleanup, the fact that fine leaks may not be detected due to a lack of time, the possibility of clogging,and finally that bubble testing is a visual inspection, and as such, bubble testing is limited by the performanceof an operator.SAE J1267 Reaffirmed DEC88-5-4.5 Thermal Conductivity Lea
49、k Testing These methods have a minimum leakage rate detectability of 105 std.cm3/s. They are based on the principle that certain gases have a markedly different thermal conductivity whencompared to air. Equipment for this method consists of two heated filaments in a bridge circuit. One filamentis cooled by air and the other by the test gas. Any differences unbalance the bridge and can be related toleakage. The two gases with the greatest difference in thermal conductivity are hydrogen and helium. Mostthermal conductivity leak testing is done with argon, CO2,
