1、Designation:D 2539 93An American National StandardStandard Test Method forShock Sensitivity of Liquid Monopropellants by the Card-Gap Test1This standard is issued under the fixed designation D 2539;the number immediately following the designation indicates the year oforiginal adoption or,in the case
2、 of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 In considering the handling properties of a liquid pro-pellant,serious consideration is given to
3、the possibility ofhazard initiated by hydrodynamic shock.The consequences ofsuch a shock may include:(1)nonpropagating explosion,(2)propagating but low-velocity detonation,and(3)propagatinghigh-velocity detonation.All three are hazards;the test de-scribed herein is useful for one hazard only,namely
4、propagat-ing high-velocity detonation.1.2 This standard should be used to measure and describethe properties of materials,products,or assemblies in responseto heat and flame under controlled laboratory conditions andshould not be used to describe or appraise the fire hazard orfire risk of materials,
5、products,or assemblies under actual fireconditions.However,results of this test may be used aselements of a fire risk assessment which takes into account allof the factors which are pertinent to an assessment of the firehazard of a particular end use.1.3 This standard does not purport to address all
6、 of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 The values stated in SI units are to be regarded as thestandard
7、.The values given in parentheses are for informationonly.2.Summary of Test Method2.1 This test method gives an evaluation of the sensitivity ofa high-energy liquid propellant in terms of a stack of plasticcards inserted between a sample of liquid and a standardbooster charge of high explosive.The se
8、nsitivity value is takenas the number of cards required to attenuate the booster shockjust enough that the liquid detonates in 50%of the trials.Foran unknown liquid,15 to 25 shots(requiring up to 1000 mL ofliquid)can be needed to define its sensitivity value.Because ofthe destructive nature of the t
9、est,a sufficient supply ofexpendable parts must be available before a sensitivity deter-mination is attempted.2.2 The card-gap test described is a measure of the hydro-dynamic shock required to produce a stable,high-velocitydetonation in a 1-in.standard steel pipe.Because of the largesample size sub
10、jected to this detonability test,the test is not tobe done in the laboratory.The advantages of the card-gap testare its practical scale,reproducibility,and moderate materialcost.The interpretation of results of the test is a matter ofconsiderable judgment.While a propellant may show a lowsensitivity
11、 in the card-gap test,this does not preclude thepossibility of other dangers.On the other hand,a very highcard-gap sensitivity does not always preclude the usability ofsuch a liquid propellant,since it is possible that suitableengineering design can incorporate preventative measuresagainst propagati
12、on of detonation.It is known that the degreeof confinement,size,and material of the container,amongother parameters,influence detonation propagation;therefore,the results of any specific test may be highly apparatus-dependent.NOTE1Gap tests for determining explosive sensitivity are new.Atechnique of
13、 using paper cards for the gap materials and steep pipe forcontainers was developed in England at the Explosives Research andDevelopment Establishment.The version described herein is essentiallythe Naval Ordnance Laboratory modification.The test is valuable becauseit yields reproducible data and it
14、has been found that results of differentinvestigators show close agreement.3.Significance and Use3.1 The property measured is the tendency of a propellant toundergo a high-order detonation when subjected to a givenhydrodynamic shock.One limitation of the test is the difficultyof applying it to mater
15、ials under conditions where the vaporpressure exceeds 1 atm.3.2 The test is valuable because it yields very reproducibledata,and it has been found that results of different investigatorsshow close agreement.4.Apparatus4.1 CupThe liquid under test is held in a cylindrical steelcup,closed at the botto
16、m by a thin,flat diaphragm.It shall befabricated as follows(Fig.1):1This test method is under the jurisdiction of ASTM Committee F-7 onAerospace Industry Methods and is the direct responsibility of SubcommitteeF07.02 on Propellant Technology.Current edition approved March 15,1993.Published May 1993.Originallypublished as D 2539 66 T.Last previous edition D 2539 70(1980).This test method is identical in substance with the Card Gap Test for ShockSensitivity of Liquid Monopropellants recommended by