ASTM_D_2540_-_93.pdf

Designation:D 2540 93Standard Test Method forDrop-Weight Sensitivity of Liquid Monopropellants1This standard is issued under the fixed designation D 2540;the number immediately following the designation indicates the year oforiginal adoption or,in the case 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 This test method2covers the determination of thesensitivity of liquid monopropellants to the impact of a dropweight.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,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 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.The values given in parentheses are for informationonly.2.Summary of Test Method2.1 A small sample of the liquid(0.03 mL)to be tested isenclosed in a cavity(0.06 mL)formed by a steel cup,an elasticring,and a steel diaphragm(see Fig.1).A piston rests on thediaphragm and carries a vent hole which is blocked by the steeldiaphragm.A weight is dropped onto the piston.A positiveresult is indicated by puncture of the steel diaphragm accom-panied by a loud noise or severe deformation of the diaphragmand evidence that the sample was completely consumed.Thesensitivity value for a given sample shall be expressed as theheight from which the specified weight is dropped for theprobability of explosion to be 50%.3.Significance and Use3.1 In drop-weight testing of liquids,explosions are initi-ated in a complex compression process involving the degreeand rate of pressurization,the thermodynamic gas properties,heat transfer,hydrodynamic properties,etc.At this time,thefundamental significance of the test cannot be exactly defined.The test is considered useful,however,as a rapid and simplemeans to rate sensitive liquids as to their relative explosivesensitivity.Since it requires only a few grams of sample,it canbe an important laboratory tool to determine the handlingsafety of new materials before substantial quantities are pre-pared.3.2 Tests in which the sample volume is varied(at constantcavity volume of 0.06 mL)show that the degree of fillingaffects the result.Note that the relationship between sensitivityrating and sample volume is not a characteristic of the testapparatus but is a function specific to each propellant.At 50%filling(0.03 mL of sample),the dependency of sensitivity onsample volume is moderate so that the error in sample volumemeasurement has a negligible influence.Tests show that thedelivered sample volume is reproducible to 60.5%whenmeasured by a fixed-stroke syringe,and 0.03 mL shall be thestandard sample volume.3.3 If the objective justifies the greater effort,the samplevolume is varied leading to a plot such as shown in Fig.2which represents the relationship between sensitivity rating andsample volume for the specific propellant n-propyl nitrate.1This test method is under the jurisdiction of ASTM Committee F-7 onAerospace Industry Methods and is the direct responsibility of SubcommitteeF 07.02on Propellant Technology.Current edition approved March 15,1993.Published May 1993.Originallypublished as D 2540 66 T.Last previous edition D 2540 70(1982)e1.2This method is identical in substance with the JANNAF method,“Drop WeightTest,”Test Number 4,Liquid Propellant Test Methods,May 1964,published by theChemical Propulsion Information Agency,Johns Hopkins University,AppliedPhysics Laboratory,Johns Hopkins Rd.,Laurel,Md.20810.FIG.1 Sample Cup Assembly1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.4.Apparatus4.1 Sample Cup AssemblyThe sample cup assembly isshown in Fig.1,and an exploded view in Fig.3.The assemblyshall consist of the following parts:Part No.Name1body2cup3O-ring(expendable)4diaphragm(expendable)5piston6ball7capSince the sample cup assembly is the critical part of thedrop-weight tester,detailed dimensions of its components aregiven in Fig.4.4.2 WeightThe weight shall be one integral assembly,weighing 2 kg 6 1 g(Fig.5).The weight shall be heldsuspended by an electromagnet.The electromagnet shall itselfbe held in the first version of the drop-weight tester by a studat the top which fits in the recess formerly designed to hold andrelease the weight.The rele