ASTM D2540-93
(Test Method)Standard Test Method for Drop-Weight Sensitivity of Liquid Monopropellants
Standard Test Method for Drop-Weight Sensitivity of Liquid Monopropellants
SCOPE
1.1 This test method covers the determination of the sensitivity of liquid monopropellants to the impact of a drop weight.
1.2 This standard should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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Designation: D 2540 – 93
Standard Test Method for
Drop-Weight Sensitivity of Liquid Monopropellants
This standard is issued under the fixed designation D 2540; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of the
sensitivity of liquid monopropellants to the impact of a drop
weight.
1.2 This standard should be used to measure and describe
the properties of materials, products, or assemblies in response
to heat and flame under controlled laboratory conditions and
should not be used to describe or appraise the fire hazard or
fire risk of materials, products, or assemblies under actual fire
conditions. However, results of this test may be used as
elements of a fire risk assessment which takes into account all
of the factors which are pertinent to an assessment of the fire
hazard of a particular end use.
1.3 This standard does not purport to address all of the
safety problems, if any, associated with its use. It is the
responsibility 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 the FIG. 1 Sample Cup Assembly
standard. The values given in parentheses are for information
only.
ated in a complex compression process involving the degree
and rate of pressurization, the thermodynamic gas properties,
2. Summary of Test Method
heat transfer, hydrodynamic properties, etc. At this time, the
2.1 A small sample of the liquid (0.03 mL) to be tested is
fundamental significance of the test cannot be exactly defined.
enclosed in a cavity (0.06 mL) formed by a steel cup, an elastic
The test is considered useful, however, as a rapid and simple
ring, and a steel diaphragm (see Fig. 1). A piston rests on the
means to rate sensitive liquids as to their relative explosive
diaphragm and carries a vent hole which is blocked by the steel
sensitivity. Since it requires only a few grams of sample, it can
diaphragm. A weight is dropped onto the piston. A positive
be an important laboratory tool to determine the handling
result is indicated by puncture of the steel diaphragm accom-
safety of new materials before substantial quantities are pre-
panied by a loud noise or severe deformation of the diaphragm
pared.
and evidence that the sample was completely consumed. The
3.2 Tests in which the sample volume is varied (at constant
sensitivity value for a given sample shall be expressed as the
cavity volume of 0.06 mL) show that the degree of filling
height from which the specified weight is dropped for the
affects the result. Note that the relationship between sensitivity
probability of explosion to be 50 %.
rating and sample volume is not a characteristic of the test
3. Significance and Use apparatus but is a function specific to each propellant. At 50 %
filling (0.03 mL of sample), the dependency of sensitivity on
3.1 In drop-weight testing of liquids, explosions are initi-
sample volume is moderate so that the error in sample volume
measurement has a negligible influence. Tests show that the
This test method is under the jurisdiction of ASTM Committee F-7 on
delivered sample volume is reproducible to 60.5 % when
Aerospace Industry Methods and is the direct responsibility of Subcommittee
measured by a fixed-stroke syringe, and 0.03 mL shall be the
F 07.02on Propellant Technology.
standard sample volume.
Current edition approved March 15, 1993. Published May 1993. Originally
e1
published as D 2540 – 66 T. Last previous edition D 2540 – 70 (1982) .
3.3 If the objective justifies the greater effort, the sample
This method is identical in substance with the JANNAF method, “Drop Weight
volume is varied leading to a plot such as shown in Fig. 2
Test,” Test Number 4, Liquid Propellant Test Methods, May 1964, published by the
which represents the relationship between sensitivity rating and
Chemical Propulsion Information Agency, Johns Hopkins University, Applied
Physics Laboratory, Johns Hopkins Rd., Laurel, Md. 20810. sample volume for the specific propellant n-propyl nitrate.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2540
at the top which fits in the recess formerly designed to hold and
release the weight. The release shall be tied down to hold the
magnet firmly in place. The present magnet plus weight shall
be of such a length that the scale on the right hand post will
read the correct drop height.
4.2.1 In using this weight, constant vigilance shall be
maintained to see that the weight tip does not become
excessively worn or damaged. If excessive wear is indicated
the apparatus should be rechecked on a standard sample.
Damaged weights should be discarded.
4.3 Drop-Weight Assembly (Fig. 6), consisting of a base
plate with four leveling screws; column; two guide rods (one
graduated); body retainer; release mechanism, adjustable to
retain magnet; and top plate.
4.4 Tools, consisting of a torque wrench, 0 to 1.7-N·m (0 to
15-lb·in.) torque wrench adaptor to fit cap (part 7 of Fig. 4);
hypodermic syringe of fixed stroke; O-ring seating tool; brass
pick; and spanner wrench.
FIG. 2 Impact Sensitivity, H , of NPN versus Sample Volume at
50 4.5 Expandables, such as O-rings: either AN 6227B-5 or
70°F (21.1°C) Using a 2-kg Weight
6.076 0.13-mm (0.239 6 0.005-in.) inside diameter and
1.78-mm (0.070-in.) cross section width, made from MIL-P-
4. Apparatus
5516 elastomer, or both; and diaphragms of Type 302 stainless
steel 0.41 6 0.013 mm (0.016 6 0.0005 in.) thick, 9.22 mm
4.1 Sample Cup Assembly—The sample cup assembly is
(0.363 in.) in diameter.
shown in Fig. 1, and an exploded view in Fig. 3. The assembly
shall consist of the following parts:
5. Safety Precautions
Part No. Name
1 body
5.1 A positive safety latch shall be provided to prevent
2 cup
3 O-ring (expendable)
injury resulting from the premature fall of the weight. It is
4 diaphragm (expendable)
realized that this test might be employed for the evaluation of
5 piston
ultra-high-energy materials. This fact, combined with the
6 ball
7 cap
possibility of faulty fabrication of components, could result in
the production of shrapnel. It is therefore recommended that
Since the sample cup assembly is the critical part of the
the apparatus be shielded (Fig. 7).
drop-weight tester, detailed dimensions of its components are
given in Fig. 4. 5.2 If the test apparatus is to be employed for the evaluation
4.2 Weight—The weight shall be one integral assembly, of toxic materials, or if toxic products may be formed from the
weighing 2 kg 6 1 g (Fig. 5). The weight shall be held decomposition of the sample, necessary steps shall be taken to
suspended by an electromagnet. The electromagnet shall itself prevent the buildup of dangerous concentrations of these
be held in the first version of the drop-weight tester by a stud materials.
FIG. 3 Sample Cup Assembly, Exploded View
D 2540
FIG. 4 Sample Cup Assembly, Detailed View
6. Preparation of Apparatus check the exhaust hole and ports of the piston to be sure they
are clear of the blown out section of the diaphragm. Note the
6.1 Experience has shown that an appreciable difference in
condition of the pistons and cups. Replace cracked, pitted, or
the behavior of the apparatus can result from the manner in
worn components.
which it is mounted. Therefore, the following conditions shall
be met:
NOTE 1—For temperature uniformity and speed of operation, it is
6.1.1 The machine shall be mounted on and firmly attached
recommended that a separate cup and piston be used for each test in a
to a solid concrete foundation, preferably anchored to the series. This also ensures that possible cup damage will not affect the
results of subsequent tests in the series.
foundation of the building.
6.1.2 The machine shall be perfectly plumb with guides
7.1.2 Set the height by loosening the locking handle that
lubricated to minimize friction during the fall of the weight.
binds the release mechanism to the support column, and sliding
6.2 The drop-weight sensitivity of sensitive liquids is, or
the mechanism until the height indicator is properly aligned
course, dependent on the purity of the sample. The magnitude
with the graduated guide rod. Tighten the locking handle and
of this dependency will vary with the material. If attempts are
set the safety latch.
being made to reproduce data obtained by other investigations,
7.1.3 Place an AN 6227B-5 O-ring in the bottom of the cup,
care shall be taken to obtain samples having identical analyses.
and with the brass O-ring seating tool force it down until it is
Particular care shall be taken to keep the samples dry, as
firmly seated.
moisture may have an adverse effect.
7.1.4 Fill the syringe with liquid and sweep out all en-
trapped air; wipe the point of the needle free of liquid; lower
7. Procedure
the point to the bottom of the cavity; carefully inject 0.03 mL
7.1 Results of this test have been found to be temperature-
into the cavity.
dependent. It is therefore very important to provide means to
7.1.5 Slide a diaphragm across the top surface of the cup so
thermostat the sample cups, pistons, body of the assembly, and
that it drops flat onto the O-ring.
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