ASTM D2539-93

Standard Test Method for Shock Sensitivity of Liquid Monopropellants by the Card-Gap Test

SCOPE
1.1 In considering the handling properties of a liquid propellant, serious consideration is given to the possibility of hazard initiated by hydrodynamic shock. The consequences of such a shock may include: (1) nonpropagating explosion, (2) propagating but low-velocity detonation, and (3) propagating high-velocity detonation. All three are hazards; the test described herein is useful for one hazard only, namely propagating high-velocity detonation.
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.

General Information

• Status: Historical
• Publication Date: 14-Mar-1993
• Technical Committee: F07 - Aerospace and Aircraft

Relations

• Replaced By: ASTM D2539-93(2001) - Standard Test Method for Shock Sensitivity of Liquid Monopropellants by the Card-Gap Test (Withdrawn 2003)
• Effective Date: 15-Mar-1993

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 2539 – 93 An American National Standard
Standard Test Method for
Shock Sensitivity of Liquid Monopropellants by the Card-
Gap Test
This standard is issued under the fixed designation D 2539; 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 liquid) can be needed to define its sensitivity value. Because of
the destructive nature of the test, a sufficient supply of
1.1 In considering the handling properties of a liquid pro-
expendable parts must be available before a sensitivity deter-
pellant, serious consideration is given to the possibility of
mination is attempted.
hazard initiated by hydrodynamic shock. The consequences of
2.2 The card-gap test described is a measure of the hydro-
such a shock may include: (1) nonpropagating explosion, (2)
dynamic shock required to produce a stable, high-velocity
propagating but low-velocity detonation, and (3) propagating
detonation in a 1-in. standard steel pipe. Because of the large
high-velocity detonation. All three are hazards; the test de-
sample size subjected to this detonability test, the test is not to
scribed herein is useful for one hazard only, namely propagat-
be done in the laboratory. The advantages of the card-gap test
ing high-velocity detonation.
are its practical scale, reproducibility, and moderate material
1.2 This standard should be used to measure and describe
cost. The interpretation of results of the test is a matter of
the properties of materials, products, or assemblies in response
considerable judgment. While a propellant may show a low
to heat and flame under controlled laboratory conditions and
sensitivity in the card-gap test, this does not preclude the
should not be used to describe or appraise the fire hazard or
possibility of other dangers. On the other hand, a very high
fire risk of materials, products, or assemblies under actual fire
card-gap sensitivity does not always preclude the usability of
conditions. However, results of this test may be used as
such a liquid propellant, since it is possible that suitable
elements of a fire risk assessment which takes into account all
engineering design can incorporate preventative measures
of the factors which are pertinent to an assessment of the fire
against propagation of detonation. It is known that the degree
hazard of a particular end use.
of confinement, size, and material of the container, among
1.3 This standard does not purport to address all of the
other parameters, influence detonation propagation; therefore,
safety problems, if any, associated with its use. It is the
the results of any specific test may be highly apparatus-
responsibility of the user of this standard to establish appro-
dependent.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
NOTE 1—Gap tests for determining explosive sensitivity are new. A
1.4 The values stated in SI units are to be regarded as the
technique of using paper cards for the gap materials and steep pipe for
containers was developed in England at the Explosives Research and
standard. The values given in parentheses are for information
Development Establishment. The version described herein is essentially
only.
the Naval Ordnance Laboratory modification. The test is valuable because
it yields reproducible data and it has been found that results of different
2. Summary of Test Method
investigators show close agreement.
2.1 This test method gives an evaluation of the sensitivity of
a high-energy liquid propellant in terms of a stack of plastic
3. Significance and Use
cards inserted between a sample of liquid and a standard
3.1 The property measured is the tendency of a propellant to
booster charge of high explosive. The sensitivity value is taken
undergo a high-order detonation when subjected to a given
as the number of cards required to attenuate the booster shock
hydrodynamic shock. One limitation of the test is the difficulty
just enough that the liquid detonates in 50 % of the trials. For
of applying it to materials under conditions where the vapor
an unknown liquid, 15 to 25 shots (requiring up to 1000 mL of
pressure exceeds 1 atm.
3.2 The test is valuable because it yields very reproducible
1 data, and it has been found that results of different investigators
This test method is under the jurisdiction of ASTM Committee F-7 on
Aerospace Industry Methods and is the direct responsibility of Subcommittee show close agreement.
F07.02 on Propellant Technology.
Current edition approved March 15, 1993. Published May 1993. Originally
4. Apparatus
published as D 2539 – 66 T. Last previous edition D 2539 – 70 (1980).
4.1 Cup—The liquid under test is held in a cylindrical steel
This test method is identical in substance with the Card Gap Test for Shock
Sensitivity of Liquid Monopropellants recommended by the Interagency Chemical cup, closed at the bottom by a thin, flat diaphragm. It shall be
Rocket Propulsion Group, and published by the Chemical Propulsion Information
fabricated as follows (Fig. 1):
Agency, Test No. 1, March 1960.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2539
TABLE 1 Typical Experimental Data From a Sensitivity
from the furnace and cooled to room temperature, the tape is
Evaluation
ready for use.
Shot No. of Shot No. of
A A 4.1.5 The diaphragm shall be fused to the PTFE coating on
Result Result
No. Cards No. Cards
the pipe as follows: a piece of annealed tape shall be supported
1 0+14 20−
on a cushion of six layers of glass cloth stacked on a solid
2 32−15 19+
backing. The coated pipe shall be set on top of the tape,
3 16+16 20−
4 24−17 19+ weighted with 60 lb (27 kg), and heated for 15 min at 380°C.
5 20+18 20+
The weight shall be kept in place during the 15-min cooling
6 22−19 21−
period. Excess tape shall be trimmed off.
7 21−20 20−
8 20−21 19−
4.1.6 The finished cup shall be tested for leaks before use.
9 19+22 18+
4.1.7 Alternatively, the diaphragm can be formed from
10 20+23 19+
0.002-in. (0.05-mm) polyethylene film secured by a rubber
11 21+24 20+
12 22−25 21−
band or the cardboard spacer. The film shall be stretched taut
13 21 −
and is perfectly acceptable as long as it does not leak or react
A
Key: + 5 liquid detonated.
with the liquid to be contained.
− 5 liquid failed to detonate.
4.2 Booster—The booster charge shall consist of a cylindri-
cal tetryl pellet (Note 2) nominally 1 in. (25.4 mm) high by 1 ⁄8
TABLE 2 Data of Table 1, Arranged to Show 50 % Point
in. (41.3 mm) in diameter, weighing about 50 g. The density of
No. of Cards Result 3
these pellets should be 1.57 6 0.03 g/cm in accordance with
0+
Army ordnance Drawing 82-3-591C.
16 +
18 +
NOTE 2—Pentolite may not be substituted.
19 ++++−
NOTE 3—Warning: Tetryl is a highly toxic material; those who handle
20 ++++−−−−
it should exercise particular care to avoid spreading the dust by contact of
21 −−−−+
the hands with other parts of the body. Frequent washing of the hands with
22 −−
soap and water is desirable. Working garments should be free from
24 −
32 − dust-collecting features such as trouser cuffs, and should be laundered
frequently. Although not regarded as unusually sensitive, tetryl is a very
powerful explosive and shall be handled with due respect. Rough or
careless treatment of any sort shall be entirely avoided.
4.1.1 Each end of a section of 1-in. Schedule 40 extruded
4.3 Cards —The variable gap shall be built from circular
black steel pipe shall be faced in a lathe to produce an overall
cards, 1.55 in. (39.4 mm) in diameter, punched from cellulose
length of 3.0 in. (76.2 mm).
acetate sheet nominally 0.010 in. (0.254 mm) thick. The sheet
4.1.2 The pipe shall be degreased in a solvent bath. The
stock shall have smooth surfaces free from ripples, thick spots,
inside must be very smooth, clean, and free from pitting and
and dimples, and should be dimensionally stable; thickness
rust to facilitate coating. Superficial rust can be removed by
shall be held to close tolerances. Because of its thermoplastic
burnishing with a suitable wire brush.
nature, acetate sheet is not suitable as a gap material where
4.1.3 The pipe shall be dipped into a bath of undiluted sensitivity determinations are being carried out at temperatures
polytetrafluoroethylene (PTFE) black enamel and set upright much in excess of 100°C. In the event that such investigations
on blotting paper for a draining period of at least 10 min. After are undertaken, it will be necessary to find a gap material
dimensionally stable at high temperature.
drying in an oven at 90°C for 10 min, it shall be baked at 380°C
for 15 min. The enamel coating produced in this manner 4.4 Target Plate—Following a test shot, evidence is re-
quired to show whether or not the liquid has detonated. This
provides sufficient protection from liquids as corrosive as 90 %
nitric acid (HNO ) at room temperature. For further protection, evidence is provided by the condition of the target plate, a
cold-rolled mild steep plate 4 by 4 by ⁄8 in. (102 by 102 by 9.5
the pipe can be given supplemental coats of PTFE aqueous
dispersion. These shall be applied in exactly the same manner mm), which shall be placed in a horizontal position directly
above the cup. It shall rest on a cardboard collar which fits
as that used for the original coat of black enamel. Each coat can
be dried and fused before applying the next one. tightly around the outside of the cup and supports the plate at
1 1
a distance of ⁄8 to ⁄4 in. (3.2 to 6.4 mm) above the surface of
4.1.4 The diaphragm shall be made from 0.003-in. (0.08-
the liquid. A gap is recommended to prevent chemical reaction
mm) PTFE tape. As received from the manufacturer, the tape is
between corrosive liquids and the target plate, and to prevent
not suitable for use, since there are unrelieved stresses present
heat transfer between plate and liquid in tests above or below
which produce wrinkling in the finished diaphragm. To correct
ambient temperature.
this condition, the material shall be annealed as follows: the
4.5 Detonator Support Block—The tetryl booster pellet
tape shall be cut into 1 ⁄4-in. (44.5-mm) lengths which are
shall rest on a cylindrical block, 1.57 in. (39.9 mm) in diameter
placed between two pieces of glass-cloth tape. One layer of
and 1 in. (25 mm) high, aligned axially with the pellet. The
these sandwiches shall be placed on a smooth sheet of stainless
block shall be made from cork or soft wood, with a 0.280-in.
steel and covered with a flat piece of asbestos paper ⁄16-in. (1.6
mm) thick. The entire assembly shall be baked in a furnace at
380°C for 30 to 40 min, after which time the oven shall be
turned off and allowed to cool for 1 to 2 h. After it is removed Eastman Kodak Co.’s Kodapak IV has been found satisfactory for this purpose.
D 2539
TABLE 3 Abbreviated Procedure for Determination of 50 % Point for Various Materials With a Sharp Cutoff(After
A
Detonation on First Test at Zero Gap)
B B
Basic Test Pattern Results of Supplementary Tests
Supplementary Tests Required
Number of Cards Number of Cards
Designation to Establish 50 % Point 50 % Point
NN+1 N−1 N+2
I ++ −− none . . N + ⁄2
II +− −+ none . . N + ⁄2
III +− −− two tests at N−1 −− . N−1
++ . N
−+ . N − ⁄2
IV ++ −+ two tests at N + 2 . −− N+1
... ++ N+2
... −+ N+1 ⁄2
A
Key: N 5 an integer
+ 5 detonation
− 5 no detonation
... 5 no tests needed
B
For a particular number of cards the order in which the results are obtained is immaterial.
TABLE 4 Sample Determination of 50 % Point Using
consists of a series of nested cardboard support tubes on a steel
Abbreviated Procedure
firing pedestal, as shown in Fig. 2. Snugness of fit of the tubes
No. of Symbol
is critical. A set known as a NOLGAP assembly consists of one
Step Result of Test
Cards in Table 1
support tube, one pellet tube, one coupling tube, and two collar
50 % Point 5 10 Cards
tubes. The firing pedestal supports the entire test assembly at a
1 0 . +
convenient working height. Complete details of its construc-
2 8 . +
tion are given in Fig. 3. An alternative charge assembly design
3 16 . −
4 12 . − developed by Army Ballistic Missile Agency is shown in Figs.
4 and 5.
510 N +
611 N + 1 − basic test configura- 4.8 Firing Chamber—It is necessary to provide protection
710 N − % tion
from high-velocity shrapnel and some means of recovering the
811 N+1 −
target. In some instances it is also desirable to reduce noise
99 N − 1 +supplementary test from the shot. One solution consists in using an all steel
10 9 N−1 +
chamber in the shape of a simple maze (Fig. 6). Less elaborate
50 % Point 5 11.5 Cards
structures have been developed at other laboratories and
1 0 . + function satisfactorily.
2 8 . +
4.8.1 Another chamber is illustrated in Fig. 7. The rein-
3 16 . −
forced concrete wall is employed to protect personnel who
412 N + 2 −supplementary test
conduct the test from a distance of 200 ft (61 m). This type of
510 N +
enclosure is only acceptable where three sides of the test site
611 N + 1 − basic test configura-
710 N + tion are unoccupied for a distance of several hundred feet, since it
811 N+1 +
is possible that some shrapnel may travel this distance. It is
recommended that the side apron of the metal shield be lined
912 N + 2 +supplementary test
with a layer of high-strength steel since this area sustains the
most severe damage. Additional liners can be welded on at the
(7.11-mm) hole along its cylindrical axis. This hole shall be of
site as needed. Fig. 8 illustrates another possible test shelter.
such diameter that the detonator will slide into it with a snug
4.9 Firing Equipment—Before each shot, the firing circuit
push-fit. The block itself shall rest on the shoulder formed at
should be tested for continuity with a blasting galvanometer.
the junction of the pellet tube and support tube.
The shot may conveniently be fired from the remote control
4.6 Detonator—Detonation in the booster pellet shall be
point by means of a portable “blasting machine.” The firing
initiated by an electric blasting cap which fits snugly into the
line should consist of 16-gage or heavier duplex copper
hole drilled through the detonator support block, its tip just
conductor cable.
touching the center of the bottom face of the pellet. The cap
used is known as the Engineer Corps Special, and is consid-
5. Hazards
erably more powerful than the No. 8 commercial cap.
5.1 Because of the fairly large quantities of explosives
NOTE
...