Exudation test for blasting explosives of Type A
Blasting explosives of type A (UN No. 0081) shall, if they contain more than 40% liquid nitric ester, in addition to the testing specified in the Manual of Tests and Criteria, satisfy the following exudation test.
The apparatus for testing blasting explosive for exudation (figs. 1 to 3) consists of a hollow bronze cylinder. This cylinder, which is closed at one end by a plate of the same metal, has an internal diameter of 15.7 mm and a depth of 40 mm. It is pierced by 20 holes 0.5 mm in diameter (four sets of five holes) on the circumference. A bronze piston, cylindrically fashioned over a length of 48 mm and having a total length of 52 mm, slides into the vertically placed cylinder. The piston, whose diameter is 15.6 mm, is loaded with a mass of 2 220 g so that a pressure of 120 kPa (1.20 bar) is exerted on the base of the cylinder.
A small plug of blasting explosive weighing 5 to 8 g, 30 mm long and 15 mm in diameter, is wrapped in very fine gauze and placed in the cylinder; the piston and its loading mass are then placed on it so that the blasting explosive is subjected to a pressure of 120 kPa (1.20 bar). The time taken for the appearance of the first signs of oily droplets (nitroglycerine) at the outer orifices of the cylinder holes is noted.
The blasting explosive is considered satisfactory if the time elapsing before the appearance of the liquid exudations is more than five minutes, the test having been carried out at a temperature of 15 °C to 25 °C.
Test of blasting explosive for exudation
Tests relating to nitrated cellulose mixtures of Class 4.1
Nitrocellulose heated for half an hour at 132 °C shall not give off visible yellowish-brown nitrous fumes (nitrous gases). The ignition temperature shall be above 180 °C. See 2.3.2.3 to 2.3.2.8, 2.3.2.9 (a) and 2.3.2.10 below.
3 g of plasticized nitrocellulose, heated for one hour at 132 °C, shall not give off visible yellowish-brown nitrous fumes (nitrous gases). The ignition temperature shall be above 170 °C. See 2.3.2.3 to 2.3.2.8, 2.3.2.9 (b) and 2.3.2.10 below.
The test procedures set out below are to be applied when differences of opinion arise as to the acceptability of substances for carriage by road.
If other methods or test procedures are used to verify the conditions of stability prescribed above in this section, those methods shall lead to the same findings as could be reached by the methods specified below.
In carrying out the stability tests by heating described below, the temperature of the oven containing the sample under test shall not deviate by more than 2 °C from the prescribed temperature; the prescribed duration of a 30-minute or 60-minute test shall be observed to within two minutes. The oven shall be such that the required temperature is restored not more than five minutes after insertion of the sample.
Before undergoing the tests in 2.3.2.9 and 2.3.2.10, the samples shall be dried for not less than 15 hours at the ambient temperature in a vacuum desiccator containing fused and granulated calcium chloride, the sample substance being spread in a thin layer; for this purpose, substances which are neither in
powder form nor fibrous shall be ground, or grated, or cut into small pieces. The pressure in the desiccator shall be brought below 6.5 kPa (0.065 bar).
Before being dried as prescribed in 2.3.2.6 above, substances conforming to 2.3.2.2 shall undergo preliminary drying in a well-ventilated oven, with its temperature set at 70 °C, until the loss of mass per quarter-hour is less than 0.3% of the original mass.
Weakly nitrated nitrocellulose conforming to 2.3.2.1 shall first undergo preliminary drying as prescribed in 2.3.2.7 above; drying shall then be completed by keeping the nitrocellulose for at least 15 hours over concentrated sulphuric acid in a desiccator.
Test of chemical stability under heat
(a) Test of the substance listed in paragraph 2.3.2.1 above.
(i) In each of two glass test tubes having the following dimensions:
length 350 mm
internal diameter 16 mm
thickness of wall 1.5 mm
is placed 1 g of substance dried over calcium chloride (if necessary the drying shall be
carried out after reducing the substance to pieces weighing not more than 0.05 g each).
Both test tubes, completely covered with loose-fitting closures, are then so placed in an
oven that at least four-fifths of their length is visible, and are kept at a constant
temperature of 132 °C for 30 minutes. It is observed whether nitrous gases in the form of
yellowish-brown fumes clearly visible against a white background are given off during
this time;
(ii) In the absence of such fumes the substance is deemed to be stable;
(b) Test of plasticized nitrocellulose (see 2.3.2.2)
(i) 3 g of plasticized nitrocellulose are placed in glass test tubes, similar to those referred to
in (a), which are then placed in an oven kept at a constant temperature of 132 °C;
(ii) The test tubes containing the plasticized nitrocellulose are kept in the oven for one hour.
During this time no yellowish-brown nitrous fumes (nitrous gases) shall be visible.
Observation and appraisal as in (a).