determinations are made initially, and the average is accepted if the average deviation of the mean (A. D.) is less than plus or minus 1.25 percent. Otherwise, further determinations will be made until the above criterion is satisfied or until a total of six determinations has been obtained.8*+ 16.22 Application of tolerances. The tolerances applied, using the rules in this part, are: Rate of detonation (the average of 3 to 6 determinations with Mettegang recorder): Plus or minus 15 percent. Unit deflective charge determined by the ballistic pendulum as compared with the Pittsburgh testing station standard 40-percent straight nitroglycerin dynamite (the average of 3 to 6 determinations with the ballistic pendulum): Plus or minus 10 percent. Grams of wrapper per 100 grams of explosive: Plus or minus 2 grams (average of four determinations): Provided, That the manufacturers shall submit samples of all different sizes of cartridges, to be considered as part of the original sample, the amount of wrapper to be determined for each size of sample; and, Provided further, That the tolerances as suggested shall be determined in comparison with various diameters of samples as submitted with the original sample. Apparent specific gravity of cartridge, by sand: Plus or minus 7.5 percent (average of four determinations): Provided, That actual density shall be determined on cartridges of the same diameter as the standard; and, Provided further, That manufacturers shall be required to submit samples of all sizes. Gallery No. 1: No ignition must be obtained in each of one or more trials. NOTE: In the retesting of permissible explosives by tests 1 and 4, the charges of the explosives fired will be reduced 10 percent in weight from the weights originally used in order to eliminate any likelihood of a failure being due to the natural variations in the gallery conditions. ** 16.23 Pendulum friction test. Each explosive must pass a test of 10 trials under the same conditions as originally tested, except the height of fall of the hard-fiber-faced shoe will be reduced by 10 percent in order to eliminate any likelihood of a failure being due to the natural variations in test conditions.*† 16.24 Field samples of permissible explosives. The Bureau will from time to time reexamine permissible explosives found in commercial shipments and in the field in order to determine how closely they conform to the samples upon which the permissibility tests were originally made, and the manufacturer will be notified of the results of tests of all field samples. In order that this examina 8 In the case of a doubtful result, the mean and average deviation from the mean (A. D.), omitting the doubtful observation, are found; then the difference between the doubtful observation and the mean is determined, and if this is equal to or greater than 4 A. D., it is rejected, and the remaining results are averaged. Page 88 **For statutory and source citations, see note to § 16.0. tion can be properly made, the tolerances as given above are applied in the manner stated below, according to the rules and regulations promulgated November 15, 1920, and February 26, 1921. These methods of applying the tolerances supersede all previous methods. In the event that a field sample of a permissible explosive exceeds the tolerance of one or more items, the Bureau will take the following action: (a) If the explosive exceeds the tolerance for any items of the chemical analysis, for grams of wrapper per 100 grams of explosive, for apparent specific gravity, for rate of detonation, or for unit deflective charge, the manufacturer only will be advised of the results, except that, should these results, in the opinion of the explosives engineer, indicate that the explosive is unsafe for use, then the operator or owner will be immediately warned and further tests promptly inaugurated. (b) If the explosive exceeds the tolerance for gallery tests, pendulum-friction test, or poisonous gases, the Bureau will declare that particular lot of explosives not permissible, and a copy of the notification to the consumer or owner will be furnished the manufacturer, the notification to state that the explosive did not meet requirement tests. The term "Lot of permissible explosives" as used in the tolerances promulgated by the Director is defined as "all of that explosive in the magazine from which the sample is procured, bearing identical case markings." When a given lot of explosive is declared not permissible and the owner and the manufacturer are notified, the Bureau does not attempt to fix responsibilities between owner and manufacturer. The usual causes of an explosive exceeding the tolerances for chemical analysis or physical tests are: (c) It may not have been properly manufactured. (d) It may not have been properly stored. The manufacturer is responsible for paragraph (c) because the consumer has no control over the method of manufacture of the explosive, but the consumer or owner is responsible for paragraph (d) because the manufacturer has no control over the conditions of storage when the explosive has once passed from his ownership. The manufacturer should exercise due care that the quality of the raw materials, as well as the weighing and incorporating of them, is similar in all respects to that for the original sample of explosives submitted for tests; and that the explosive is fresh and in first-class condition when sold. The user should store explosives in wellventilated magazines, at temperatures not exceeding 90° F. The boxes should be placed so that the cartridges lie horizontally, though the tops of the boxes may be up or down. The explosives purchased first should be used first, and hence older explosives should not be stored under or behind a fresh consignment. It is well to purchase explosives in such quantities that they can be used promptly.*† **For statutory and source citations, see note to § 16.0. Page 89 Sec. PART 17-BLASTING DEVICES Sec. 17.0 Compliance with the require- 17.9 Test requirements of blasting devices for admittance to permissible list. ments necessary for obtaining 17.1 Definition of a permissible blast. 17.2 Fees. 17.3 Form for making applications. 17.4 Instructions on submitting equipment. 17.5 Conditions under which blasting devices will be tested. 17.6 Prescribed conditions for use of blasting devices. 17.7 Conditions under which a permissible blasting device should not be used. 17.8 Complete official test. 17.10 Poisonous gases. 17.13 Gallery tests. 17.17 How approvals are granted. 17.19 Withdrawal of approval. CROSS REFERENCE Regulations of the Geological Survey relating to the storage, transportation, and use of explosives: See §§ 211.79-211.91. Section 17.0 Compliance with the requirements necessary for obtaining approval. To receive approval of the Bureau of Mines for any blasting devices a manufacturer must comply with the requirements specified in this part.*t *§§ 17.0 to 17.21, inclusive, issued under the authority contained in sec. 5, 37 Stat. 682, sec. 311, 47 Stat. 410; 30 U.S.C. 7; E.O. 4239, June 4, 1925. †The source of 88 17.0 to 17.21, inclusive, is Schedule 20, Secretary of Commerce, Sept. 19, 1928. 17.1 Definition of a permissible blasting device. The term "blasting device" includes all devices designed for breaking down coal except (a) devices, such as wedges, hydraulic devices, and the like, whose operation is wholly mechanical, and which, obviously, present no hazard of ignition of gas or dust in coal mines; and (b) explosives of the permissible type which are tested under Part 16. A permissible blasting device is a device for breaking down coal which is similar in all respects to the sample of this device which passed the tests prescribed by the Bureau of Mines to determine its safety for use in coal mines. A permissible blasting device is permissible only when it is used in accordance with the conditions prescribed by the Bureau of Mines.** CROSS REFERENCE: For regulations prescribing conditions for approval of the Bureau of Mines of blasting devices and explosives, see Part 15. 17.2 Fees. Complete tests of blasting devices will be carried out at the estimated costs which will be furnished by the Director, Bureau of Mines, Washington, D. C., after a consideration of the nature of the device and the tests to be carried out. Tests to assist a manufacturer in the development of his device may be made upon request to Page 90 **For statutory and source citations, see note to § 17.0. the Director of the Bureau and will be charged for in amounts proportionate to the work involved.*+ 17.3 Form for making applications. A form of request for an investigation of a blasting device follows: THE DIRECTOR OF THE BUREAU OF MINES, DEPARTMENT OF THE INTERIOR, Washington, D. O. DEAR SIR: We hereby make application for permissibility tests of the_------blasting device. A copy of this application, two sets of drawings, one uncharged assembled apparatus, and a full set of instructions for operating are being sent to the Pittsburgh Experiment Station, 4800 Forbes St., Pittsburgh, Pa., marked for the "Attention of the Explosives Engineer." 17.4 Instructions on submitting equipment. (a) One complete device, with two sets of assembly and detail drawings that show the construction of the device and the materials of which it is made, should be forwarded to the Pittsburgh Experiment Station at the time application for tests is made. (b) When this has been inspected by the Bureau's engineers, the applicant will be notified of the amount of fees to be deposited and the quantity of material that will be required for the tests. The applicant will be notified of the date on which the tests will be started and will be given an opportunity to witness the tests.** 17.5 Conditions under which blasting devices will be tested. The conditions under which the Bureau of Mines will test blasting devices under this part are as follows: (a) Applications for tests shall be addressed to the Director, Bureau of Mines, Washington, D. C. (b) Tests will be made at the Explosives Experiment Station of the Bureau of Mines at Bruceton, Pa. (c) The manufacturer or applicant desiring tests to be made shall ship and install at the Explosives Experiment Station, Bureau of Mines, Bruceton, Pa., such equipment and material as may be necessary for carrying out the tests, and furnish the necessary labor for operation of the equipment. (d) No one is to be present at or participate in these tests except the necessary Government officers at the experiment station, their assistants, and the representatives of the manufacturer of the device or the applicant desiring tests to be made. (e) The tests will be made in the order of the receipt of the applications for them, provided the necessary equipment has been received at the experiment station by the date set, of which due notice will be given by the Bureau of Mines. (f) A list of the devices that pass the requirements will be made public in such manner as may be considered desirable. (g) The results of tests are to be considered confidential within the applicant's organization and are not to be made public prior to official publication by the Bureau.** **For statutory and source citations, see note to § 17.0. Page 91 17.6 Prescribed conditions for use of blasting devices. (a) That the device is in all respects similar to the sample submitted by the manufacturer for tests. (b) That the maximum charge used for a blast shall not exceed the maximum charge tested and found to be safe under test conditions. (c) Other conditions which may be set down by the Bureau as appropriate to the particular device tested.** 17.7 Conditions under which a permissible blasting device should not be used. After a device has passed the required tests and its name has been published in a list of permissible blasting devices, it is not used in a permissible manner if one or more of the following conditions prevail: (a) If used in excess of the maximum permissible charge. (b) If fired without stemming, except when the device employed is self-stemming, or in case no heat is evolved in the process, or in any part of the process, sufficient to cause the ignition of methane or coal dust. (c) If fired with combustible stemming, except where no heat is evolved in the process, or in any part of the process, sufficient to cause the ignition of methane or coal dust. (d) If fired in the presence of a dangerous percentage of fire damp. (e) If fired under other specific prohibited conditions laid down after tests on a particular device. (f) If the device is charged or assembled at the mine, and if, in the opinion of the Bureau, the charging involves danger of igniting a gassy atmosphere or initiating a coal-dust explosion, such charging shall be carried out above ground and only the completely assembled device shall be taken into the mine.* 17.8 Complete official test. A complete official test of a blasting device for use in coal mines may involve the following: (a) Physical examination. The manufacturer shall submit with the device two complete sets of blue prints of the device and specifications for materials. (b) Analysis of any chemical material used as the blasting agent or for the initiation or advancement of the reaction taking place. (c) Propulsive strength. 8 (d) Gallery tests with a gas-air mixture containing 8 percent of natural gas and also with 4 percent of gas and coal dust on the side shelves. (e) Gaseous products from reaction. (f) In addition, such other tests as in the opinion of the Bureau's explosives engineers are considered advisable.* 17.9 Test requirements of blasting devices for admittance to permissible list. All devices submitted for admittance to the permissible list of blasting devices must pass any or all of the following physical tests, which may be required of the particular device, without showing any unfavorable results.*+ 17.10 Poisonous gases. The maximum permissible charge must evolve less than 53 liters of poisonous gases (CO, H2S, oxides of N.) ** Page 92 **For statutory and source citations, see note to § 17.0. |