Pa., 15213, together with the required drawings, one complete blasting unit, and instructions for its operation. § 24.3

Conditions governing investiga

tions.

(a) One complete blasting unit, with drawings that show the construction of the device and the materials of which it is made, should be forwarded to the Central Experiment Station at the time the application for tests is made.

(b) When this has been inspected by the Bureau's engineers, the applicant will be notified as to the amount of material that will be required for the tests.

(c) 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.

(d) Observers at formal investigations and demonstrations. No one shall be present during any part of the formal investigation conducted by the Bureau which leads to approval for permissibility except the necessary Government personnel, representatives of the applicant, and such other persons as may be mutually agreed upon by the applicant and the Bureau. Upon granting approval for permissibility, the Bureau will announce that such approval has been granted to the device and may thereafter conduct, from time to time in its discretion, public demonstrations of the tests conducted on the approved device. Those who attend any part of the investigation, or any public demonstration, shall be present solely as observers; the conduct of the investigation and of any public demonstration shall be controlled wholly by the Bureau's personnel. Results of chemical analyses of material and all information contained in the drawings, specifications, and instructions shall be deemed confidential and their disclosure will be appropriately safeguarded by the Bureau.

(e) Permissibility tests will not be made unless the unit has been completely developed and is a form that can be marketed.

(f) The results of the tests shall be regarded as confidential by all present at the tests and shall not be made public in any way before the shot-firing unit is formally approved by the Bureau of Mines.

(g) No verbal report of approval or disapproval will be made to the applicant. After the Bureau's engineers have

considered the results of the tests, a formal report of the approval or disapproval will be made to the applicant in The writing by the Bureau of Mines. applicant shall not advertise the unit as being permissible or as having passed the tests before he receives formal notice of approval.

[Sched. 12D, 10 F. R. 14895, Dec. 11, 1945, as amended by Supp. 1, 20 F. R. 2719, Apr. 23, 1955]

§ 24.4 Requirements for approval.

Single-shot blasting units approved under this part shall be practical in construction and operation as well as suitable for service conditions underground. They shall offer no probable ignition hazard when used in gassy mine atmospheres. They shall meet, under laboratory test conditions, the following requirements of minimum performance:

(a) The unit shall fire consistently single electric blasting caps through a total resistance of 41⁄2 ohms.

(b) The unit shall not produce sparks capable of igniting explosive mixtures of methane and air.1

(c) Units of the battery type shall be designed to prevent accidental connection to the firing circuit. Batteries having a short-circuit current greater than 10 amperes, shall be enclosed in an effectively locked or sealed housing.

(d) Storage batteries supplying current for both blasting and illumination at the same time shall have ample capacity for the combined service or shall be equipped with an automatic device that cuts off the lamp during shot firing. The lamp part of the unit shall meet the requirements of the current lamp schedules.

(e) Magneto units shall be operable only by a special key or handle.

'Sparking tests of battery-type units will be made with a contactor disk 8 inches in condiameter equipped with brush-type tacts, each of approximately 50 No. 34 copper wires. The contactor will be surrounded by an explosive mixture of Pittsburgh natural gas and air. The test shall consist of making and breaking the discharge of each of three units at least 300 times with the contactor operating at 60 revolutions per minute. The resistance of the contactor circuit shall not be greater than 0.25 ohm. Similar tests will be made of magneto- and generator-type units but with the contactor equipped with a 16-inch bronze brush and brass contact and operating at speeds up to 1,200 revolutions per minute.

(f) A unit that depends on some special modification, such as a shunt resistance, to prevent igniting sparks, shall have its housing sealed or locked to prevent removal or disturbance of this safety feature.

[Sched. 12D, 10 F. R. 14895, Dec. 11, 1945, as amended by Supp. 1, 20 F. R. 2719, Apr. 23, 1955]

§ 24.5

Materials required for Bureau of Mines records.

In order that the Bureau may know exactly what it has tested and approved, it keeps detailed records covering each investigation. These records include drawings and actual equipment, as follows:

(a) Drawings. The original drawings submitted with the application for approval and any drawings that are needed to show changes in design. These drawings are used to identify the unit in the approval and to check the future product of the manufacturer.

(b) Actual equipment. If the Bureau so desires, parts of the units that are used in the tests will be retained as records of the equipment submitted. If the unit is approved, the Bureau will require the manufacturer to submit one of his units, with the approval plate attached, as a record of his future commercial product.

§ 24.6 Approvals.

All approvals are granted by letter from the Bureau of Mines. A blasting unit will be approved under this part only when the testing engineers shall have judged that it has met the requirements of the schedule and the Bureau's records are complete, including drawings from the manufacturer that show the unit as it is to be made. No verbal reports of the investigation will be given, and no informal approval will be granted. The manufacturer shall not advertise his blasting unit as permissible or approved until he has received the formal notification of approval from the Bureau of Mines.

[Sched. 12D, 10 F. R. 14895, Dec. 11, 1945, as amended by Supp. 1, 20 F. R. 2719, Apr. 23, 1955]

When deemed necessary, an appropriate cautionary statement shall be added. A photograph of the approval plate design will be supplied to the manufacturer with the approval letter. The size and position of the approval plate adopted shall be satisfactory to the Bureau.

(b) Purpose. The approval plate is a label that identifies the device so that any one can tell at a glance whether or not it is of the permissible type. By the plate, the manufacturer can point out that his blasting unit complies with the Bureau's requirements, and that it has been approved for use in gassy mines.

(c) Significance. Permission to place the approval plate on his unit obligates the manufacturer to maintain the quality of his product and to see that each unit is constructed according to the drawings that have been accepted and placed on file by the Bureau. Blasting units exhibiting changes in design that have not been authorized by the Bureau are not permissible and must not bear the approval plate.

§ 24.8 Withdrawal of approval.

The Bureau of Mines reserves the right to rescind for cause, at any time, any approval granted under this part.

§ 24.9 Future changes in design.

All approvals are granted with the understanding that the manufacturer will make each blasting unit according to the drawings that were submitted to the Bureau and that have been included in the approval. Changes in the design shall not be made without first obtaining the Bureau's authorization, procedure for which is as follows:

cations and requirements in this part and authorizing the use and attachment of an official approval plate.

(c) "Blasting unit" means an apparatus for detonating high explosives by applying electric current to electric detonators.

(d) "Multiple-shot blasting unit" means a blasting unit capable of detonating short-delay electric detonators, as further defined in § 25.20 or § 25.25.

(e) "Short-delay electric detonator" means a delay-type detonator (blasting cap) the delay periods of which range in nominal value from 25 to 500 milliseconds, and which will initiate (detonate) multiple charges of high explosives in succession with one application of the firing current.

(f) "Bureau" means the United States Bureau of Mines.

(g) "Applicant" means an individual, partnership, company, corporation, association, or other organization that designs, manufactures, or assembles, and that seeks a certificate of approval or preliminary testing of a multiple-shot blasting unit.

66-067 0-67-10

(1) Tests to assist an applicant in evaluating equipment intended for certification may be made at the discretion of the Bureau. Written requests for such tests shall be directed to the Chief, Branch of Electrical-Mechanical Testing. A deposit of $200 shall be paid in advance when such tests have been authorized. The fees charged shall be in amounts proportionate to the work performed based on normal charges. Any surplus will be refunded at the completion of the work, or applied to future work, as directed by the applicant.

[Sched. 16E, 30 F.R. 3756, Mar. 23, 1965]

§ 25.5 Tests and investigations.

Unless the application states otherwise, it will be presumed that a complete investigation for certification is desired. However, the application may be expressly limited to some element or phase less than a complete investigation; and in any case if the tests at any stage indicate that the unit does not conform to the specification in this part, the Bureau may treat the application as one for a partial investigation up to that point. Complete investigation for certification will not be undertaken unless the unit has been fully developed, is ready to be marketed, and is submitted completely assembled. The minimum material required for tests will be four complete units and such additional expendable parts as the Bureau may require.

§ 25.6 Applications.

(a) No investigation or testing will be undertaken by the Bureau except pursuant to a written application, in duplicate, accompanied by a check, bank draft, or money order, payable to the United States Bureau of Mines, to cover the fees, and all prescribed drawings, specifications, and related material. The application and all related matters and all correspondence concerning it shall be sent to the Central Experiment Station, Bureau of Mines, 4800 Forbes Avenue, Pittsburgh, Pennsylvania, 15213, Attention: Chief, Branch of Electrical-Mechanical Testing.

(b) The unit to be tested may be shipped (charges prepaid) at the same time the application is submitted, or at the option of the applicant shipment of the unit may be deferred until the

Bureau has notified the applicant that the application will be accepted.

(c) Drawings and specifications shall be adequate in number and detail to identify fully the design of the unit and to disclose its materials, detailed dimensions of all parts, and wiring diagram. Drawings must be numbered and dated to insure accurate identification and reference to records, and must show the latest revision. Specifications must be given for materials, components, and subassemblies.

§ 25.7

Specifications; all types of units. (a) The Bureau will not test or investigate any unit that in its opinion is not constructed of suitable materials, that evidences faulty workmanship, or that is not designed upon sound engineering principles. In addition to any specifications or requirements imposed by the regulations in this part, the Bureau may impose such further specifications or requirements as in its opinion are necessary or proper to investigate or test the particular device submitted.

(b) Any unit that satisfies all of the requirements of this part may be certified as permissible.

(c) Adequacy of design and construction will be determined in connection with the following factors: Kind and durability of materials, test of active parts, resistance to moisture, drop test, insulation measurements, durability of construction, practicality in operation, suitability for underground service, and performance characteristics during the investigation.

(d) The unit shall not ignite explosive gas-air mixtures or cause misfires or premature firing when operated according to the applicant's prescribed conditions of use, which shall be acceptable to the Bureau.

(e) The firing operation must be accomplished by a removable key or other acceptable means to prevent accidental or premature firing.

(f) A suitable means, incorporated as an integral part of the blasting unit, shall be provided to indicate, before each round of shots is fired, that the voltage applied to the firing line is adequate to meet the requirements as stated in paragraphs (h) and (i) of this section. An automatic means to prevent inadvertent or deliberate firing prior to the indication of readiness shall be incorporated in the unit.