(b) Bulb life. The average life of the bulbs shall be not less than 200 hours, and at least 92 percent of the bulbs shall have a life of 150 hours. The life of a bulb is the number of hours its main filament will burn in the cap lamp or its equivalent.

The life of a bulb having main filaments in parallel is considered ended when the first filament ceases to burn; the life of a bulb having independent main filaments is considered ended when the last filament ceases to burn.

(c) Bulb uniformity. (1) The bulbs submitted shall meet the following minimum requirements for variation in current consumption and candlepower:

(2) The current consumption of at least 94 percent of the bulbs shall not exceed the average current by more than 6 percent. The candlepower (s. cp.) of at least 90 percent of the bulbs shall not fall short of the average candlepower by more than 30 percent.

§ 19.10

Material required for Bureau of Mines records.

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

(a) Drawings. The original drawings submitted with the application for the tests and the final drawings, which the manufacturer must submit to the Bureau before the approval is granted, to show the details of the lamp as approved. These drawings are used to identify the lamp in the approval and as a means of checking the future commercial product of the manufacturer.

(b) Actual equipment. (1) If the Bureau so desires, parts of the lamps which are used in the tests will be retained as a permanent record of the investigation and of the lamps submitted.

(2) If the lamp is approved, the Bureau will require the manufacturer, as soon as his first manufactured lamps are available, to submit one complete lamp, bearing the approval plate, as a record of his commercial product.

§ 19.11

How approvals are granted.

(a) All approvals are granted by offcial letter from the Bureau of Mines. A lamp will be approved under this part only when the testing engineers judge that the lamp has met the requirements of the part and the Bureau's records concerning the lamp are complete, including drawings from the manufacturer that show the lamp as it is to be commercially made. No verbal reports of the Bureau's decisions concerning the investigation will be given, and no informal approvals will be granted.

(b) As soon as the manufacturer has received the formal approval he shall be free to advertise his lamps as permissible. [Sched. 6D, 4 F. R. 4003, Sept. 21, 1939, as amended by Supp. 1, 19 F. R. 2718, Apr. 23, 1955]

§ 19.12 Wording, purpose, and use of approval plate.

(a) Approval plate. The manufacturer shall attach, stamp, or mold an approval plate on the battery container of each permissible lamp. The plate shall bear the seal of the Bureau of Mines and be inscribed as follows: "Permissible Electric Cap Lamp. Approval No. issued to the

Company." When deemed necessary, an appropriate caution statement shall be added. The size and position of the approval plate shall be satisfactory to the Bureau.

The

(b) Purpose of approval plate. approval plate is a label which identifies the lamp so that anyone can tell at a glance whether or not the lamp is of the permissible type. By it, the manufacturer can point out that his lamp complies with specifications of the Bureau of Mines and that it has been judged as suitable for use in gassy mines.

(c) Use of approval plate. Permission to place the Bureau's approval plate on his lamp obligates the manufacturer to maintain the quality of his product and to see that each lamp is constructed according to the drawings which have been accepted by the Bureau for this lamp and which are in the Bureau's files. Lamps exhibiting changes in design which have not been approved are not permissible lamps and must not bear the Bureau's approval plate.

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

(a) The purpose of the investigations made under this part is to aid in the development and use of electric lamps, other than standard cap lamps, that may be used in mines, especially in mines that may contain dangerous proportions of methane.

(b) This part supersedes Schedule 10B, issued under date of June 1, 1932, and Schedule 11A, issued under date of January 13, 1936, and goes into effect May 17, 1938.

(c) Electric lamps and flashlights that meet the requirements set forth in this

(a) Adequate. Appropriate and sufficient as determined by mutual agreement between the manufacturer and the Bureau of Mines.

(b) Approval. Official notification in writing from the Bureau of Mines to a responsible organization, stating that upon investigation its lamp has been adjudged satisfactory under the requirements of this part.

(c) Explosion-proof compartment. An enclosure that withstands internal explosions of methane-air mixtures without damage to itself or discharge of flame and without ignition of surrounding explosive methane-air mixtures.

(d) Permissible. Completely assembled and conforming in every respect with the design formally approved by the Bureau of Mines under this part. (Approvals under this part are given only to equipment for use in gassy and dusty mines.)

[Sched. 10C, May 17, 1938, as amended by Supp. 1, 20 F. R. 2718, Apr. 23, 1955] § 20.3

Applications.

Before the Bureau of Mines will undertake the active investigation leading to approval of any lamp, the manufacturer shall make application by letter for an investigation of his lamp. This application in duplicate, accompanied by a check, bank draft, or money order, payable to the United States Bureau of Mines, to cover all the necessary fees, shall be sent to the Central Experiment Station, Bureau of Mines, 4800 Forbes Avenue, Pittsburgh, Pa., 15213, together with the required drawings, one complete lamp, and instructions for its operation.

[Supp. 1, 20 F. R. 2718, Apr. 23, 1955]

(i) Examining and recording drawings and specifications requisite to issuing an extension of approval -

(j) 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.

1 Applies to all lamps.

2 Applies only if cord is involved.

3 Applies only to storage-battery lamps. Applies only to trip lamps.

(a) One complete lamp, with assembly and detail drawings that show the construction of the lamp and the materials of which it is made, should be submitted at the time the application for investigation is made. This material should be sent prepaid to the Central Experiment Station, 4800 Forbes Avenue, Pittsburgh, Pa., 15213.

(b) When the lamp 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. He will also be notified of the date on which the tests will start and will be given an opportunity to witness the tests.

(c) 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.

(d) Permissibility tests will not be made unless the lamp is complete and in a form that can be marketed.

(e) 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 prior to the formal approval of the lamp by the Bureau of Mines.

(f) No verbal report of approval or disapproval will be made to the applicant. Approval will be made only in writing by the Bureau of Mines. The applicant shall not be free to advertise the lamp as being permissible, or as having passed the tests, prior to receipt of formal notice of approval.

[Sched. 10C, May 17, 1938, as amended by Supp. 1, 20 F. R. 2719, Apr. 23, 1955]

§ 20.6

General requirements.

(a) The lamps shall be durable in construction, practical in operation, and suitable for the service for which they are designed and approved.

(b) The intensity of light, distribution of light, and battery capacity shall be adequate for the use for which the lamp is intended.

(c) Battery terminals and leads therefrom, as well as the battery gas vents, shall be designed to minimize corrosion of the electrical contacts.

(d) Bulbs and other replacement parts of the lamps shall be adequately marked as a means of identification.

Two general classes of electric lamps are recognized in these requirements, namely: Class 1, those that are selfcontained and easily carried by hand, and class 2, those that may or may not be self-contained and not so readily portable as the first class.

(a) Class 1. Class 1 includes hand lamps, signal lamps, inspection lamps, flashlights, and animal lamps which are operated by small storage batteries or dry cells.

(b) Class 2. Class 2 includes lamps such as the pneumatic-electric types and large battery lamps.

(a) Protection against explosion hazards. Unless properly designed, class 1 lamps present two sources of probable explosion hazards: Ignition of an explosive atmosphere by the heated filament of the bulb in case the bulb glass is accidentally broken, and ignition by electric sparks or arcs from the battery or connections thereto. The Bureau, therefore, requires the following safeguards:

(1) Safety device. The lighting unit shall be provided with a safety device which shall prevent the ignition of explosive mixtures of methane and air by the heated filament if the bulb glass surrounding the filament is broken.

(2) Safety device (protection). The design of the safety device and the housing which protects it shall be such that the action of the safety device is positive; yet the lamp shall not be too readily extinguished during normal service by the unnecessary operation of the device.

(3) Locks or seals. For lamps other than flashlights, all parts, such as bulb housing and battery container, through which access may be had to live terminals or contacts shall be adequately sealed or equipped with magnetic or other equally reliable locks to prevent opening by unauthorized persons. flashlights, provision shall be made for sealing the battery container.

For

(4) Battery current restricted. Unless all current-carrying parts, including conductors, are adequately covered and protected by the sealed or locked compartments, the maximum possible current flow through that part shall be limited by battery design, or by an enclosedtype fuse inside the sealed or locked container, to values that will not produce

sparks or arcs sufficient to ignite an explosive mixture of methane and air.

(b) Protection against bodily hazard. This hazard is chiefly due to the possible burning of the user by electrolyte spilled from the battery. The Bureau, therefore, requires that:

(1) Spilling of electrolyte. The lamp shall be so designed and constructed that when properly filled the battery will neither leak nor spill electrolyte under conditions of normal use. Lamps passing a laboratory spilling test will be considered satisfactory in this respect, contingent upon satisfactory performance in service.

(2) Corrosion of battery container. The material of which the container is made shall resist corrosion under conditions of normal use.

§ 20.9 Class 2 lamps.

(a) Safety. (1) Unless special features of the lamp prevent ignition of explosive mixtures of methane and air by the broken bulb or other igniting sources within the lamp, the bulb and all sparkproducing parts must be enclosed in explosion-proof compartments.

(2) Explosion-proof compartments will be tested while filled and surrounded with explosive mixtures of Pittsburgh natural gas1 and air. A sufficient number of tests of each compartment will be made to prove that there is no danger of ignition of the mixture surrounding the lamp by explosions within the compartment. The lamp will not pass the above tests, even though the surrounding explosive mixtures are not ignited, if external flame is observed, if excessive pressures are developed, or if excessive distortion of any part of the compartment takes place.

(3) Glass-enclosed parts of such compartments must be guarded and be of extra-heavy glass to withstand pick blows, and be adequately protected by shrouds or by an automatic cut-out that opens the lamp circuit if the enclosure is broken.

(4) When an explosion-proof enclosure consists of two or more parts that are held together securely by bolts or some suitable means to permit assembly,

1 Investigation has shown that for practical purposes Pittsburgh natural gas (containing a high percentage of methane) is a satisfactory substitute for pure methane.