Washington, DC: U.S. Department of the Interior, Bureau of Mines, Bulletin 78, 1920 Feb; :1-53
Approvals No. 104 and No. 104A were issued January 16, 1919. "When constructed in conformity with the machine tested and approved, the CE-7, a. c. equipments are considered safe units and are recommended for use in gaseous mines. In being accorded a place in the bureau's permissible list, the foregoing equipments all met the requirements of Schedule 2A: 1. In construction, they are considered rugged enough to stand reasonably severe service. The casings have adequate strength to withstand any internal explosion of fire damp. 2. In those machines having protective devices, these devices have proven under test to be "capable of preventing the passage of flames from the interior to the exterior of casings. The design of these devices and their location within the casings afford protection against mechanical injury while in place, and minimize the accumulation of coal dust in openings. 3. "Where flanged joints are used in explosion-proof casings these joints have been made wide enough to satisfy the test requirements with respect to the maximum indicated pressures during the explosion tests. 4. The construction of the machines was shown by test to prevent the development of dangerous afterburning. The bureau recommends all approved equipments for use in mines where fire damp may accumulate. The demand for such apparatus will depend mainly on the attitude that the mine owner or person in position to purchase mine equipment has toward safety apparatus. The more the doctrine of "safety first" is practised the greater will be the demand for reasonably safe equipment. Also, as the operator or responsible official comes more and more to recognize the need of such apparatus and to see in it a safety device he will feel a greater interest in it and will assist the bureau and the manufacturer in keeping it in a safe condition. During the war there was a tendency, under the stress of the demand for more and still more coal, to disregard safety and the demand for unapproved apparatus was noticeable. When conditions again become normal the bureau looks forward to new and greater interest in safety methods and in safety apparatus. The bureau has other applications on file and expects that several more coal-cutting equipments will be added to the present list within the next two years. With the list already approved from which to select, there would seem to be no reason why the operator who wants to safeguard his men can not find a unit that meets his requirements. The cooperative spirit shown by the various manufacturers whose machines are herein described has been greatly appreciated, and the continuation of such relations between the bureau and those who submit explosion-proof apparatus can but tend to render coal mining safer. Because both the "open" and permissible or explosion-proof types of coal-cutting machines are on the market the distinction between them may not always be evident from the designation given them by the manufacturer. Permissible equipments, however, can always be distinguished by the Department of the Interior, Bureau of Mines, approval plate, which the manufacturer is required to attach to each approved outfit.
Washington, DC: U.S. Department of the Interior, Bureau of Mines, Bulletin 78