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Wilcox insulating firebrick having a low heat-storage capacity, assure a uniform distribution of heat over the entire drum, The proposed boiler rules state that the drum shall be heated uni- formly to at least 1100 degrees Fahr., and that the drum shall be brought slowly up to the specified tempera- ture and held at that temperature for a period of at least one hour per inch of thickness, and then allowed to cool slowly in a still atmosphere. The total time required for the stress- relieving operation thus depends largely upon the thickness of the drum plate, but a drum of average size can be stress-relieved in 6 to 8 hours. Following the stress-relieving of completed drums, they are subjected to the hydrostatic test required by the rules to which they have been fabricated. The proposed rules for marine service require a test pres- sure of one and one-half times the working pressure, Test Plates Defined The proposed rules also specify that, during the welding process, test plates, secured to the end of the drum at the longitudinal seam, are to be welded together in the same manner as the longitudinal seam, This, of course, is standard practice and has been followed for some time in order to provide means for deter- mining the physical properties of the weld-metal and the welded joint, The test piece is not removed from the drum until after the stress-relieving operation is completed. It is then taken off and, in accordance with the requirements of the proposed rules, machined to the specified forms for tension tests of the joint and the weld-metal, a bend test of the joint, and a specific-gravity determination of the deposited metal. The procedure followed in fabricat- ing welded drums has been described at some length, because this process as applied to marine boilers is rela- FFICIAL adoption of the proposed new rules cover- ing marine boiler construction, now awaiting action by an ex- ecutive committee of the board of supervising inspectors, is ex- pected in the near future. What effect adoption of the new rules will have on the methods of marine boiler construction is dis- cussed in this article, the first part of which appeared in the June issue. tively new and is a subject of timely interest, in view of the fact that the use of welded drums probably will soon be authorized for merchant ves- sels. In 1930, the United States navy ordered the first boiler drums of fusion-welded construction, Previous to this time there had been carried out, in The Babcock & Wilcox plant alone, a most impressive program of research and experiment. Later, a wealth of experience was gained in o Physical _ test- ing laboratory fitted with mod- ern equipment for tensile, com pression and impact testing, also for heat treating @ ® The general an- alytical labora- tory. One of the important fac- tors in the con- trol of the qual- ity of materials used in boiler construction ® MARINE REVIEwW—July, 1934 the practical application of welding to boiler drums and pressure ves- sels for land service. To review these facts even briefly is to real- ize that fusion-welding has attained a new status and may be accepted by shipowners and operators as a modern construction that has been definitely proved to be safe and re- liable, and one that results in the production of drums that are lighter in weight and less liable to destruc- tion by caustic embrittlement than are riveted drums, Several Welding Processes The toregoing remarks on weld- ing apply to the use of the metal- are process only, but this company employs. for various spadeial pur- poses, almost every welding process except the forge-and-hammer meth- od, which it discarded in favor of other methods at the time of making an investigation of welding proc- esses. To be more specific, the list of methods used includes, besides the metal-arec process, gas welding, thermit welding, atomic-hydrogen welding, carbon-are welding, and both ‘‘flash”’ and ‘‘butt’” types of re- sistance welding. In this connection, it may be of interest to note that in the develop- ment of its flash-welding process, the Se company’s engineers joined together by this process, two lengths of 14- inch outside diameter pipe with 15/16-inch walls. The cross-sec- tional area of the metal of this weld- ed pipe is 89 times that of a l-inch outside diameter tube, 14-inch thick, an illustration of the tremendous strides made in the development of this process with respect to the size of the pipes that can be joined in this manner. Joining, by the flash-welding process, lengths of tubes for super- heaters, ewonomizers, and similar equipment is now common practice, In some cases, in the fabrication of superheaters, particularly for boiler 11