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Roe ts efractory Brick in Marine Boilers Severe Operating Condition s—Selecting Brick of Good Grade and Quality—Care in Laying Wall—Reduction in Maintenance Costs EVELOPMENT in boiler de- D sign has proven the usefulness of large furnace volumes for complete combustion of the fuel be- fore the burning gases strike the heated surfaces. In order that the gases of combustion be maintained at the proper high temperatures for complete combustion, it is essential that reflecting surfaces be provided. These reflecting surfaces are the fur- nace linings which serve the dual purpose of containing the heat with- in the boiler, providing the radiat- ing walls, and consist of a wall of refractory material backed by a sec- ond wall of insulation. In general, similar problems and considerations in lining a boiler fur- nace apply to both marine and land installations. Central station plants ashore are comparable to the boiler installations found aboard ship. In practically all respects, however, ex- cept for occasional higher temper- atures encountered, and the de- formation of the brick under the load of its own weight in a high wall, marine boiler brick must withstand more severe operating conditions. Notable among those’ conditions where marine installations are con- The second and concluding install- ment of Lieutenant Griffith’s article on the selection, laying and care of fire brick in marine boilers will appear in the April issue. Part | By Lieut. C. A. Griffiths, U. S. Navy fronted with more severe conditions than are encountered ashore are: High and unequal rates of firing; the vibration encountered; the tend- ency of the furnace gases to pro- duce a reducing atmosphere; the working of boiler parts that will occur in a sea way; the rigidity of construction required in boiler cas- _ ings and supports; the necessity of carefully anchoring each brick to the boiler casing to prevent the wall fall- ing or bulging in heavy weather; and, the limitations generally placed on weight and space. Sustained Reliability and Economy The two essential considerations in marine boiler linings are sustained reliability and economy. Reliability is absolutely essential, for, on the wall, may depend the safety of the ship itself; a failure at sea may ne- cessitate shutting down a boiler, loss of steam, and, ultimately, disaster. Economy, in a way, is closely re- lated to reliability in that a sched- uled sailing might not be met on account of a sudden failure of a wall. True economy, however, is logically divided into headings: (1) The effect of the boiler steaming efficiency, and (2) The effect of the general maintenance expenses. A poorly layed up wall or a wall of in- ferior material will soon develop air leaks which will destroy the boiler Fig. 1—Furnace wall after oil fired to 8000 degre - carefully made up, smooth face, thin even ues Bontuns 20 Excellent grade of brick property of clay excellent MARINE REVIEW—March, 1931 efficiency by increasing the excess air content of the flue gases and in- crease radiation losses by a reduc- tion of the wall’s refractoriness, It is in reducing the general main- tenance costs, however, that the greatest improvements in economy are possible. Maintenance costs depend egsen- tially on the life of the brick wall. The three major factors which affect the life of the wall are: (1) Method of laying up the wall. (2) Grade and quality of brick used. (3) Character of boiler operation. Each of these major factors are further subdivided into separate con- siderations which will become of greater importance in proportion as the operating personnel fails to abide by the rules of good engineering practice. The objectives in all main- tenance problems are obviously: To reduce repair bills; to reduce the length of the stay of the ship in port; eliminate overtime labor; and, to increase the operating periods be- tween overhauls to a maximum con- sistent with economical operation. Repair yards, with the skilled la- bor at their command, are well pre- pared to rebrick a boiler with the minimum possible delay. However, no matter how carefully a wall is made up, no matter how excellent is the grade of brick used, the life of the wall will be materially shortened by carelessness in operation and lack of attention by the operating personnel. Failure of a wall may occur in a port not equipped with the necessary yard repair facilities; or it may OC cure at sea, and under such condi- tions it behooves the chief engineer to know exactly what to do and how to do it. In addition to the knowl- edge necessary to care for the in- frequent emergencies which may ar- rive, the chief engineer should real- ize the various factors which enter into the life of a brick wall in order that by careful supervision he may reduce the maintenance expenses of his ship. For it is only by the re- duction of the operating costs to the absolutely minimum that steam- ships can successfully compete with motor vessels and not show a bal- ance ‘‘in the red.’’ The standard fire brick is 9 x 4% x 2% inches. Where the require-