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idly reduced life of each of the bricks. (b) Sudden demands for steam by the main engines must be met by rapid changes in the rate of steam evaporation in the boiler with a cor- responding rapid change in the fur- nace temperature. This is particular- ly true with oil fired boilers. The ef- fect of these changes can be somewhat controlled by the chief engineer with a well indoctrinated crew by instruct- ing them in the care that must be used in operating the main throttles. Except in emergencies throttles should be carefully opened and closed and the throttlemen should be so trained. Rapidly opening or closing the throttles builds up or draws out steam in the boilers in rapid fluctua- tions which must be met by rapidly changing the firing rates. Rapid changes in the firing rates not only results in the loss of the heat balance on which economical steaming is dependent, but, in addi- tion, it introduces thermal shock in the refractory brick which may result in the development of spalling cracks. In any change of firing rate the air- fuel ratio, which it is assumed is properly balanced, is varied. This results in a change in the atmospheric conditions in the furnace which may become either oxidizing or reducing with the corresponding ill effect on the brick. Hence, whenever a change in the ship’s speed is made, care must be exercised to bring the firing opera- tions to the new conditions as quickly and as equally as possible. Direction of Flame in Boilers (c) As the brick work in an oil fired boiler is probably under more strenuous operating conditions than in coal fired boilers, the general dis- cussion of brick failure hinges more on the ability of a brick to stand up in an oil fired boiler, and it may be safely assumed that a brick which will give good service in that type of boiler will give equally as good or better service in a coal burning boil- er. A brick being played upon by an oil spray will soon fail due to erosion of the brick from the force of the spray and the impregnation of the brick with oil which will probably act as a flux and lower the fusion point of the brick. The location of the tip in the burner, the adjustment of the burner, and the oil pressure are contributing causes for oil spraying on the furnace brick. Alteration of any one or all will probably result in proper flame direction. The large fur- nace volumes available in shore boil- ers which will give sufficient room for the oil fog to completely burn without impingement on the heated Surfaces cannot always be obtained in marine boilers. For this reason greater care in adjustment and opera- tion is essential. (d) An excess of air in a furnace results in an oxidizing atmosphere; an insufficiency of air results in a re- ducing atmosphere. Certain mate- rials in the brick fuse more readily than other materials when either of these conditions exist. A reducing atmosphere results in the more rapid formation of a flux from the impuri- ties and oxides in the brick, and when that condition occurs, soften- ing and fusion will possibly follow. In addition to being the more efti- cient steaming condition from the standpoint of fuel economy, which re- quiries a minimum of excess air com- . patible with complete combustion of the fuel, any deviation from the prop- er air-fuel ratio will have a harm- ful effect on the brick work. (e). The ash from certain coals have ingredients which act as a flux and form a slag of the melted ashes. These fluxes are sulphur and iron in the form of pyrites in the coal as well as certain alkaline earths. If the slag from these impurities is carried into contact with the _ refractories, softening of an otherwise good fusion resisting brick will result. Coal, low in sulphur content, is desirable; and clinkers and ashes should be care- fully and frequently removed .on ac- count of the possible detrimental af- fect on the brick work, as well as the effect on the boiler’s economy. (f) In addition to reducing the overall boiler efficiency, dirty boiler tubes have a decidedly detrimental effect on the boiler brick. As dirty tubes reduce heat transference from the gases to the water to generate an equal amount of steam, the condition is somewhat analogous to that en- countered in higher rates of steam- ing, in that greater furnace tempera- tures are required for the same tem- perature on the water side of the tubes. These higher temperatures re- duce the life of the brick work pro- portionally. As the ill effects of dirty tubes are most noticeable in the MARINE REview—April, 1931 Fig. 5—Poor quality fire clay with low softening temperature. ‘ure. boiler economy, it is presumed that the vigilant chief engineer will nat- urally avoid steaming with dirty tubes as much as _ possible. (g) Whether through bolt holes, poor joints, cracks, or other means of ingress, air leaks into the fire box have a destructive effect on the brick work by setting up unequal stresses. These unequal stresses result in the formation of spalling cracks, and must be avoided. They can be elim- inated to a great degree by proper attention to the face of the brick walls, filling up such cracks as de- velop, tightening bolts, and ensuring the absence of air leaks. (h) Vibration is much more fre- quently encountered aboard ship than ashore, and, in general, is of a more serious nature and probably of more serious consequence. It may be due to a number of causes; the ordinary Good fire brick vibration from the machinery in use; the vibration from a propeller out of balance, or bent line shafting. Or, it may be due to the boiler panting. Of all the possible causes, panting has probably the most disastrous effect on the brick wall, reaching, in the ulti- mate case, the condition where the brick wall may be thrown down and absolutely destroyed. Panting will probably occur more frequently in firerooms under forced draft, partic- ularly when the ship is maneuvering and rapid fluctuations in firing rates are required to meet the varying steam demands. Panting is a result of an improper air-fuel ratio and can only be offset by the proper training and the vigilance of the fireroom personnel. . The operating factors, in general, which have a detrimental effect on the life of a boiler furnace lining can be greatly overcome by proper atten- tion to the details of fireroom proced- At each opportunity the fire sides of boilers should be inspected. 79