250 COST ACCOUNTING AND ESTIMATING. 



theoretical calculation by which sizes are determined; second, tabulate from practice the 

 various sizes; third, apply the theoretical calculations and from practice obtain the coeffi- 

 cient so that the result may coincide with those usually adopted; fourth, calculate and tabu- 

 late results throughout the entire range of requirements. A few examples are as follows: 



The size of the circulating pump depends upon the amount of steam to be condensed, 

 the temperature of the sea water, the vacuum, and the percentage of the rated capacity of 

 the pump in actual service. After having determined the amount of steam used by the vari- 

 ous types of engines, the amount of water required by the theoretical calculation is deter- 

 mined and this amount compared with the rated capacity of the pump indicating that, in 

 normal running condition, the pump is working at a certain percentage of its rated capa- 

 city. Tabular statements are then prepared for several temperatures of sea water and for 

 predetermined water rates and vacuums for the several types of engines. Without calcu- 

 lation it is then possible to ascertain from this tabulation the normal size of a circulating 

 pump for compound, triple, quadruple, turbine or electric drive, for several temperatures 

 of sea water, the instructions giving the temperature to be used for the various routes. 



The same method applies equally well to the hull jobs. In anchor gear, for instance, 

 the size of the hawse pipe must be sufficient to prevent the chain shackles from fouling 

 under all conditions. From practice, the clearance over the diagonal length of the chain 

 shackle is plotted, to which is added the diagonal length of the shackle for determining the 

 diameter of the hawse pipe. The length of the hawse pipe must be sufficient to permit of the 

 proper housing of the stockless anchor. The top and bottom thicknesses and the dimensions 

 of the lips are plotted from practice. With the standardized dimensions, hawse pipes are de- 

 tennined for all sizes of chains and the weights calculated. The dimensions of chain pipes, 

 devil claws, cable clenches, hawse-pipe covers and anchor davits are similarly determined 

 and placed in tabular form. The weights and costs throughout the entire range are care- 

 fully calculated and tabulated, so that for any size vessel or any size chain the weights 

 and standard costs of not only the above fittings but the windlasses, anchors and chains 

 themselves can be immediately obtained either in detail or in total. 



A brief description of the method of applying the standardized information is given 

 by an example for determining the size of the main engine when not specified. A tabular 

 statement is prepared, giving the minimum, normal and maximum horse-power ; the size 

 of the engine; the minimum, normal and maximum revolutions; together with reference 

 plans, hull numbers, and condition of patterns for the various engines constructed, with 

 intermediate sizes where the sizes constructed are not sufficient to cover the entire range of 

 horse-powers. Based on propeller performance, a tabular statement is prepared, giving the 

 normal revolutions for varying speeds and drafts. Following the direction of the typewritten 

 instructions, it is merely necessary to ascertain from the latter table the normal revolutions 

 for any given draught and speed, and from the tabular statement of engines pick out the 

 proper size. Reference is then made to a weight and cost folder for this particular size 

 of engine, from which can be obtained at once the total net weight, the total gross weight, 

 the standard cost of material and hours of labor. Current cost is obtained from the above 

 by factors. 



Similarly, the proper size of the condenser may be determined, and reference is made 

 to the weight and cost folder which contains a list of condensers advanced by intervals 

 of 100 square feet. This is accomplished by increasing or decreasing the length of the 

 condensers actually constructed. The weights and costs are carefully calculated from bills 



