When a tube sheet blisters, the defective part must be cut out by hand-tapped holes drilled by ratchets and as it is frequently impossible to get space in which to drive rivets, a "soft patch" is necessary. This is but a makeshift at best and usually results in either a reduction of the safe working pressure or in the necessity for a new plate. If the latter course is followed, the old plate must be cut out, a new one scribed to place to locate rivet holes and in order to obtain room for driving rivets, the boiler will have to be re-tubed. The setting must, of course, be at least partially torn out and replaced. In case of repairs, of such nature in fire-tube boilers, the working pressure of such repaired boilers will frequently be lowered by the insurance companies when the boiler is again placed in service. In the case of a rupture in a water-tube boiler, the loss will ordinarily be limited to one or two tubes which can be readily replaced. The fire-tube boiler will be so completely demolished that the question of repairs will be shifted from the boiler to the surrounding property, the damage to which will usually exceed many times the cost of a boiler of a type which would have eliminated the possibility of a disastrous explosion. In considering the proper repair cost of the two types of boilers, the fact should not be overlooked that it is poor economy to invest large sums in equipment that, through a possible accident to the boiler may be wholly destroyed or so damaged that the cost of repairs, together with the loss of time while such repairs are being made, would purchase boilers of absolute safety and leave a large margin beside. The possibility of loss of human life should also be considered, though this may seem a far cry from the question of repair costs. Space Occupied--The space required for the boilers in a plant often exceeds the requirements for the remainder of the plant equipment. Any saving of space in a boiler room will be a large factor in reducing the cost of real estate and of the building. Even when the boiler plant is comparatively small, the saving in space frequently will amount to a considerable percentage of the cost of the boilers. Table 2 shows the difference in floor space occupied by fire-tube boilers and Babcock & Wilcox boilers of the same capacity, the latter being taken as representing the water-tube class. This saving in space will increase with the size of the plant for the reason that large size boiler units while common in water-tube practice are impracticable in fire-tube practice. TABLE 2 COMPARATIVE APPROXIMATE FLOOR SPACE OCCUPIED BY BABCOCK & WILCOX AND H. R. T. BOILERS