BRIDGE SHOPS AND SHOP PRAC TICE. The working plant of a bridge build ing company is composed of shops and depart ments so arranged in their relation to each other that the movement of the material handled by them is continuous and in one direc tion — the rough material entering at one end of the plant and passing out as a finished prod uct at the other. This arrangement ensures the reduction to a minimum the time lost in handling, and also the greatest possible economy in the cost of production.
Each of these shops is under the immediate charge of a foreman or superintendent who re ports daily to the general superintendent or manager of the plant, who makes out the pro gram of work, and prescribes the dates upon which the different pieces of work are expected to be completed, the desideratum being to keep the various shops continually working, and to complete the various parts of the bridges in the order in which they are required at the place of erection.
The buildings of the various shops are usu ally of fireproof construction and conform to the requirements of larger size, good lighting, heat ing and ventilation. They are connected by narrow-gauge railway tracks, which run length wise through them so as to facilitate the trans portation of the material from one part of the works to another with the least amount of handling. Ample yard-room is provided at the ends of the buildings and also around them for the storage of partially completed material awaiting its turn for the finishing touches before shipment. These yards are usually laid out so that the carrying distance is as short as possi ble, and the work of carrying is accomplished by overhead traveling cranes.
These shops may be designated and described as follows: (1) Power Plant,' consisting of large bat teries of boilers for generating steam, and en gines for driving the dynamos through which power and light are furnished to all parts'of the works, and other engines for operating the air compressors which furnish the power for the portable pneumatic drills, riveters, hammers and reamers, and also the compressed air used for the draft of rivet furnaces, and blacksmith forges; for the cleaning of finished material, and for painting them by means of spraying devices.
In some cases, the hydraulic pumps and ac cumulators which supply the water to the hy draulic presses and riveters are also located in the buildings of the power plant, all the machinery of which is installed in duplicate so that an accident would not necessitate the shutting down of the entire plant during the time consumed in making repairs.
Although the first cost of a centralized power plant is comparatively high, its advan tages over that of a scattered system may be briefly summed up as follows: Cheap grades of fuel may be used under the boilers, and mechanical stokers may be employed and thus reduce the number of firemen required by the several boilers of the scattered plants. The number of engine attendants is also greatly re duced, their places being filled by a few elec tricians to keep the wiring and motors in work ing condition. The power may be. transmitted to every part of the plant with the smallest amount of loss.
(2) °Receiving Yard,' where the material for each bridge is properly selected, classified and stored.
(3) Department,' where the irregularities in the material, due to the short comings of the rolling mill processes, are cor rected by more accurate methods. The buckles in the plates and the deviations from true alignment in the plates are eradicated by pass ing them through a series of rolls usually con sisting of six sets. These rolls are so arranged that the vertical distance between them can be made less at one end than at the other, so that by passing a plate through them several times, it can be stretched unequally and any imper fections in the alignment of its edges thus corrected. Beams, channels, Z-bars and other odd shapes are best straightened by the applica tion of local pressure to the parts out of line either by screw presses, or by the action of a plunger operated by a power-driven cam. Badly sprung shapes and plates may be straightened by being hammered cold, or after being heated; it is, however, very destructive to the material and dangerous to put into actual use.