TO SHIP CONSTRUCTION. 211 



clean, and that the wire flows smoothly and evenly through the arc without any 

 detrimental phenomena. 



All work should be examined and approved before welding commences in order 

 to see that the joints are properly prepared for the particular kind of weld to be 

 made, that the edges are properly fitted or spaced and the work properly closed up. 



In the thicker plates the first run of metal or "foundation" weld should be 

 made with a small wire, carefully examined for flaws or defects and passed upon 

 before the next layer of metal is added. This inspection should be carried out by 

 specially trained supervisors, who should also watch the welding in operation, check 

 up the current at the meters, and see that bad welds are cut out where required. 



The proportion of supervisors to operators will depend largely upon local con- 

 ditions, grouping and experience, but at present one supervisor to each six or eight 

 operators in the shop and one to each four or five operators in the field are being 

 tried. 



Various methods have been suggested for the inspection of completed welds, 

 and the Research Committee of the Welding Committee is at present investigating 

 a number of these, including electric resistance, magnetic. X-ray, and acoustic 

 methods, but the problem is extremely difficult and has not yet shown indication 

 of any satisfactory solution. 



In practice the usual tests applied are by blows from a hammer or by chipping 

 at intervals with a cold chisel or pneumatic tool. Either of these methods will 

 usually detect a really poor weld approaching zero efficiency, but neither can be 

 relied upon to indicate the value of a joint which, while not absolutely bad, does 

 not reach the standard of efficiency required in a particular case. For this reason 

 it is most necessary to rigidly test every material and system of welding proposed be- 

 fore accepting them as suitable for application to important strength members. 



PRESENT APPLICATION OF ELECTRIC ARC WELDING IN SHIP REPAIR WORK AND NEW 



CONSTRUCTION. 



The range of application of the arc-welding process to the execution of marine 

 repairs such as the reclamation of broken castings, fractured plates, boiler furnaces 

 and the reinforcement of eroded or badly wasted plate edges and cracked hull 

 plates is so well known and so varied that only the briefest mention is possible within 

 the scope of this paper. A few instances of such application are illustrated in 

 Plates 141 to 143. 



Plate 141 shows a repair which was successfully carried out to a broken stern 

 frame gudgeon on a small steamer. The repair was effected in place and obviated 

 the delay and expense of a new stern frame. 



Plate 142 shows a method of reinforcing a badly eroded propeller strut and worn 

 bossing. This repair occupied four days and the saving in time and expense com- 

 pared with that of furnishing a new casting is obvious. 



Plate 143 illustrates a salvage operation to fractured end keel nlates necessi- 

 tating ovei-head welding. 



