THE OXYHYDRIC PROCESS 79 



In welding, one part of oxygen to from four to six parts 

 of hydrogen are used, and it is necessary to obtain a com- 

 plete absorption of the oxygen, by the hydrogen in excess, 

 in order to make a perfectly homogeneous flame. This was 

 a difficult problem to solve as the fear of explosion long 

 prevented the mixing of the two gases before their in- 

 flammation. 



It was overcome by assuring to the mixture of the gases 

 a velocity greater than the velocity of the propagation of 

 the flame, as an explosive mixture contained in a tube does 

 not ignite instantaneously in all of its mass when combus- 

 tion is started at one end of the tube. 



The ignition is propagated in the tube with a finite 

 velocity which increases as the square of the section 

 thereof. If, therefore, the gaseous mass moves toward 

 the point of ignition with a speed greater than the speed 

 of propagation, the flame will not reach the inside of the 

 torch and much less that of the mixer. 



Thus, having obtained a minimum for the speed to be 

 given the gas, it is necessary not to exceed the maximum, 

 and this is obtained by a practical consideration, namely, 

 that the jet of gas leaving the torch must not be strong 

 enough to set in motion the drops of the metal which are 

 intended to constitute the weld. 



In operation the two gases are carried from the steel 

 bottles to the mixer where they are mixed as previously 

 described from the cutting operation. From the mixer 

 they are carried to the torch through a single tube and 

 enter this where there is a sharp enlargement in its shape. 

 This considerably diminishes the velocity of the gases, and 

 from there they pass through a conical tube that is per- 

 fectly smooth on the inside. This tube gradually dimin- 

 ishes in size down to the nozzle, and the speed of the gases 

 gradually increases again until the minimum speed required 

 is obtained. 



As a sample of some of the fine work which can be done 

 by welding with the oxyhydric process, Fig. 10 shows an arl 



