SEISMIC METHODS 



871 



be borne in mind, however, that these products are designed to explode, 

 and that under suitable circumstances they will do so. 



Numerous protective devices for use in blasting have been developed 

 recently, to be employed as part of the circuit, blasting caps, igniters, or 

 primers, f 



The following rules have been found helpful in minimizing accidents : 



Trucks shall not carry more explosives than can be accommodated in 

 the magazines. Portable magazines are available and should be utilized 

 wherever permanent storage facilities cannot be provided. Not over three 

 persons shall ride in the explosives-carrying truck. 



Charges should not be made up prior to loading in shot hole. 



Caps and dynamite shall remain in magazines until ready for use. Old 

 dynamite should be used first. (It may be necessary to re-stow the maga- 

 zine when receiving delivery.) Dynamite should not be exposed to direct 

 rays of the sun for any long period. A complete and accurate inventory 

 should be maintained of explosives used and on hand. 



Personnel and equipment should maintain a 

 minimum distance of 100' from the shot hole while 

 firing. Charges must not be prepared by other than 

 a competent shooter. 



The firing line should not be longer than Y2 the 

 distance from the shot-hole to a high tension power 

 line. Extreme caution must be used in firing blast 

 phone shots. 



More than one charge should never be made up 

 at any one time. Never have more than one firing 

 line in use. 



After firing, firing leads shall be immediately 

 removed from blasting machine, shorted, and 

 stretched out on ground. Firing lines or sleeper 

 charges should be shorted and completely con- 

 cealed, to prevent inquisitive persons from finding the leads and conducting 

 experiments. Method of concealing firing line is illustrated in Figure 545. 



Misfire or delayed detonation should be given very careful considera- 

 tion. One hour should elapse before the hole is reloaded. Never remove 

 a misfire from the shot hole. 



No smoking must be allowed when handling explosives. 



No relaxation therefore should be permitted in the safety precautions 

 while explosives are being used. 



Carelessness seems not to be due primarily to failure on the part of the 

 man responsible to appreciate the hazards involved, but rather to be an 



t J. V. Hammond and D. J. Keenan, "Blasting Unit and Short-Circuiting Device," U. S. Pat- 

 ent 2,407,605, Sept. 10, 1946. 



H. J. Rolfes, "Means for Safeguarding Electric Igniters of Blasting Detonators Against 

 Accidental Firing," U. S. Patent 2,408,124, Sept. 24, 1946. 



H. B. Humphrey, "Safety Primer for Blasting," U. S. Patent 2,425,741, Aug. 19, 1947. 



B. L. Lubelsky and R. E. Hartline, "Protective Device for Blasting Circuits," U. S. Patent 

 2,428,334, Sept. 30, 1947. 



Fig. 545. — Safe practice in 

 loading. 



