Rand.] -^1" [Jan. 7, 



Note on the Protection of Oil Tanks from Lightning Strolce. By B. 

 Hoicard Band, M.JD. 



(Bead before the American PMlsophieal Society, January 7, 1881.) 



The frequency of the ignitions of the contents of tanlis used for storing 

 mineral oil, with tlie concomitant destruction of property and life has at- 

 tracted much attention. The suggestions as to the means of prevention 

 have been crude. 



It is my purpose to offer a theory as to the cause, and a means of avoid- 

 ing the mischief 



An air-tight tank of metal, or one sheathed with metal, would, if 

 filled with crude rock-oil, or even with loose gunpowder, be safe from 

 damage from lightning stroke. It would be no more in danger of the 

 thunderbolt than a log-cabin similarly situated. If struck it would escape 

 unharmed. Tlie late Professor Clerk Maxwell suggested the protection of 

 powder-magazines by sheathing them with metal. Professor Tait recom- 

 mends the investigator of the so-called ball or globe-lightning to wear a 

 suit of light copper armor. It would be safer to add a thorough ground 

 connection. This could be made in most cases to the pipes. 



As the level of the oil in the tanks must vary with the rate of the inflow 

 and outflow through the pipes, openings are necessary to allow the egress 

 or ingress of air. There may be occasion to lift the lid at times. 



From the necessary openings and leaks around the lids, the light hydro- 

 carbon vapours escape. These mingling with the air form an explosive 

 mixture like the fire-damp of mines, which, if ignited at a distance of even 

 hundreds of feet, will travel back and set fire to the contents of the tank. 



To prevent this I suggest that the necessary vent-holes be protected with 

 safety tubes after the plan of Hemming's, or with several layers of fine wire 

 gauze, strong enough to resist any probable breaking by mechanical shock. 

 These should be protected from dust and wet by loosely fitting covers. 



On the approach of a thunder-storm, the outflow should be checked, so 

 as to avoid an indraught, which we so well know will render useless in 

 many cases the protecting metallic mesh. 



Where moveable covers are used, they should have the ordinary seal 

 used in telescopic gas-holders. Glycerine in the seal is recommended as it 

 does not evaporate and is not affected by changes of temperature within 

 the limits of ordinary atmospheric fluctuations. 



Where it is necessary to introduce chemical agents in the process of re- 

 fining, the well known safety traps should be used. 



