252 



BELL SYSTEM JECILMCAL JUL KX.U. 



Treatmknt 



The following is a very brief outline of tlie nuiliod pur? 

 treating the poles and also of the results obtainetl. 



In so far as practical >lr the poles are seasoned (i niontiis ( 

 before being treated. Tiic niciliod of treatment coiisisis 

 mersing llic butts to a U'\il nf .ihout 1 fool alioxc what will 



r more 



of ini- 

 \<v ihc 



Fig. 20 — IVe[)aralion Skids Opposite Treating Tanks in Nashville N'ard 



ground line nf liic |)oles, for not less than 7 hours in crcosoic at a 

 temperature between 212° and 2;^0° Fahrenluil. .\l the end of the 

 hot treatment, the hot oil is ciuickK- removed irnni tiu' lank and cold 

 oil at a temperature of from 100° lo 11()~ Fahrciiiicii is perniitled to 

 flow quickly into the treating tank lo liu' lc\cl [)it\iously readied 

 by the hot oil. The cold oil trealincMl hisls for al least I hours. 



Heat is absorbed b\- the p<<\v Initts in the iiol oil bctlii tiiilil the 

 moisture contained in the sa|)wood is either e.\i)anded into steam or 

 entirely driven out. DiUMUg the short interval while the oil is being 

 changed, the surfaces to be treated remain covered In- oil from the 

 hot treatment. The oil change is made so C|uickl\ tiiit tin- pole 

 butts cof)l verv' little before it is completed. Then, as soon as the 

 cold oil is admitted, these surfaces are covered by the creosote which 

 reuKiins until the pole butts become cool. In the sapwood, from 

 which the moisture has been driven by the hot treatment, the cooling 

 [)rocess condenses the steam, thus forming a partial vactium in the 



