264 BELL SYSTEM TECIIXICAL JOIRSAL 



short liiiiu that the lu'ated pole butts will not he permitted to cool 

 when not immersed in oil. The oil change ordinaril\- is made in from 

 7 to 12 minutes from the time the pump starts to remove the hot oil 

 until the cold oil is up to the proper le\'el. 



Experience indicates that no material loss in penetration of the 

 creosote into the poles is experienced by having the treated section 

 imcoN'ered for this short length of time. Practically the same pene- 

 tration is obtained as would be secure<l by keeping the poles in hot 

 oil for the same length of time and then permitting the hot oil to 

 remain aroimd them until its temperature had ;j;racliiall\' fallen b\- 

 radiation to that specified for the cold oil bath. 



Changing the oil instead of permitting it to cool in the treating 

 tanks greatly expedites the treatments and conseciuently increases 

 the plant capacity, which, of course, results in a corresponding economy 

 in the cost of treating the poles. 



COXCI.U.SION 



In this paper an endeaxor has been made to co\'er in ,i i;cn(.ral way. 

 the principal engineering and operating features in\'ol\eil in building 

 creosoting plants designed specially for applying open tank treatment 

 to chestnut poles. It has, of course, been necessar\- to omit practically 

 all of the details of construction, which were followed in building 

 the various plants. 



These treating plants ari' valuable .ismIs lo iho Hell System in 

 providing concentration points where preser\ati\e treatment can 

 be economically applied to the chestnut poles, thus becoming an 

 important factor in the general program for the conser\-ation of 

 natural resources, by making possible the utilization of this valuable 

 and rapidly diminishing type of timber over a considerably longer 

 period. 



