The Relation Between Penetration and Decay 

 in Creosoted Southern Pine Poles 



By R. H. COLLEY and C. H. AM ADO N 



Poor penetration of the non-durable sapwood is the most important 

 factor in the decay of creosoted southern pine poles. Over 3000 such poles 

 that had been treated with coal tar creosotes of varying types at thirteen 

 creosoting plants in the South have been critically inspected to determine 

 when and where decay started. The poles had been in line from five to 

 twenty-six years under widely diverse climatic conditions in scattered 

 localities east of the Mississippi River. Ninety-five per cent of the failures 

 were poles in which the creosote had penetrated less than 1.8 inches and 60 

 percent of the sapwood thickness. No failures were found in poles that had 

 Ijeen penetrated more than 2.1 inches and 75 per cent of the sapwood 

 thickness. The current Bell System treating specifications require a 

 penetration of 2.5 inches or 85 per cent of the sapwood thickness. The 

 hazard of failure by decay during the ordinary service life of a line is reduced 

 to a practical minimum in poles produced under these specifications. 



Introduction 

 ^ I ^HE creosoted southern pine pole has been justly regarded as a 

 -*- long-lived unit of plant equipment. However, there have been 

 enough instances of failure by internal decay during the first few 

 years in line to focus attention on the poorer poles and to raise questions 

 about the quality and probable length of service of creosoted poles in 

 general. The data presented in this paper were obtained in the 

 course of an investigation to determine how, when, and where decay 

 starts in creosoted southern pine poles in line, and what proportion of 

 the poles are decaying after different periods of service. The results 

 of the study are of particular significance as a basis for engineering 

 the treatment of poles in a satisfactory and economic manner. 



General Conclusions About Decay in Poles in Line 

 In the sections of the lines that were inspected the incidence of 

 decay was definitely correlated with the depth of penetration of the 

 creosote and the per cent of sapwood penetrated. 



When all of the 3102 inspected poles of all ages up to 26 years were 

 taken together: 



(a) There were 62 failures, all of which had penetration less than 2.1 



inches and 75 per cent of the sapwood thickness; and the 62 



failures were 2.00 per cent of the total poles inspected; and 



(6) Of these failures 59, or 95.16 per cent, had penetration less than 



1.8 inches and 60 per cent of the sapwood thickness. 



All the field evidence indicates that the inspected poles, when the 



sapwood had been well penetrated with creosote, were practically 



immune to destruction by wood-destroying fungi for a long time. It 



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