AMERICAN SOCIETY OF CIVIL ENGINEERS
INSTITUTED 1852
TRANSACTIONS
Paper No. 1168
TESTS OF CREOSOTED TIMBER.
By W. B. Gregory, M. Am. Soc. C. E.
During the last few years a quantity of literature has appearedin which the treatment of timber by preservatives has been discussed.The properties of timber, both treated and untreated, have beendetermined by the Forest Service, United States Department of Agriculture,and through its researches valuable knowledge has come toengineers who have to deal with the design of wooden structures. Thereis very little information, however, regarding the effect of time oncreosoted timber, and for this reason the results given herewith mayprove of interest.
The material tested consisted of southern pine stringers having across-section approximately 6 by 16 in. and a length of 30 ft. Forthe purpose of testing, each beam was cut into two parts, each about15 ft. long. This material had been in use in a trestle of a railroadnear New Orleans for 26 years. The stringers were chosen at randomto determine the general condition of the trestle. The timber had beenexposed to the weather and subjected to heavy train service from thetime it was treated until it was tested. The annual rainfall at NewOrleans is about 60 in., and the humidity of the air is high. In spiteof these conditions, there was no appearance of decay on any of thespecimens tested. The specifications under which the timber wastreated were as follows:
Timber.
The timber for creosoting shall be long-leafed or southern pine.Sap surfaces on two or more sides are preferred.
[38]Piles.—The piles shall be of long-leafed or southern pine, not lessthan 14 in. at the butt. They shall be free from defects impairingtheir strength, and shall be reasonably straight.
The piles shall be cleanly peeled, no inner skin being left on them.The oil used shall be so-called creosote oil, from London, England, andshall be of a heavy quality.
The treatment will vary according to the dimensions of the timbersand length of time they have been cut. Timbers of large and smalldimensions shall not be treated in the same charge, neither shall timbersof differing stages of air seasoning, or the close-grained, be treatedin the same charge with coarse or open-grained timbers.
The timbers shall be subjected first to live steam superheated tofrom 250 to 275° Fahr., and under a 30 to 40-lb. pressure. The livesteam shall be admitted into the cylinders through perforated steampipes, and the temperature shall be obtained by using superheatedsteam in closed pipes in the cylinders.
The length of time this steaming shall last will depend on thesize of the timbers and the length of time they have been cut. In pilesand large timbers freshly cut, as long a time as 12 hours may berequired. After the steaming is accomplished, the live steam shall beshut off and the superheated steam shall be maintained at a temperatureof 160° or more and a vacuum of from 20 to 25 in. shall be heldfor 4 hours or longer, if the discharge from the pumps indicates thenecessity.
Oil Treatment.—The temperature being maintained at 160° Fahr.,the cylinders shall be promptly filled with creosote oil at a temperatureas high as practicable (about 100° Fahr.). The oil shall be maintainedat a pressure ranging from 100 to 120 lb., as experience and measurementsmust determine the length of time the oil treatment shall continue,so that the required amount of oil may be injected.
After the required amount of oil is in