Update On Copper Naphthenate Tie Research (cont)

Three sections of ties were also dipped with borates followed by air seasoning prior to further treatment with preservatives. Two groups of the borate dipped crossties were treated with secondary treatments of copper naphthenate and creosote. One small test group of crossties (10 ties) was borate dipped only with no secondary preservative treatment. Sections 3, 4 and 5 in the test track contain the borate dip treated crossties. Timbor™ (U. S. Borax, Inc.) solution (32% concentration) was used to pre-treat green ties, using specific gravity tests and air agitation to insure proper solution strength and mixture of solution. While maintaining temperature between 135-150° F., two ties were dipped for two minutes. Dipped ties were then bundled together in plastic for 90 days to reduce moisture loss and aid in the diffusion of the borate into the wood.

As previously indicated, the location of the test track is in Lewistown, PA on the old Conrail system (now Norfolk-Southern). Specifically the test site is located on #2 track of the Harrisburg to Pittsburgh mainline between milepost 165.2 and 165.5, with a slight grade of 0.46%. This line was rated at ~34 MGT at the time of installation but has now increased to ~55 MGT. Part of the test section consists of a 6°49’ curve, mostly in sections 2-6 (Figure 6) containing the copper naphthenate and borate-treated ties. Installation of the test crossties took place August 22^nd and 23^rd in 1988.

Inspection Of The Test Crossties

The last inspection of these test ties occurred in 1990. Since that inspection the railroad has changed ownership from Conrail to Norfolk Southern, and Mooney Chemical Company (now OM Group) no longer produces copper naphthenate for use in the pressure treated wood preservation industry.

Within the past several years Merichem Company, the world’s largest producer of naphthenic acid, has started producing and actively promoting copper naphthenate for the pressure treated wood preservation industry. Merichem received permission from OMG to obtain and reference many of Mooney’s research tests that involved treated wood products, including the test site for crossties at Lewistown, PA.

Even though it had been approximately ten years since the Lewistown site was last inspected, it was determined that some valuable information could be obtained by conducting another inspection, particularly in light of the railroads’ recent requests to RTA for alternatives to creosote. During the later part of June, 2001 a team of four individuals conducted an inspection of the crossties at the Lewistown site. Those involved with inspection were Jim Brient of Merichem Company; Harry Bressler and Jim August of Burke-Parsons-Bowlby, and Dave Webb, consultant and representing the Railway Tie Association and its Research and Development Committee.

The inspection consisted of the following procedures:

• Note and record number of crossties remaining in the test for each type of treatment. It was observed that many of the original metal tags were still place on the test ties.
• Physically measure the checks and splits in the ties. The RTA Tie Gauge (Figure 7) was used to measure the depth and width of the checks and splits; while a tape measure was used to measure the length. This information was recorded in a notebook for each tie. Following the inspection, the average volume (as cubic inches) for the void space was calculated from these field measurements and recorded.
• Measurements were taken and recorded for plate cutting.
• Each tie was given a rating according to its performance and observed by the number of checks, splits and their severity. This was a visual observation following the guidelines for evaluating wood preservatives in a soil bed in American Wood-Preservers’ Association Standard E14-94, with the subjective rating scheme as follows:

With four individuals performing the inspection, it was possible to work in teams of two, both grading the ties with one recording and the other taking measurements on each crosstie. The inspection of all nine hundred and twenty-three (923) ties was completed in approximately one and a half days.

Results of the Inspection

The tabular results of the inspection are given in Table III and shown in Figure 8. The average rating of all ties in the test was 8.66, with ± one standard deviation ranging from 9.59 to 7.73. Except for the borate dip-only ties, all combinations of preservative and seasoning regimens fell within one standard deviation of the mean rating for all ties, indicating there was no significant difference in performance after 13 years in those preservatives and treating schemes. The small (10) number of borate-dip only ties makes suspect any conclusions drawn about the performance of that treatment relative to the other treatments.

It was determined part way through the inspection of the Section No. 2 (copper naphthenate air seasoned ties) that a number of new ties had been installed. Discussions with Norfolk Southern track personnel indicated that new creosote treated crossties were randomly inserted in the test track in July of 1998. In Section 7 (Boulton seasoned creosote) no crossties had been replaced. However, only sixty-seven (67) ties were graded and considered part of the test due to the presence of a grease box (for rail/wheel lubrication) located at the end of the test section, which influenced the results. Thirty-three (33) ties were completely covered with grease and thus not graded.

In Section 6, which consisted of four hundred and two (402) crossties, each tie was given a rating; however, only ever fourth crosstie was measured for the length, depth and width of the checks and splits using the RTA gauge. Originally there had been ten (10) crossties in the test given the borate dip treatment, and two of these had been replaced. There were too few ties to reach any conclusion about this treatment.

Ties given a borate dip pretreatment followed by secondary treatment with copper naphthenate or creosote had the greatest void volume due to splits and checks after 13 years of exposure (Table III). On the other hand, ties treated with a borate dip only had the lowest average void volume results, although they had the most “weathered” appearance in terms of rounded-off edges, as seen when comparing Figure 9, Figure 10 and Figure 11. This appears to confirm the statement by Webb (1991) that a certain degree of weather protection is provided by a creosote and/or oil type treatment that is not provided by waterborne preservatives.

There was not a significant amount of plate-cutting on any the test ties, less than the thickness of the tie plate. In fact, after initially taking some measurements in Sections 1 and 2, it was decided to not continue taking them. Where plate-cutting did occur it was simply noted in the field notebook. No significant differences were seen in the extent of plate cutting between the various preservative treatments. Several ties were noted to have both clip- and spike-type fasteners.

Summary of the Results

The crossties at time of inspection had been in test for thirteen (13) years. The following summary of the results were made from the inspection of the test ties:

• As a general observation the crossties remaining in the test are supporting the track system and giving satisfactory performance.
• There did not appear to be a significant difference between the performance of the creosote and copper naphthenate (CuN) treatments.
• In addition, similar performance was noted between the air seasoned and Boulton seasoned crossties.
• With regard to the ties in Sections 3 and 5, borate dipped followed by a secondary copper naphthenate and creosote treatment, respectively, both groups of ties showed the highest level of “checks & splits” as measured by average void volume but otherwise performed adequately.
• Too few ties, only ten (10) originally, were in the test to make any judgment on the performance of crossties that were borate dipped with no other treatment.

References Cited

1. Barnes, H. M.; Amburgey, T.L.; Freeman, M.H.; Brient, J.A. 2001. Performance Of Copper Naphthenate-Treated Hardwoods, International Research Group – Wood Preservation, 32nd Annual Meeting, Nara, Japan, 20-25 May 2000. Document No. IRG/WP/01-30269.
2. Brient, J. A.; Wessner, P. J.; Doyle, M. N. 1995. Naphthenic Acids, In: Kirk-Othmer Encyclopedia of Chemical Technology. New York: John Wiley & Sons.
3. Kamdem, D. P.; Gruber, K.; Freeman, M. 1995. Laboratory evaluation of the decay resistance of red oak (Quercus rubra) pressure treated with copper naphthenate. Forest Prod. J. 45(9): 74-76.
4. Kamdem, D. P.; Chow, P. 1999. The effect of pressure on the retention and bending properties of copper naphthenate and CCA type C treated hardwoods. Wood & Fiber Science, 31(2): 128-135.
5. McIntyre, C. R. 2001. Summary Report on Copper Naphthenate Performance in AREA Stake Tests. RTA Wood Preservative Technology/ Methodology Task Force Meeting, Perdido Beach, AL.
6. Minich, A.; Goll, M. 1948. The technical aspects of copper naphthenate as a wood preserving chemical. In: Proc. American Wood Preservers’ Assoc. 44:82-81.
7. Webb, D. A. 1991. Wood Preservative Treatments for Crossties and Potential Future Treatments. Crossties, December 1990/January 1991.

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