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create problems with a number of
<br />tests. The rough orange peel surface
<br />tends to retain moisture which will
<br />cause significant problems, especially
<br />with holiday detection.
<br />Until proven otherwise, surface ap-
<br />pearance problems should be consid-
<br />ered indicative of an unacceptable
<br />coating. The powders stored at 41° C.
<br />and 23° C., 95% RH both resulted in
<br />an unacceptable appearance (Table
<br />2).
<br />Accurate test. The results of this
<br />evaluation indicated that the gel-time
<br />test was the only powder test method
<br />that provided speedy and accurate
<br />information relating to the condition
<br />of an FBE powder.
<br />It is somewhat refreshing to note
<br />that, in these days of high technology,
<br />the findings of such simple tests as gel
<br />time or appearance panels can in fact
<br />detect problems with aged powders,
<br />while technically powerful tools such
<br />as the DSC could not accurately pre-
<br />dict or identify powder degradation.
<br />While the industry has widely ac-
<br />cepted the DSC as a most reliable tool
<br />for determining the extent of cure in
<br />an FBE coating, it is clearly not the
<br />panacea for detecting all FBE-powder
<br />characteristics and conditions.
<br />The results of this program and pre-
<br />vious research have clearly indicated
<br />that the results of the DSC can be
<br />significantly misleading if one consid-
<br />ers the OTg and AH results to be
<br />absolute reflections of the state or con-
<br />ditions of the coating or powder.1 6
<br />The DSC should only be utilized for
<br />tasks (such as cure determination) in
<br />which the method has not only been
<br />clearly defined, but also proven.
<br />References
<br />1. Temple, O.G., and Coulson, K.E.W , "Pipeline
<br />Coatings, Is It Really a Cover-up Story? - Part
<br />II," Paper 356, Corrosion 84, New Orleans.
<br />2. Mills, G., "The Interpretation of Differential
<br />Thermal Analysis Data for Fusion Bonded Epoxy
<br />Powder Coatings," Paper 112, Corrosion 83,
<br />Anaheim, Calif.
<br />3. Gray, C., Lunn, W.H., and McArdle, O., "Eval-
<br />uation of Epoxy Powder Coatings For Use on
<br />Steel Pipelines," Paper 118, Corrosion 83, Ana-
<br />heim, Calif.
<br />4. Temple, D.C., and Coulson, K.E.W., "The Use
<br />of Differential Scanning Calorimetry to Deter-
<br />mine Coating Cure," Materials Performance,
<br />Vol. 24, No. 11, p. 17, November 1985.
<br />5. Canadian Standards Association. "CANICSA-
<br />Z245.20-M86 External Fusion Bond Epoxy
<br />Coated Steel Pipe," August 1986.
<br />6. Dunn, I., sills, I.O., and Pleysier, R., "Moisture
<br />affects bonded epoxy line coating," OGI, Feb.
<br />24, 1986, pp. 63-77.
<br />USE OGJ REPRINTS
<br />Reprints of any article or advertise-
<br />ment appearing in Oil 8 Gas Journal may
<br />be purchased by contacting June So-
<br />zarth, Reprint Dept., PennWell Publish-
<br />ing Co., Box 1260, Tulsa, Ok. 74101, 1.
<br />800-331-4463 or 918.835.3161, ext.
<br />379. Minimum order: 100 black-and-
<br />white copies; 500 tour-color copies.
<br />Strain
<br />monitoring.
<br />averts line
<br />failure in
<br />Rockies
<br />Bruce Miller
<br />Western Gas Supply Co.
<br />Silverthorne, Colo.
<br />Michal Bukovansky
<br />Golder Associates
<br />Denver
<br />The case history of a landslide in the
<br />U.S. Rocky Mountains shows the po-
<br />tential for pipeline monitoring in geo-
<br />logically sensitive areas, those subject
<br />to landslides and subsidence, for ex-
<br />ample.
<br />A properly installed monitoring sys-
<br />tem monitored by the pipeline opera-
<br />tor, Western Gas Supply Co. (West
<br />Gas), Denver, provided an early
<br />warning of increasing line strains.
<br />Rugged topography. The Vail later-
<br />al supplies natural gas from West Gas'
<br />mainline in the vicinity of Climax,
<br />Colo., to the Vail valley, some 30
<br />miles north. The lateral was construct-
<br />ed in 1965.
<br />The pipeline is a• high-pressure, 6-
<br />in. line with 0.188 W.T., X42 grade.
<br />The pipeline alignment was devel-
<br />oped in exceptionally rugged topo-
<br />graphic conditions of the Rocky
<br />Mountains, with the line crossing the
<br />Re
<br />Continental Divide. Much of the
<br />alignment has been developed on
<br />steep and high slopes, mostly above
<br />the Eagle River. Rugged topographic
<br />conditions, high altitude, and locally
<br />unfavorable geologic conditions have
<br />contributed to occasional stability
<br />problems that caused a disruption of
<br />the line in 1984. Since then, other
<br />stability problems and landslides have
<br />been encountered along the line.
<br />These have required considerable
<br />mitigating efforts during the last few
<br />years. It is interesting to note that no
<br />stability problems were encountered
<br />along the lateral prior to 1984.
<br />The majority of the stability prob-
<br />lems are related to numerous land-
<br />slides that have been crossed by the
<br />alignment.
<br />Most of these landslides are old,
<br />having developed many years prior to
<br />construction of the line. Many of them
<br />are stable at present and do not en-
<br />danger the integrity of the line.
<br />Some of them have experienced
<br />significant deformations in the past.
<br />Some landslide. deformations appear
<br />to have been activated during the last
<br />few years, very probably because of
<br />exceptionally unfavorable climatic
<br />conditions of this period.
<br />The 1984 landslide occurred during
<br />late winter without warning. Although
<br />it disrupted the line, the gas supply
<br />was maintained.
<br />Following this event, West Gas de-
<br />cided systematically to evaluate stabil-
<br />ity conditions along the line and to
<br />mitigate the areas with the highest
<br />hazards. Golder Associates assisted
<br />Fig. 1
<br />Landslide 7 plan and pipeline deformation
<br />A
<br />11
<br />A'
<br />1. Boundary of landslide
<br />2. Probable location of original line installation
<br />0 50 100 200 3. Line location est. by Pipe locator
<br />4 Strain-gauge installation
<br />scale. ft 5. Line flexures caused by landslide
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