DUAL COATING SYSTEM USED ON CALIFORNIA REFINERY LINE

Dec. 31, 1990
Mobil Oil Inc. selected a new pipeline combination-coating system for pipelines near its Torrance, Calif., refinery. The system was selected to address the severe conditions of high operating temperatures within the pipeline and severe terrain and weather conditions affecting the pipe exterior. Mobil Oil produces crude oil from a large oil field in the San Joaquin Valley, Kern County, about 150 miles north of Los Angeles. One of the company's major crude-oil pipelines crosses desert,

Mobil Oil Inc. selected a new pipeline combination-coating system for pipelines near its Torrance, Calif., refinery.

The system was selected to address the severe conditions of high operating temperatures within the pipeline and severe terrain and weather conditions affecting the pipe exterior.

SEVERE CONDITIONS

Mobil Oil produces crude oil from a large oil field in the San Joaquin Valley, Kern County, about 150 miles north of Los Angeles. One of the company's major crude-oil pipelines crosses desert, foothills, and urban development from the Kern County fields to the Torrance refinery south of Los Angeles.

This heavy San Joaquin Valley crude requires heating before it will flow. Operating temperatures of about 85 C. (180 F.) make the pipeline vulnerable to corrosion.

Mobil selected the DuVal coating system after a 2-year test program conducted for Mobil at an independent testing laboratory in Houston.

The system was developed by Du Pont Canada Inc. and Valspar Inc., West Hill, Ont.

TWO-PART PROCESS

The DuVal coating system employs a unique, two-part process. Unlike conventional pipe coating technologies, the two coatings are tailored to each other in the patented process which forms a chemical bond between layers.

The bond thus enhances the pipe protection both mechanically and electrically.

The inner layer is fusion-bonded epoxy (developed by Valspar) which provides a strong bond to steel but whose performance in weathering and water absorption is below standard. In addition, its maximum operating temperature is 180 F. at normal coating thicknesses in a wet environment (210 F. or more in dry conditions).

The exterior layer is a Du Pont polyolefin, either polyethylene or polypropylene, in the form of a Fusabond coating. These are much better in keeping out moisture and can be tailored to match precise operating requirements.

Due to the operating temperatures of the Mobil pipeline, polypropylene is employed.

Energy Coatings Co., Fontana, Calif., undertook the main coating assignment. Shop bends for the pipeline were handled by Commercial Coating Services Inc. (CCSI), Conroe, Tex.

The two-layer DuVal coating requires two separate coating lines operating in tandem to meet the tight processing requirements because the polypropylene top layer must be applied immediately after the fusion-bonded epoxy.

Joint coating was accomplished in the field by CCSI's Bakersfield, Calif., operation after the joints had been girth welded, X-rayed, and inspected. Pipe laying contractor was Murphy Bros. Inc., Bakersfield.

Mobil has installed more than 1 mile of 16-in. pipe with the DuVal system in the Torrance refinery. Following an environmental impact study, more pipe will be installed.

According to Du Pont Canada, the DuVal system is also planned for use in an even more hostile environment (higher temperatures) in Nigeria.

Work is scheduled to begin later this year.

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