CALIFORNIA REPLACEMENT EMPLOYS SPECIAL COATING, CONSTRUCTION PRACTICES

Warren R. True
Pipeline/Gas Processing Editor

Mobil Oil Corp.'s West Coast Pipe Lines has been flowing heavy crude oil through its $90 million M-70 replacement pipeline since last spring.

Mobil installed a single 16-in. line specially coated for heated crude oil in place of a line parts of which were more than half a century old and which changed diameter several times.

The line's coating required almost 15 years of research and development, the pipeline was laid in narrower than usual trenches under and along busy streets of several Southern California urban areas, and the project survived a determined legal challenge.

1916 VINTAGE

The so-called M-70 line, a 92-mile segment of the 170-mile San Joaquin Valley (SJV) pipeline system, runs from Mobil's Lebec station in Kern County, crosses the Tejon Pass and Angeles National Forest into the San Fernando Valley, crosses the Santa Monica Mountains, and moves through West Los Angeles to its terminus at Mobil's Torrance, Calif., refinery.

The line passes through Los Angeles County and the cities of Los Angeles, Culver City, Inglewood, Hawthorne, and Torrance (Fig. 1).

Before replacement, the M-70 line could carry as much as 63,500 b/d annually.

The project replaced all 92 miles of a line that had originally been constructed in 1916 and had been totally replaced in small segments. The result by 1991 was a mix of diameters and coatings. The segments ranged in age from 2 to 55 years old.

So much short replacement of line pipe and coating had taken place over the years that the 92-mile segment changed diameters 42 times, varying between 10, 12, and 16-in. pipe (Table 1).

Approximately 27% of the line replaced was 12-in. x 0.250-in. W.T. API 5L-X52 ERW line pipe coated with a high-temperature bitumastic enamel with fiber glass wrap laid in the late 1960s and early 1970s.

Also replaced was the approximately 50% that had consisted of 10-in. x 0.250-in. W.T. API 5L-X52 ERW line pipe coated with mastic and extruded polypropylene laid in the mid-1970s.

SPECIAL COATING

The oil that flows in the line is heated to 160 F. and moved by four pumping and heating stations at Lebec, Newhall, Saticoy, and Slauson.

Each station has two direct-fired heaters. Additionally, the Lebec station has four 900-hp electrically driven centrifugal pumping units, the Newhall and Saticoy stations have two such units, and the Slauson station has two 450-hp units.

Individual heaters range from 7.7 MMBTU/hr at Lebec and Slauson to 9.4 MMBTU/hr at Newhall station.

The new 16-in. pipe (mostly 0.344-in. W.T. API 5L-X52 ERW) has DuVal coating consisting of 22 mils of fusion bonded epoxy (FBE) with a 22-mil topcoat of a chemically modified polypropylene (CMPP; OGJ, Dec. 14, 1992, p. 42).

The coating, a response to the high temperature of the oil, is the product of almost 15 years of research in a joint effort by Mobil Pipe Line Co., Valspar Inc. (Canada), and DuPont Canada Inc.

The trick was to modify the polypropylene so that it would bond to the FBE.

The coating was applied by Energy Coatings Co., Houston, at its Fontana, Calif., plant. Richard Norsworthy and J.A. Nunn of Mobil Pipe Line Co., Dallas, described the coating process to the 1992 API Pipeline Conference.

The procedure begins with inspection of the stored pipe for damage and contaminants--oil, grease, salt, so forth.

After a preheat of 150-180 F., dual blasting machines blast the pipe to a "near white" surface with a 1-3 mil anchor pattern.

The pipe is then inspected for burrs and other damage.

A phosphoric acid-based treatment (which should result in a pH of 1 for at least 20 sec) and a clean-water rinse are used to remove contaminants that may remain after blasting.

Norsworthy and Nunn said this step is best accomplished between the two blast machines, if possible.

A thin layer of chromate is then applied to protect the pipe further and strengthen the FBE bond to the steel.

After surface preparation, the pipe is heated to a temperature of 450-463 F. with heat induction or gas-fired ovens.

Once proper temperature has been established, the pipe will travel through the FBE spray booth.

Approximately 22 mils of FBE are applied. Before the extended-gel FBE is gelled (within approximately 9-12 sec), the 22 miles of CMPP is side extruded or flocked on in powder form.

Norsworthy and Nunn said side extrusion is the method being used by most coating companies.

The bond between the FBE and CMPP may be inadequate if applied outside these limits, they said. The thickness of each of the two components can be varied to suit expected operating temperature.

The coating is then quenched with water to remove as much heat as possible, yet allow proper cure of the coating. Additional internal quenching of the steel may be added to make the CMPP become harder for proper handling.

After quenching, the coating is visually and electrically inspected for holidays and other damage. The holidays found are usually from burrs on the pipe, mechanical damage, or contamination in the coating.

The coating thickness is checked and the pipe labeled with pertinent information. Separation ropes are placed on the pipe. The ends are buffed back to the correct cutback for welding and field-joint applications.

After bevel protectors are installed, the pipe is stored until transportation to the job site. All coated pipe is handled with padded equipment or proper hooks or slings to prevent damage.

STREET WORK

Installation consisted of two major spreads: one for north Los Angeles County and one for south Los Angeles County.

ARB Inc., Bakersfield, Calif., was primary contractor in the north; Hood Corp., Whittier, Calif., in the south.

Both ran simultaneously.

Approximately 56 miles of the new line were laid in and following city streets in trenches that were narrower and deeper than conventional trenches (Fig. 2).

To avoid disruptions to traffic and more than necessary repair to city streets, Mobil limited the width of its trenches to 24-30 in. In rural areas of the project, trench width was up to 48 in.

To ensure line integrity and safety, Mobil buried the new line to 48 in.

More than 50 miles of the line was routed onto new right-of-way, much of it within urban areas. Mobil deviated in some instances to reduce the impact of construction on traffic, elsewhere to avoid newly resurfaced streets, and still elsewhere to avoid such environmentally sensitive areas as parks and the Sepulveda Dam recreation areas.

In addition to the line pipe installation, Mobil modified the four pump stations converting existing pumping units from series to parallel operation to increase pumping capacity and efficiencies.

At Lebec station, an additional electrically driven pumping unit was added to three existing units as well as their being converted from series to parallel operations.

Capacity of the line following line pipe installation and pumping station modifications is now 95,000 b/d.

LEGAL SKIRMISHES

As with most pipeline construction these days, the M-70 replacement project had its adversaries.

In May 1991, after the City of Los Angeles had approved the project in April, the project's environmental impact report was challenged in a suit against the city.

During the summer of 1991, the city issued the necessary construction permits, however.

So that in September, when a judge in the Superior Court of California, County of Los Angeles, denied the basis for the suit, construction began in the city and in north Los Angeles County.

In November, however, the opposing group filed an appeal of that decision which was denied in December 1992 by the Court of Appeal of the State of California.

In the meantime, the cities of Hawthorne (on Mar. 23, 1992), Torrance (on May 19), Inglewood (on June 30), and Culver City (on Oct. 26) all approved the project and issued pipeline franchise ordinances to Mobil Oil Corp. allowing construction to proceed within their jurisdictions.

By Mar. 1, 1993, approximately 90 miles of the 92-mile project was installed. The remaining 2 miles in Culver City were finished by late March and the project construction was completed in early April.

The new line was hydrostatically tested on Apr. 1, tied into the longer SJV system on Apr. 5, and became fully operational on Apr. 9.