Page:NTSB - Railroad Accident Report - Derailment on May 25, 1989.djvu/27

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a hole into the pipeline, and withdraw product at that location. According to the Calnev maintenance superintendent, they were aware, by referring to company pipeline maps, that a check valve was installed in the pipeline immediately north (upstream) of the derailment site at pipeline milepost (MP) 6.9[1] (figure 5). Calnev officials stated that they believed that removal of the product from the pipeline at the location south of Highland Avenue would cause the check valve to seat (close) thereby isolating the pipeline north of the check valve from the pipeline in the derailment area. Further removal of product from the pipeline would then reduce the pressure in the pipeline in the derailment area. After excavating at the location south of Highland Avenue, Calnev officials determined that the location was not suitable for tapping the pipe because the pipe was buried in the ground at a depth of 14 feet and was inside a steel casing. Calnev officials then moved their activities to the Colton terminal where a 2-inch fitting with a 1¼-inch opening was installed on the 14 inch pipeline, and they subsequently began withdrawing product from the pipeline at that location.

According to Calnev’s maintenance superintendent, after about 120 barrels of product were removed from the pipeline (and loaded into a vacuum truck), the pressure was reduced about 60 psig at the Colton pump station (MP 0.0) and at Cajon Pass (MP 25.7).[2] Because the pipeline pressure had been reduced by an equal amount on both sides of the check valve at MP 6.9, Calnev personnel determined that they had not been successful in seating (closing) the check valve at that location and, consequently, had not been successful in isolating the pipeline in the area of the derailment. The equal reduction in pressure also indicated that the check valves at MP 14.9 and MP 19.2 had not seated.

Believing that they had been unable to withdraw product at a rate adequate to induce product backflow sufficient to fully seat the check valves, Calnev personnel installed a threaded fitting through the new opening and connected it with high pressure hoses in an attempt to withdraw product at a faster rate. According to Calnev personnel, a second vacuum truck load of product (120 barrels) was then withdrawn and comparable results were observed—an equal reduction in pressure on both sides of the check valve at MP 6.9. As a result, Calnev knew that the check valve at MP 6.9 was not closing. Calnev’s maintenance superintendent stated that he then recommended that additional pressure reduction could be achieved by closing the block valve at the Cajon Pass pump station. After the block valve was closed, a third vacuum truck load of product (120 barrels) was withdrawn from the pipeline and a 200-psig reduction in pressure was achieved. Once again, however, the pressure readings at the Cajon station and at the Colton station

  1. Milepost numbers for the pipeline do not correlate with the milepost numbers for the railroad.
  2. The static pressure in the pipeline varies with the elevation of the line. Therefore, the pressure reduction, rather than the pressure reading, was the critical observation at the two locations.