WPL`s 12 years experience in hydrotesting answers questions
- Williams Pipe Line Co., Tulsa, OK (United States)
Recently issued DOT rules requiring pressure testing of older hazardous liquid pipe lines have raised questions in the minds of many operators. Williams Pipe Line (WPL) has been testing its mainline system since 1982 and the results of testing about 6,600 mi over a 12-year period might answer some of those questions. WPL began hydrostatic testing its system by evaluating two sections of a critical line. Knowledge gained encouraged the company to enlarge the program`s scope. In the next five years, six in-service ERW seam failures occurred, one resulting in significant damage. Two lines involved had two seam failures with within a two-year period. All seam failures recorded on the WPL system were analyzed in 1987 revealing that certain lines exhibited higher structural failure rates than others. The longitudinal weld seam in the ERW pipe was made with a low-frequency weld process that left sections of the weld not completely fused. Many of these nonwelded areas eventually developed into failures after years in operation. Based on WPL`s seam-failure analysis, an agreement was made with DOT in 1987 to reduce operating pressure by 20% on lines with higher seam failure rates, establishing a 1.25 safety factor. Since the analysis also revealed several lines installed before DOT regulations required hydrostatic testing, the company decided to establish a prioritization program to test all pipe lines in its system that had not been tested since 1982. Objective was to eliminate in-service seam failures and ensure integrity of the system.
- OSTI ID:
- 170117
- Journal Information:
- Pipe Line and Gas Industry, Vol. 78, Issue 6; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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