NEW LEAK-DETECTION SYSTEM PASSES TRIALS, HEADS FOR FIRST INSTALLATION

A unique detection system for tracing leaks from oil and gas pipelines has been successfully field tested by Shell Chemicals U.K. Ltd. at its Stanlow petrochemical complex in northwest England. First-ever installation will take place later this year on a 138-mile NGL pipeline in Scotland. The statistical pipeline leak detection (SPLD) system spots leaks by using computer calculations of statistical probability. It can detect leaks with an unusual degree of speed and accuracy, says Shell, as

March 29, 1993

3 min read

A unique detection system for tracing leaks from oil and gas pipelines has been successfully field tested by Shell Chemicals U.K. Ltd. at its Stanlow petrochemical complex in northwest England.

First-ever installation will take place later this year on a 138-mile NGL pipeline in Scotland.

The statistical pipeline leak detection (SPLD) system spots leaks by using computer calculations of statistical probability. It can detect leaks with an unusual degree of speed and accuracy, says Shell, as well as locate where a leak is occurring.

But SPLD can be installed at a fraction of the cost of conventional systems and run on a standard personal computer, according to Shell.

SYSTEM BRAIN

The "brain" of the system is a specially programmed computer package of statistical data, unique to the pipeline it is monitoring. It constantly analyzes flow rates and pressures, making hundreds of high-speed calculations per minute to check for unusual trends.

The sensitivity of the system enables it to trace leaks as small as 0.5% of the total flow through the pipeline, says Shell, and its speed means it can trace significant leaks within minutes. SPLD was first conceived in 1988 by Jun Zhang at Shell Research in Amsterdam and brought to Stanlow in 1990 for further development with the Stanlow pipeline group.

Initial field trials were conducted in 1990 on pipelines between Stanlow and the Shell chemical plant at Carrington near Manchester. Shell installed SPLD on four pipelines with a total length of 150 km (94 miles), carrying ethylene and propylene from Stanlow to Carrington.

John Millett, Shell's pipeline manager at Stanlow, says that SPLD's credibility is greatly enhanced by its very low rate of false alarms, even when set to operate at peak sensitivity.

In May 1992, SPLD was successfully demonstrated to the U.K. Pipeline Inspectorate of the Health & Safety Executive.

FIRST INSTALLATION

Shell says that SPLD has proven fast and reliable. Other, more conventional leak-detection systems are limited by their reliance on the accuracy of flowmeters and instrumentation.

But SPLD goes beyond relying totally on instrument accuracy and can therefore detect much smaller leaks.

Shell U.K. Exploration & Production (Shell Expro), the North Sea exploration and production division of Shell U.K., plans to install it later this year on the main 138-mile pipeline carrying North Sea NGL from the company's gas terminal at St. Fergus near Aberdeen to its Fife NGL processing plant at Mossmorran (OGJ, Mar. 8, p. 37).

Shell Expro is also considering the new system for some of its major offshore pipelines.

Shell has granted a license to LICconsult Stockton-On-Tees in Cleveland, U.K., to market the system worldwide. It will be marketed under the name Licstat.