Safety Study

Supervisory Control and Data Acquisition (SCADA) in Liquid Pipelines

NTSB Number SS-05/02
NTIS Number PB2005-917005

Executive Summary

SCADA - Supervisory Control and Data Acquisition—systems are a type of industrial control system used to collect data and exercise control from a remote location. In the pipeline industry, SCADA systems are used to collect data from pipeline sensors in real time and display these data to humans (controllers) who monitor the data from remote sites. Controllers, in turn, can use the SCADA system to input commands that remotely operate pipeline control equipment, such as valves and pumps. SCADA systems are widely in use in oil, gas, electricity, and municipal water systems.

For this study, the National Transportation Safety Board examined the role of SCADA systems in the 13 hazardous liquid line accidents that the Safety Board investigated from April 1992 to October 2004. In ten of these accidents, some aspect of the SCADA system contributed to the severity of the accident. The principal issue in the SCADA-related accidents investigated by the Board was the delay between a controller's recognizing a leak and beginning efforts to reduce the effect of the leak. SCADA factors identified in these accidents include alarms, display formats, the accuracy of SCADA screens, the controller's ability to accurately evaluate SCADA data during abnormal operating conditions, the appropriateness of controller actions, the ability of the controller and the supervisor to make appropriate decisions, and the effectiveness of training in preparing controllers to interpret the SCADA system and react to abnormal conditions.

This study was designed to examine how pipeline companies use SCADA systems to monitor and record operating data and to evaluate the role of SCADA systems in leak detection. The number of hazardous liquid accidents investigated by the Safety Board in which leaks went undetected after indications of a leak on the SCADA interface was the impetus for this study. The study describes SCADA systems being used at pipeline companies that transport hazardous liquids and examines the extent to which the SCADA system design helps or hinders controllers in detecting leaks and acting to limit the amount of product released.

The Safety Board developed a survey to obtain data about the liquid pipeline industry's use of SCADA systems with input from industry. The survey covered basic information about the pipeline company and its SCADA system. In total, 87 percent of the control centers targeted by the survey responded. In addition to obtaining survey data, the Board visited 12 pipeline companies that had operating SCADA systems. The Board interviewed personnel who developed and used SCADA systems for the pipeline company. A total of 69 persons were interviewed. Interviewed personnel included controllers, supervisors, and SCADA systems managers. In addition, the Board examined the SCADA system and reviewed its design and development with a company representative who was responsible for the system's operation and maintenance. The Board also reviewed SCADA-related job aids that controllers used during the course of their work. Based on information from previous accidents investigated by the Board, survey results, and site visit results, the Safety Board's review of SCADA systems in the hazardous liquid pipeline industry uncovered five areas for potential improvement:

As a result of this study, the Safety Board issued five recommendations to the Pipeline and Hazardous Materials Safety Administration.