Gas pipelines mounted on bridges and other above-ground supports are subject to many types of potential damage. A monitoring system warns of safety incidents.

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Sung-Kyung Hong from the R&D Institute, Korea Gas Corporation, writes of his firsthand experience designing and implementing a monitoring system for exposed gas pipelines using accelerometers to detect damage.

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“We designed the safety management system to monitor the structural safety of exposed gas pipelines. With these exposed pipelines, the city cannot always stop gas flow immediately, which can lead to extensive large-scale damage if an accident occurs. In addition, many of the exposed gas pipelines are attached to bridges. Even though the bridges were initially constructed properly, many factors, including secular changes, fewer support members to hook up the pipeline, problems related to the bridge structure, and intentional damage to the pipeline make it difficult to implement safety management systems during bridge development. To ensure complete safety, we needed a highly reliable, 24-hour monitoring system that was not subject to downtime, even in environments with poor conditions.

“Drilling construction, also known as ‘other construction,’ occurs in areas where pipelines are buried below ground level of the gas pipeline view, such as subway and ground lamp construction. When this type of construction begins, we implement suspension protection to guard the exposed pipelines. Because exposed pipelines increase the risk of accidents, we set up on-site management or shorten the inspection period to reinforce safety management by performing more frequent inspections.

“We used CompactRIO hardware from National Instruments to install our highly reliable system in environments with poor conditions, such as construction sites or bridges, to continuously monitor and secure the safety of exposed gas pipelines. We also developed this system to be free from erroneous operations, even when the warning alarm was triggered.

“We developed the system using the NI cRIO-9004 embedded real-time controller and the NI cRIO-9103 four-slot, 3M gate reconfigurable embedded chassis. We used a microelectromechanical-based accelerometer to measure the exposed pipeline oscillation. This accelerometer was less expensive than an integrated electronic piezoelectric (IEPE) accelerometer because its signal was less diminished over the line length, and it used regular cabling instead of coaxial. Therefore, we used the NI 9201 C Series analog input module instead of the NI 9233 C Series four-channel dynamic signal acquisition module.

“With the NI 9237 bridge and strain measurement module, we measured the stress change of the exposed pipelines. Because we needed the strain gage to measure the length of the pipeline, we installed the half bridge to decrease the noise impact over the line length.

“We also installed equipment to generate the short message service (SMS) using code division multiple access (CDMA) so that safety management field workers could receive warning alarms at any position via cell phone. We installed the CDMA equipment as the serial interface and programmed the system to sound a warning alarm when anything regarding oscillation or strain exceeded the levels initially established.

“To ensure we achieved our goal of to secure 24-hour pipeline monitoring, we needed dependable hardware that would not experience downtime so that the system could operate properly if accidents occurred, even in environments with poor conditions. We chose to use CompactRIO as the system hardware because it was dependable and durable, which influenced how we applied the sensors.”

Edited by Peter Welander, pwelander(at)cfemedia.com

Control Engineering