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Pipeline Integrity Monitoring Approach
- Iain Weir-Jones, PhD, PEng President, Weir-Jones Engineering Consultants Ltd
Real-time data in monitoring the structural integrity of oil and gas pipelines aids pipeline operators for taking real, concrete steps to mitigate risks – real or perceived – associated with the use of pipelines to transport vital materials, and the risks that such infrastructure might suffer a failure leading to environmental damage or other consequences. In this article, the author illustrates the Real-time monitoring key advantages over previous-generation technologies in effectively mitigating the operational risks, data collection to improve the operator’s Mean-Time-To-Respond and reducing operating cost.

The last thing pipeline and resource companies need is an equipment failure that could cost millions of dollars in lost production, wreak havoc on the environment and result in skyrocketing legal fees. But as history has shown, such mishaps can happen, in particular when pipelines and related structures such as pump shacks and compressor stations are located in highly sensitive areas such as unstable hillsides, marshes, bogs, swamps, river crossings and steep grades.

Real-time monitoring is designed to overcome these and other design and construction challenges, and to keep pipelines, associated equipment and assets in running smoothly by monitoring their health in real-time.

Real-time monitoring provides clear and unassailable evidence that pipeline operators have taken real, concrete steps to mitigate risks – real or perceived – associated with the use of pipelines to transport vital materials, and the risks that such infrastructure might suffer a failure leading to environmental damage or other consequences.

Since such failures rarely happen instantaneously, vigilant monitoring is the only safeguard, allowing the operator to make informed decisions with the benefit of early awareness and operational response.

Real-time monitoring provides three key advantages over previous-generation technologies that manually monitor the structural integrity of oil and gas pipelines and enhances the environmental safety of pipeline operations. Operators are no longer required to walk the length of an instrumented section of pipe, or asset; they can simply be emailed ongoing reports as to the assets health, or monitor via a PC in the comfort of their office. This enables operators to access real-time data in their pipeline operations centre, providing superior visibility and enabling rapid response to changing conditions, which was not previously possible.

Real-Time Monitoring System
A real-time monitoring system is typically an aggregation and transmission node, buried in situ at a monitoring point on a pipeline, or asset that captures data from up to 16 discrete sensor inputs. These sensors can include strain gauges, piezometers, inclinometers, displacement transducers or other sensors with analog/digital outputs. Multiple nodes are connected in series to provide protection over long lengths of pipeline or throughout a site where a number of high value concern areas needs to be monitored on an ongoing basis.

Typically, the sensors are interrogated periodically and their average outputs are stored as a single sample. Therefore, local variance from one reading to another cannot disproportionately skew the results observed by monitoring personnel, and the incidence of false positives or false negatives is greatly reduced.

Under normal circumstances, a channel is sampled at a rate of 2000 sps and the sampling duration is defined by the operator at the time of commissioning. Currently, a sampling duration of 125 msec is used, which allows the averaging of 250 readings.

A node is assigned a unique address and communicates to a head end unit (HEU) over a dedicated cable that provides both power and data signals. The node may be deployed at spacings between 5 or 500 metres of pipeline, or on foundations, rotating equipment, power generators and so forth. Higher spacing densities on pipelines will typically be adopted when assessing the behaviour of over or underbends, or where other structural features are present such as tie downs or expansion structures.

Conversely, long, near horizontal sections of pipe, may see a significant reduction in real-time-monitoring node density unless geotechnical risks such as liquefaction sensitive soils due to seismic loading are deemed to exist.

Monitoring nodes are connected via a passive serial connection to the main backbone cable, which is protected from vandalism or environmental damage because it is attached to, and buried with the pipe, either secured directly or contained within protective conduit.

Advances in Real-Time Monitoring
There are three primary benefits to real-time monitoring as compared to legacy pipeline monitoring systems using intermittent manual readings. All of these benefits can be realised using a completely non-intrusive methodology that can be located in hostile or inaccessible areas, underwater or through any other type of terrain.

• Mitigating Operational Risk: Once the normal procedures are established and in use by the pipeline operator, it is possible to initiate internal service level commitments, and build business controls that ensure ownership and accountability for this performance is clearly assigned. It ultimately becomes possible for the operator to demonstrate how the total exposure to risk (from physical failure, operator negligence, or force majeure) can be greatly reduced because the data collection by a Real-Time Monitoring System and the operational processes in place to support that data collection all collaborate to improve the operator’s Mean-Time-To-Respond.

• Real-Time Pipeline Monitoring: Legacy systems do not provide live visibility into pipeline integrity monitoring because the data collection processes are manual and inconsistently periodic. Therefore the risk of failing to detect changes in critical parameters in a timely manner is significant. In fact, early warning signs from sensors for geomechanical changes in the surrounding ground, for example, might never be noticed.

The essential value of real-time monitoring is therefore one of enabling the pipeline operator to implement a standard library of response processes when certain conditions are detected on one or more nodes. This can be achieved without any increase in staffing because the data presentation software provides the triage and discrimination functions necessary to highlight only when anomalous conditions are present. Therefore, the operator may be confident that data is being archived in a non-repudiable repository, and that whatever trigger conditions are desired can be unequivocally associated with an operational response procedure. These, in turn, can be measured for performance against target as part of standard operational audits.

• Reduced Operating Costs: Traditional monitoring nodes required an above-ground access point for the operator to use in connecting to the sensors and retrieve any accumulated data. These points were subject to numerous physical and environmental risks such as vandalism, weather exposure, or displacement due to seismic or relative movement between the surficial material surrounding the pipe and the pipe itself.

Real-time monitoring of critical infrastructure is no longer a nice luxury; it is essential not only for operational performance management, but also as part of the broader Corporate Social Responsibility strategy, with all its attendant public relations implications.