On July 30, 2004, a natural gas pipeline operating at a pressure of 70 bar ruptured. The accident occurred at Ghislenghien industrial park, near Ath, Belgium about 30 miles southwest of Brussels, Belgium. Twenty-four people died as a result of the explosion and subsequent fire (mostly firefighters and the police), and 120-plus were hospitalized, most with severe burns.
The pipeline was one of a pair that ran from Zeebrugge, on the North Sea coast to the French border. At the location of the rupture it passed under a factory car park where construction work by a third party had been going on. Third-party damage to underground pipelines continues to be a source of danger to workers and members of the public. The financial and reputational damage caused to utility companies is significant.
For major accident hazard pipelines, as defined by the Pipelines Safety Regulations 1996, such as those containing high-pressure natural gas, ethylene, oil or gasoline, the consequences of a rupture can be devastating for people and the environment. Third-party damage has the potential to result in the most severe pipeline failures (full bore pipeline ruptures, for example), which dominate the risk to the public.
The damage to the Ghislenghien pipeline occurred during the final stages of a car park construction project. The pipeline operation had been notified of the work and one of its representatives had regularly visited the site. The damage likely occurred between visits as a mechanical soil stabilizer was driven over or near to the pipeline. This resulted in several gouges in the steel wall of the pipeline. After the car park was completed, the gas pressure was increased and the pipeline ruptured, resulting in an explosion and fire.
Although Ghislenghien may be atypical of most third-party damage incidents in the U.K., which are often a result of roadside utilities work, it is still important to manage such undertakings carefully. National Grid has guidance for its own high-pressure network titled, “Safe Working in the Vicinity of National Grid High Pressure Gas Pipelines and Associated Installations – Requirements for Third Parties”
Its key points in maintaining project safety are:
• Contact the pipeline operator to obtain formal consent;
• Consider the safety requirements;
• Inform the pipeline operator prior to carrying out work and arrange for them to locate the pipeline;
• Observe the pipeline operator’s restrictions on the allowed proximity of mechanical excavators and other power tools and the measures to protect the pipeline from construction vehicles when carrying out the work, and
• Ensure everyone involved understands the importance of avoiding pipeline damage and of reporting any near misses, especially if it involves surface or coating damage to the pipeline.
Statistics from the European Gas Pipeline Incident Data Group show that its members operate more than 135,000 km of natural gas transmission pipelines, representing about 50% of the total length in Europe. In the UK, National Grid operates about 7,600 km of transmission pipeline transporting high-pressure gas.
While this network is an efficient and low-risk means to move large quantities of gas around the country, there is considerable potential for third-party damage to occur if excavation works adjacent to pipelines are not adequately controlled. This is particularly true where the pipelines enter urban areas.
National Grid’s high-pressure pipelines are generally laid across country within an easement (way leave in Scotland) agreed to by the landowner or within the highway. Normal agricultural activities are not usually considered likely to affect the integrity of the pipeline; however, in most other cases no work is undertaken in the vicinity of a pipeline without the formal written consent of the operator.
Third parties may excavate with powered mechanical equipment no closer than 3 meters from the National Grid pipeline and with handheld power tools no closer than 1.5 meters from the pipeline. All other excavations must be carried out by hand. National Grid may supervise some third-party work, however, for work near a pipeline an exclusion zone is usually set up with a National Grid representative who visits the site regularly to ensure that the barriers remain in position.
Recognizing that between visits damage to the barriers may occur, National Grid worked with GL Noble Denton to develop a monitoring system for use between visits by the company representative. An initial market review showed that a low-cost solution could be developed with the use of mobile phone technology. Two off-the-shelf camera systems were selected for trial. These were mounted into pipeline aerial marker posts since these are both portable and relatively discreet (although not covert). The two systems had different capabilities and allowed an assessment of the benefits of particular features to be made.
Images from the camera systems could be readily obtained, either by a text message request or by a video call direct from a suitable mobile phone. One system had the ability to pan and tilt under remote control from the mobile phone, while the other was fitted with a fish-eye lens to increase the field of view.
Although the range and resolution of the images was good, the appearance on a small mobile phone screen was unsatisfactory, but not unusable. However, it was found that the battery life, even with additional alkaline battery packs, was inadequate, particularly during cold times of the year. The trial did, however, result in one camera being selected for further development, in collaboration with the original UK equipment manufacturer.
In the latest phase of the development, a robust mounting system was designed and manufactured to enable the production of an initial batch of cameras with fixed fish-eye lenses for National Grid. The battery life has been improved with the use of an external Li-ion pack, which enables it to last for up to two months unattended in the field (a model that includes a photovoltaic panel to recharge the battery is also in development).
In order to allow a suite of cameras to be managed from a single workstation, a secure website platform has been developed with software to allow images to be requested, viewed and downloaded to a personal computer. The initial batch of cameras are in the field for further evaluation but expectations remain high that these will be adopted throughout the network for temporary monitoring purposes.
The camera system has been developed as part of National Grid’s Innovation Funding Incentive program, an initiative which has been running since 2007. The primary aim of the incentive is to encourage network operators to innovate and to provide funding for projects primarily focused on the technical development of the network assets in order to deliver value (e.g., safety, efficiency, reliability and environmental benefits) to consumers.
The development of this low-cost camera system has the potential to improve the monitoring of the network during third-party work and potentially to reduce the cost and environmental impact (miles driven) of National Grid’s activities in this area. The camera could be readily incorporated into different enclosures, including different types of marker post and has potential for other applications in the future.