Bridging the gap between safety and security with fibre optic sensing
11 March 2014
For many years within industry, matters of safety and security were handled very differently and often managed and financed by separate teams. We are now starting to see these two critical aspects become more closely aligned, partly because of new technologies. One such technology is Distributed Acoustic Sensing. Jerry Worsley, Global Sales Director of OptaSense Ltd, discusses this application and how it is causing safety and security to align.
Fibre optic sensing has been deployed in various safety and security applications for a number of years, but it is only recently that a single technology has been used to bridge the gap between both.
Distributed Temperature Sensing is commonly used in safety applications such as fire detection within tunnels or conveyor belts within road and rail applications. The principle of the technology is to determine absolute temperatures or the ‘Delta T’ at any given point along the length of the asset to signify a hotspot caused by fire. Similarly, this can be applied to power cable monitoring. This allows operators to manage the load according to the temperatures experienced along high voltage cables and therefore prevent any failures that could cause cable failure and the associated safety issues and power outages. Likewise optical fibre systems have been deployed as perimeter security systems. As well as providing a data path for access control and CCTV cameras the fibre was fixed directly to the fence and used as an energy sensor to detect vibration caused by climbing or cutting.
The introduction of Distributed Acoustic Sensing has allowed experts to provide a never-before-seen level of intelligence to a completely passive sensing component such as an optical fibre. It is this inert nature of the fibre cable that makes it so advantageous in a volatile environment. As many of the cable structures are made from silica, aramid yarns and Halogen-free materials, they are completely unreceptive and can therefore be installed where other sensors or electrical cables cannot. Distributed Acoustic Sensing, or DAS, was originally developed within the telecoms industry to locate fibre optic cables that carried no metallic components and were therefore impossible to trace. Engineers would know the approximate location of the cable and then “stamp” in the vicinity whilst a colleague would “listen” to the system and confirm when they were approaching the cable. An accurate location could then be determined which would allow for additional surveillance devices to be installed in close proximity. The technology has come a long way since then.
What is OptaSense?
The Optasense system converts a standard single-mode fibre optic cable (often the same cable used for SCADA communications) into an array of virtual microphones. A highly stable laser is pulsed at 10,000 times a second and the Rayleigh backscatter is monitored for signs of “excitement” within the fibre molecules. This is called Coherent Optical Time Domain Reflectometry (C-OTDR). This reaction can then be monitored by an operator. But it should be noted that OptaSense can monitor up to 50km of fibre from a single unit location. This equates to 4,000 individual channels being heard, which is impossible for any operator to monitor as a raw set of signals. OptaSense creates acoustic fingerprints in order for the system to autonomously monitor and detect events along the length of an asset and send alerts of specific events. This is especially important when connecting multiple devices together thus monitoring thousands of kilometres.
Oil & Gas
In 2008, OptaSense installed the first Distributed Acoustic Sensor systems to detect Third Party Interference within the pipeline right of way. Now DAS is not only being used to protect pipelines from damage accidentally or maliciously, but is also being used as a condition monitoring tool, allowing the operator to control and schedule its in-line inspection tools. Additionally, the technology can act an online leak detection system for guaranteed safe operation.
OptaSense can replace the need for in-well logging tools
Using algorithms developed from 40 years of sonar deployment, OptaSense used the knowledge gained within the defence sector to detect, locate and classify intrusion events such as personnel, vehicles, manual and mechanical digging. The same techniques are now being deployed to locate and track the speed of pipeline inspection gauges and determine the presence of leaks.
The OptaSense Four Dimensional Leak Detection is extremely robust as it not only monitors for sound of the leak, but also the effects of the surrounding environment, including:
1. Acoustic anomalies
2. Negative pressure waves
3. Temperature variations (DTGS)
4. Environmental strains
Having four modes of leak detection ensures that leaks as small as 0.1% can be detected within a gas, liquid or multiphase form.
OptaSense was originally designed as a security product, and it is therefore this application that is most mature and widely adopted around the world. To date, it has been deployed in regions including South America, North and West Africa, the Middle East, Europe and Asia. Our experience has taught us that a majority of threats are not malicious. The image of an organised syndicate installing hot taps and drawing down product at will is one that has been widely used in the past. However, the common threat to operational security and safety is that of the local farmer digging a bore hole for irrigation or construction worker digging foundations with a back hoe.
OptaSense is currently deployed on over 11,000km of pipeline, and features include the provision of real information the client needs to operate a safe and secure network. This also includes safe valve operation and condition monitoring of remote equipment such as motors or air conditioning units.
OptaSense Web Services displaying a history of activities over the length of the asset
Fibres are also being deployed downhole with the well completion. This removes the requirement to install sensors such as PLT Gauges or Geophones within the high pressure environment of the well bore. A single 9-micron fibre strand can monitor processes such as Vertical Seismic Profiling (VSP), Hydraulic Frac Profiling (Fracking) and Flow Assurance in a permanently installed, safe low-pressure environment.
Cyber security is also a major concern to operators around the world. The threat of a plant SCADA system being breached and configured to create an unsafe environment is very real. Touch points along an asset such as pipeline Block Valve Stations are vulnerable to attack. OptaSense protects those as well, as the fibre optic artery that connects back to the main Control Room.
We all know that copper theft is an issue on the European rail networks. The loss of signalling cable with a relatively insignificant financial value has a huge safety implication that affects the entire rail network. This in turn causes delays and massive fines for the network providers. Traditional technologies include Policing and CCTV - the issue with this is how many and where? Other deterrents include doping the cables with a fingerprint that can be detected at the scrap metal dealers. This may make the disposal more difficult but it doesn’t prevent the initial theft.
OptaSense has been deployed on various rail networks to help prevent copper theft through identifying where and when intrusions take place. In addition to copper theft, The system also provides a safe environment by detecting other interruptions - whether malicious or innocent, human or animal. This not only helps provide a safe rail network from third party interference, but can also be used to monitor any maintenance personnel by tracking their location and movement.
The ability to listen to a rail network also allows the client to monitor track and rolling stock in real-time. Train speed and location can be identified to the nearest 10 metres allowing headways between trains to be closely monitored and controlled. Anomalies on track and rolling stock such as wheel flats, rock fall and landslides can also be recognised and alerted.
Likewise traffic flow on roads can be monitored using the existing communications fibre infrastructure. Current solutions including induction loops are expensive to install and maintain as they involve road closures. Using the existing fibre infrastructure installed at the side of the road, OptaSense can monitor traffic density and speed as well as detecting stopping vehicles on motorways and alert Highways Agencies of any such events.
Although it can be utilised for a number of safety applications, security is still a primary use of OptaSense. Whether installed on a perimeter fence or along the border of a country. it can detect where, when and what attempted incursions take place. Key to the solution is the ability to remove false alarms through its filtering system and to integrate with third party equipment such as CCTV, Alarms or even Unmanned Air Vehicles (UAVs). Again, the fact that it deploys a very low cost fibre cable as the sensing medium mean this technology can be deployed where others may not be suitable such as Nuclear facilities or in other similar harsh environments.
An important part of the mix is not only knowing how to react to incidents, but also how to present the information to the client’s management team. The OptaSense online tool ensures that management personnel can easily view real-time or historical data to help develop their operational and security processes in the future. Types, locations and levels of threats can be addressed. This helps to develop trends over the length of the asset. It also quickly diagnoses where any improvements may need to be made or what effects operational changes may have caused. Multiple assets can be viewed from multiple locations and reports generated at a click of the button. These have been developed with the clients to ensure the required information is captured and presented.
Safe and secure
Multi-purpose, multi-benefit solutions such as OptaSense allow single systems to be applicable in both the security and safety space. This is affecting the way operators are specifying and funding their solutions, bringing telecoms, security, SCADA and safety systems closer together. The key aspects are that all the information is available to those who need it, systems are secure and data is reliable.
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