Underwater pipelines continue to prove its usefulness and necessity to so many countries and the world at large due to the fact that these pipelines are not only mediums used to transfer water, petroleum and natural but also connectors of power plants, oil and gas wells, refineries and even shipping ports between countries. Some may even call these pipelines an irreplaceable asset to the world’s economic stability and growth. Hence, subsea pipeline monitoring and protection are of great importance to the world. One of the major means of monitoring the different types of pipelines is sensor networks. Sensor networks are a group of tiny devices powered by batteries that monitor and record environmental conditions in any number of environments from a hospital lab to out in the sea. They carry out pipeline communication and transmit the collected data for analysis through the internet, a specialized industrial network or an enterprise WAN or LAN.
Here we will discuss three sensor networks; their reliability, network connectivity, continuity of power supply for the network, physical network security, problems and proposed solutions.
SENSOR NETWORK ARCHITECTURE
Underwater Wired Sensor Networks: This is the traditional means of pipeline communication and subsea monitoring. They are easily installed and not only do they act as a means of communication, they are also used to transmit electricity -generated from solar energy, pipeline flow energy or other external energy- to all parts of the pipeline. They are connected using either copper or fiber optic network cables and connected to regular sensors that measure flow rate, motion, pressure, temperature, vibration, sound, and other environmental attributes. However, these underwater wired sensor networks have a number of challenging factors;
1. Pipeline communication is completely or partially ruined if any damage to any part of the wires occurs.
2. The network can easily be disabled by cutting a network wire.
Irrespective of its easy mode of monitoring subsea pipelines, its challenges present it as a total unreliable system. Using multiple networks with one as primary and others as a backup is thus a suitable but “ticking bomb” solution as it just lays the foundation for a much larger loss.
Underwater Acoustic Wireless Sensor Networks: Wireless networks solve some of the problems of wired networks as they have no wires that are at risk of being damaged or disabled and ruins communication as a ripple effect. Acoustic wireless sensor nodes are installed in the pipelines; with each node having a limited transmission capacity. They transmit sensed data through multi-hop communication. Underwater acoustic wireless sensor networks have a few problems of their own:
1. Limited bandwidth among nodes.
2. Due to the unreliable nature of the underwater channels, acoustic signals are sometimes delayed.
3. Connectivity loss and error rates are higher with underwater acoustic nodes.
4. Battery is not renewed or replaced as easily as it is consumed.
One way to boost the reliability of these sensors is; instead of having nodes far apart and causing them to burn more power, sensor networks should be divided and spread in multiple but closely related parts.
Integrated Wired/Acoustic Wireless Sensor Networks: As a solution to the network connectivity, continued power supply and physical security problems of the wired and wireless sensors, the integrated wired/acoustic wireless sensor network architecture for underwater communication is proposed. It consists of several point-to-point segments linked to the system nodes which are in turn connected to an acoustic transceiver and a wired network interface. These nodes are comprised of processing, monitoring, and storage units and are connected through wireless acoustics and wired links which recharges the nodes.
Demand for energy, petroleum, natural gas, water, water resources and water facilities continues to rise every day and as such, subsea pipeline monitoring and pipeline communication must be a major concern to us all.