Shipboard Machine Monitoring for Predictive MaintenanceFebruary 1, 2006 By: Tom Kevan Sensors
In 2004, BP became aware of a wireless networking technology called motes, 2 X 2 in. devices that combine a processor, solid-state memory, a radio, and an I/O board that can interface with sensors. These motes could potentially be used to tie sensors into a wireless network, which then could pass data to back-end systems. But most of the motes were going to academics, laboratories, and industrial manufacturers that were still evaluating the technology. No one was actually creating commercial products in those days.
"Once we found this technology, we had to determine if it worked in our industrial environments," says Harry Cassar, BP's technology director, digital and communications technology. "The motes that we saw were delicate, almost bare printed circuit boards. We wondered if they could be put into environments with high metal content, such as a refinery, where there are also high levels of vibration and extreme temperatures. Could they be packaged in a way that would allow them to work in these environments? The only way to find that out was to try it. And that is how the Loch Rannoch project was born."
The Loch Rannoch project began with the testing and evaluation of mote technology, but BP didn't stop there. The project was actually a multiphase effort that went on to develop a commercial wireless sensor networking system that could be used in BP's industrial production facilities around the world. Each phase encountered its own hurdles and produced its own solutions.
BP's first hurdle was to decide where to conduct its project. Most of its operations required the use of intrinsically safe equipment. To test the wireless networking technology, which did not have that certification, the company looked for an environment that had some of the harsh conditions found in its facilities but that did not require intrinsically safe equipment. The company settled on the Loch Rannoch, a 1000 ft., 132,000 ton oil tanker that shuttles oil from a storage vessel called the Schiehallion to an oil-processing terminal at Sullom Voe, in the Shetland Islands.
The ship had a higher metal content than a refinery, making it a tougher environment from an RF point of view. In addition, the ship had compartments that could be shut off by watertight doors, so there were steel barriers between one compartment and the next. There was also significant vibration from the main engines, generators, and thrusters, and the temperature inside the engine room was between 80°F and 100°F.
BP's chief technology office worked with BP shipping to decide on the focus of its pilot project. "If we were going to do a test on the Loch Rannoch, we suggested that perhaps it would be good to choose an application that would have some real benefit rather than just doing a test to see if the motes could talk to each other," says Cassar. "And BP shipping said that they would like to collect vibration data from a set of rotating machines in the engine room."
BP's project developed a new predictive maintenance system capable of monitoring critical rotating machinery, such as the pumps and motors in the Loch Rannoch's starboard engine room, using vibration data to evaluate operating conditions and wireless communications to send alerts when wear and tear was detected.
"Vibration data can help you understand how a machine is wearing and help predict when you should do maintenance," says Cassar. "Condition monitoring can tell you when a shaft is out of true or when a machine is out of balance. It helps you move from time-based maintenance—stripping the machine down, say, every 500 hours—to doing maintenance when it is required."
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