Born again20 March 2014

Instrumentation continues to evolve, offering better ways to monitor and control plant operations – and hence improve product quality and yield.

It's easy to imagine that, with control systems development lagging only a little behind the pace of computing, surely instrumentation must be the poor relation? To an extent, it is. Look at Yokogawa's latest Mirror Plant model-based simulation system, for example. Not only does it provide control room training to help maintain the competence of operators on high-risk plant such as offshore platforms, but it is also now capable of fast-forwarding to predict process upsets and validate alternative control strategies.

Jointly developed with Yokogawa subsidiary Omega Simulation, Mirror Plant is being made available as part of the former's VigilantPlant Services, designed to support safe, stable and efficient operations for oil and gas, petrochemical and similar plants. And it is clever: systems product manager Mike Keightley describes it as operating synchronously with main plant control systems, its high-fidelity dynamic models accurately visualising the internal process state to make its predictions.

Following field testing at one of Mitsui Chemicals' plants, where the system cut its teeth optimising distillation tower operations, Mirror Plant has now been implemented in the North Sea and at South Hook LNG, in Wales. "They've pushed it to its limits," says Keightley. "They used it for control system engineering and commissioning, as well as plant simulation and as a test platform linked with the live system to predict the plant's future path."

It's a similar story with condition monitoring systems. Statoil, for example, has awarded a $2.7m contract to Emerson for integrated plant and machine performance monitoring for the Gina Krog oil and gas platform in the Norwegian North Sea. Based on Emerson's DeltaV control system, this is to enable Statoil personnel onshore to monitor the new platform's critical pumps, compressors and associated equipment to maximise efficiency and identify evolving problems before they affect production.

This system is to include Emerson's CSI 6500 Machinery Health Monitor and AMS Suite predictive maintenance software. It also includes a wireless communication infrastructure, based on IEC 62591 (WirelessHART), capable of capturing data from platform equipment not currently connected to the system at much lower cost than hard-wired alternatives. Statoil expects the system to help maximise production by minimising downtime while also reducing maintenance costs.

But there's more to instrumentation than meets the eye. Level and thickness sensors, for example, can harness anything from radar to microwave, ultrasonics, admittance, capacitance, magnetism, hydrostatics and mechanical arrangements, depending on the application, its value and criticality, the environment, and accuracy and repeatability required.

Look at the radar instruments recently designed with funding from the EPSRC (Engineering and Physical Sciences Research Council) for researchers in Antarctica to measure the health of one of the ice shelves. "The millimetre accuracy of this system is made possible by a phase-sensitive processing technique we developed," explains Paul Brennan, professor of microwave electronics at University College London. "We have also redesigned the electronics to minimise noise so that the units are highly sensitive at low power."

Each radar unit draws just 5W and runs off a 6V battery that can last a whole year, topped up by a small wind generator or solar cells during summer. The units also have MIMO (multiple input multiple output) antenna arrays that allow the researchers to construct 3D images of the ice.

Then again, SKF recently launched a laser vibrometer for maintenance engineers concerned with condition monitoring on applications such as fans, electric motors and pumps. Dubbed MSL-7000, this digital device covers acoustic measurements from 0.2 Hz (for slow rotations) up to 22 kHz, and Werner Palmetshofer, general manager at distributor Steyr-Werner's condition monitoring centre, says it's easy to integrate into test set-ups and control systems.

How about Emerson's next generation tuning fork viscosity meters? These build on its Micro Motion 7827 and 7829 direct insertion viscosity and density meters, designed for demanding applications where accuracy and speed of response are critical.

Brian Tinham

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