What is your approach to maintenance, repair and overhaul (MRO), and plant condition monitoring? Every type of plant is different, and their approach will also be dictated by the staff and engineers available, their budget, the age of the plant and the typical running cycle. This Industry Guide presents many different approaches and techniques, so that maybe there will be a few new ideas here, that might be useful on your plant.
If the plant is running well today, is it running the same as yesterday? How do you know? The answer is from some sort of measurement, and over recent years particularly, the sensors available to monitor plant operations have multiplied in number, and the software available for the analysis has increased in complexity and capability – and can be supplied remotely. These can now give even more information about operations, enabling optimisation of each stage of the process, and advance warning of possible equipment deterioration.
The main task for the plant manager now is to identify where in the plant he will allocate the available spend for monitoring to advise on wear and maintenance issues, and which plant operations could benefit from closer monitoring to find methods of improving performance – i.e. identify the critical areas. There will be specialists in, and equipment designed for every different type of plant – often from the suppliers – so the decision is now whether the monitoring can be via existing plant automation systems, or whether it has to be separate: and can these systems be managed by in-house staff, or does it need a specialist, or an external service operation, which might be Internet based – assuming the benefit justifies the cost?
The easy options
There are always lower cost easy options for specific tasks – and in general these have been taken up widely. For example it is not easy to detect a jammed or leaking steam trap on a plant walk-through. If you have an interested plant engineer and a wireless network across the plant, a dozen steam trap monitoring sensors can be rotated around different locations, and faulty traps identified in-house. A UK based power station has found this approach of significant benefit, using Emerson sensors on a WirelessHART network. Systems are also available on ISA100 networks, and from the major steam trap suppliers, like Spirax-Sarco and Armstrong.
Another area where advanced warning of wear problems is a benefit is in monitoring the bearings on heavy duty rotating machinery, like pumps, large fans and centrifuges. With a sensor on the outside of the bearing housing, any high vibration velocity can show the machine bearing is deteriorating: see ISO10816 for the trip levels. The bearing manufacturers themselves, such as SKF and Schaeffler, provide simple Go/No-go alarm systems, as well as multi-sensor monitoring for such things as big as wind turbines, backed by their bearing know-how. Some machines might deserve continuous monitoring, but there are wireless (self-powered) versions of these sensors that can be moved round the plant.
Developing the skill
Temperature measurement is classically a diagnostic that indicates something is unusual: “the engine is running hot”. While an engineer used to listen, feel, look for leaks, in modern plants the machinery is maybe not as easily accessible. Using an infrared camera or viewer at a distance can show up motors running hot compared to their neighbours, can show areas where pipe lagging is not working, hot steam drains, and even gas leaks from safety valves, joints etc. Suppliers such as Flir provide the equipment, but also offer a regular plant inspection service.
Advanced condition monitoring systems have been in use for over 50 years in nuclear plants and for gas turbines, using plant based specialist instrument engineers to analyse the data and trends (i.e. the plant history) to detect changes. Now the software and sensors available, plus the Internet, makes this analysis easier, and most equipment suppliers can monitor their kit remotely, as a service. Others (e.g. GE SmartSignal) offer to monitor your whole plant performance, whether an oil refinery or a power plant, from their 24-hour operating base, providing regular reports and warnings, and even a guarantee to “maximise productive output and lower operating costs”. An interesting Southampton University based development of similar sounding software is currently emerging, known as PrognoSYS, which will be supplied to equipment manufacturers to harness IoT sensors and techniques, to watch machine performance trends.
So, review the options, and choose your MRO system to suit your budget, your staff capabilities, and your critical plant areas.
Nick Denbow
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