Counter intuitive16 January 2013
Production managers quite rightly insist on high equipment reliability and availability. But while many believe this rules out wireless plant and factory communications, Brian Tinham finds that concerns are largely unfounded
Wireless instrumentation and control equipment has, for several years, been promising industry everything from cost savings on automation system extensions to hitherto infeasible product quality and efficiency gains. Salespeople given to hyperbole have even suggested that safety and reliability might be improved. So why have so few factories and process plants adopted the technology?
In part, the reason is nothing more sinister than a reluctance to break with accepted custom and practice. Hence, few have been taken the plunge, so there's little experience and you're into catch 22. But it's also about confidence in the robustness of wireless, as opposed to physically wired plant comms. And, while there is little justification for that stance – certainly, if wireless is being considered only for monitoring – caution is understandable.
Nevertheless, as Honeywell Process Solutions wireless business manager Diederik Mols asserts, for many plants the pressure is on to improve operational metrics. And that's a real challenge. "With hard-wired technology, there's a limit to what you can do, unless you're prepared to spend a lot of money," he says. "Today, in the office we're used to wireless solutions, with instant access to real-time data, and we need that in the industrial environment."
Mols speaks of an unnamed onshore plant, which installed vibration monitoring on critical remote sea water cooling pumps but, because wiring costs were prohibitive, didn't connect it to the plant management system. "Because readings were taken every two weeks, a pump imbalance was picked up too late, which led to the equipment failing beyond repair. The replacement took months to arrive and, as a result of the downtime, they lost 20% of their capacity – which was huge money."
His point: wireless leads to a very different cost-benefit analysis for real-time data collection capable of preventing such catastrophic failures. Indeed, Mols and others claim a 50-70% cost saving, compared with wired installations (not only in terms of the physical infrastructure and engineering work, but also drawings, documentation, etc), and even greater time savings – making hitherto unjustifiable plant installations entirely viable.
But wireless is not just for such extreme projects. Consider the growing availability of wireless-enabled sensors, process transmitters and, of course, PDAs and smartphones, all capable of transforming the availability and cost of operational and diagnostic information. Field Advisor, developed by Shell and available through Honeywell, is one example of the latter. Shell, which deployed the system on around 25 sites, reckons it contributed to reducing plant downtime on average by 50% and, in some cases, 80%. How? Because there's no longer a delay between plant readings and trends being observed, and maintenance and process optimisation engineers getting that information and acting on it.
Plainly, there are significant benefits, so how reliable are the technologies? Emerson Process Management talks about two tiers. On the one hand, there are mains-powered IEEE 802.11 WiFi standard networks (developed with Cisco), for mid-range plant and factory communications, pulling data from cameras to asset tracking systems. On the other, there are low-power field networks (ISA 100.11a and IEC 65291 WirelessHART (highway addressable remote transducer)), designed for instrument communications – and almost exclusively monitoring, not control, because of their still relatively slow (circa one second) update rates.
Both the latter are self-organising, self-healing, frequency-hopping 'mesh' networks, running at 2.4GHz. Treve Tagg, Emerson's European instrument business manager, insists that reliability is excellent. "Around 1,500 sites in the chemical, and offshore oil and gas sectors are now running WirelessHART networks and in excess of 75% of these are not proving the technology, but working installations."
Beyond these, there are also proprietary wireless solutions – such as that developed by IMC Group, which operates at 433MHz. This is claimed by sales director Derek Richardson to provide for an order of magnitude better long-distance propagation, including through buildings and equipment. "Our systems are used primarily for temperature and humidity monitoring, for example in museums and public buildings. But we have also done a lot of river level monitoring, bringing real-time information back to a gateway, with GSM alarming to control centres."
German EnOcean also offers wireless sensors – in its case, harvesting power from local sources, such as motion, light or temperature differential. Its chosen frequency bands are 868MHz and 315MHz, and it boasts ultra-short 1msec deterministic transmission bursts.
Given the range of horses for the different courses, it's hard to imagine there isn't something there to suit most requirements. It may seem counter intuitive, but wireless may well improve plant and factory reliability, as well as product quality, rather than compromise it.
Emerson Process Management
Hanwell Solutions Ltd
Honeywell Process Solutions
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