It is ubiquitous in our private lives, but to date the adoption of wireless technology within a plant's monitoring and control infrastructure has been sporadic and isolated at best. Yet, when it was first proposed as an alternative to hard wired systems, many believed that it would transform plant and factories as it has since done to both home and office.
In the early days of industrial wireless, influential analyst Harry Forbes, of ARC Advisory Group, was prompted to say: "Wireless is the most fundamental improvement in process automation in decades." Although it certainly has not yet had the transformative impact that Forbes predicted, nevertheless it is apparent that it has huge potential.
Slow beginnings
When specifying monitoring and control system devices and communications types, plant engineers need to examine the options around attributes such as functionality, but also security, reliability, robustness and real-time performance. With an existing plant having a legacy hard-wired monitoring and control infrastructure, there is plainly little technical or financial advantage in installing a plant-wide wireless system. That said, wireless communications can certainly offer localised benefits that augment the existing infrastructure (see later), while on new plants there could be a strong case for going at least partially wireless. Either way, even in cases where wireless has been adopted, to date its primary function has been for monitoring, with control remaining very much in the domain of wired Industrial Ethernet (or earlier plant networks).
"In the early years there was a lot of resistance to industrial wireless," agrees Diederik Mols, business manager, industrial wireless solutions at Honeywell Process Solutions. "But over time [engineers] have found it does work and so the question has largely changed to 'How can it be applied to our facility?' What we typically see is that, once the vision is there or the initial investment has been made into a wireless infrastructure, after a year or so there are four or five more plant applications being considered." It is much like the growth of smartphone use, he muses. "Over time we all see additional applications being thought of and then asked for." And on plants and factories, those applications may not only be efficiency- and process improvement- related, but also around personnel health and safety requirements.
Future growth
"We look at wireless in three ways – sensing, mobility and backhaul, which is more the infrastructure," explains Forbes. "You'll hear a million buzzwords about wireless sensor networks, but [monitoring and control] is a very distinct application and one that is very challenging." According to Forbes, mobility is currently the major driver for wireless adoption – both in terms of the process industry and factory automation, but also in externally in general. "Backhaul is the hidden part – we've had that for years in SCADA [supervisory control and data acquisition] applications. Essentially, it's just a segment of telecoms, but it's an important part of bringing the sensing [plant data] and applications to the network infrastructure."
Putting meat on those bones, Forbes suggests that, in terms of sensing, the process industries are way ahead of discrete manufacturing with operational applications. "The reason for that concerns the characteristics of the automation itself," he says. A lot of factory applications would be of interest, but they can't tolerate the latency." Hence, in part, the failure of the much-predicted 'pervasive sensing' – a future of low-cost sensors installed everywhere.
But another segment of the overall wireless market that Forbes believes is forcing adoption concerns smart devices, and in particular sensors and instruments for tracking people and hazards. "Mobility is the really big application and it's using a different technology," he says. "In the case of mobility it's really the flip side of wireless, as it's in discrete industries, not process, where you see it more widely deployed. At somewhere like GM, for example, the wireless LAN is absolutely critical to the whole operation. Anything that moves around and is not wired-in is connected to that wireless LAN – materials handling and vehicles, both automatically and manually guided, are very critical."
Martin Walder, UK manager for industries at Rockwell Automation, is in broad agreement. "Wireless is still very much in its early days. It is being used most at the mobile monitoring level. There have been more and more [wireless] sensors, process instruments and I/O blocks coming into the market over the past couple of years. And although the uptake, like a lot of these things, is steady to start with, there is no question that it is going to ramp up. On all the longer-term schemes that we are looking at we are considering Wi Fi options."
Stranded assets
Why? Because one of the most important benefits of a wireless network is its sheer flexibility. With the cost, size and power requirements of processing power and transmitters falling fast, an ever greater number of devices have intelligence and the ability to communicate built in. This allows recently installed equipment, physically remote or isolated equipment, and rotating or mobile plant – such as cranes – to be wirelessly connected through a node on an Industrial Ethernet network. And that makes hitherto unavailable information available to plant operators, maintenance engineers, schedulers and planners.
One area that has seen rapid adoption is dispersed wellheads in the oil and gas industry. "With wells dotted around and several kilometres between them, no power and certainly no wired communications, wireless is the perfect solution," Walder explains. "We've tended to put three or four wireless process instruments at a wellhead where the customer can then monitor and potentially also control the flow of the well via an RTU [remote terminal unit (RTU]." And such an approach can have clear advantages for any plant and equipment at some remove from existing networks and cabling – 'stranded' in the parlance of this industry – for which there is a business or process improvement case for real-time (or near real time) monitoring and/or control.
Boon for mobility
Two of the latest buzzwords within industry – the 'industrial internet of things' (IIoT) and the 'connected enterprise', where entire industrial environments have transparency from top to bottom – are being driven in part by wireless technology. At the plant information 'layer', managers would traditionally be sitting in a control room looking at an HMI [human machine interface] plant mimic, with alarms, trends, etc. Now the client software for those systems can reside on tablets with built in Wi-Fi.
"Managers or engineers with Wi-Fi can be wandering around plants seeing exactly what the control room personnel see while actually watching the process in front of them. They can see alarms and see exactly what is happening on plant in real time," Walder explains. "Likewise, people in a remote control room on the other side of the world can have exactly the same visibility, and with negligible propagation delays."
Wireless will grow more quickly
Industrial wireless can and will grow and at a much faster rate than presently because the prospect of adding wireless devices to process and factory automation infrastructures is compelling – both at an operational and business level. Its adoption will be helped by the emergence of IIoT and the demand for a more connected enterprise. Wireless technology will also allow the explosion of sensors and instruments at the device and equipment levels (pervasive sensing) necessary to deliver the data to applications, systems and users. With such persuasive benefits, obstacles such as competing industrial wireless standards at the sensor and device level will become less daunting.
Communications protocol
When it comes to communications standard there are two main competitors. First is WirelessHART, an open source standard, now available from FieldComm Group, the organisation formed earlier this year by the merging of Fieldbus Foundation and the Hart Communication Foundation. Then there is ISA100 Wireless, an open, wireless network protocol that, with its universal IPv6 addressability, makes it compatible with the Internet of Things.
"The standards battle is a pain point for end users – Emerson and Endress+Hauser are a big backer of WirelessHART while Honeywell and Yokogawa are on board with ISA100," confirms Forbes. "A lot of process manufacturing firms have equipment from both camps and they are not pleased with the situation of two different standards. Nevertheless that doesn't keep them from deploying."
As the WirelessHART and ISA100.11a standards continue to gain footholds, most process wireless transmitter users will move away from any remaining legacy proprietary solutions. "Concurrent with this shift, a migration away from standalone point-to-point installations will occur in favour of mesh-based, inherently redundant device level solutions that interface to a Wi-Fi-based plant or facility backbone," adds Forbes.
With more than 40 million [wired] HART devices installed worldwide, WirelessHART is in a strong position. "WirelessHART is a wireless mesh network communications protocol ideally suited to process automation applications," states Chuck Micallef, marketing consultant with FieldComm Group. "It adds wireless capabilities to the HART protocol while maintaining compatibility with existing HART devices, commands and tools."
Each network type includes three main elements. First, there are the physical wireless field devices monitoring and/or controlling plant or factory equipment. Second, gateways enable communication between these devices and host applications connected to a high-speed (often existing) plant communications network. Finally network manager firmware is responsible for configuring the network, scheduling communications between devices, managing message routes and monitoring network health. Logically, the network manager can be integrated into the gateway, host application or process automation controller.
"The network uses IEEE 802.15.4 compatible radio transmitters operating in the 2.4GHz industrial, scientific and medical band," explains Micallef. "The transmitters employ direct-sequence spread spectrum technology and channel-hopping for communication security and reliability, as well as TDMA [time division multiple access] synchronised, latency-controlled communications between devices on the network."
Each device in a mesh network can serve as a router for messages from other devices – meaning they don't have to communicate directly to a gateway, but can forward messages to the next closest device. This extends the range of the network and provides redundant communication routes to increase reliability. It is the network manager's job to determine current routes, based on latency, efficiency and reliability. And, to ensure the redundant routes remain open and unobstructed, messages continuously alternate between redundant paths.
"Consequently, like the Internet, if a message is unable to reach its destination by one path, it is automatically re-routed to follow a known good, redundant path, with no loss of data," explains Micallef. "The mesh design also makes adding or moving devices easy. As long as a device is within range of others in the network, it can communicate."