David Walker, director for Wireless Solutions, Middle East & Africa, Emerson Process Management explains that the evolution of wireless technology has seen it come of age as a mature technology, and one which can make you upstream operations run more smoothly.
If you don’t have wireless as part of your automation toolbox, then you’re behind the curve. I’m living proof of that.
I started my process control career back in the UK in the early 1990s. I was given a company car and a territory, but there were no practical cell phones back then, nor any WiFi or hot spots. I bought myself a road atlas to find my way around my new territory.
I didn’t have a Blackberry or a laptop. All my calls were noted down in a filing system. I didn’t even have a car phone – I had to keep my eyes open for a phone box so at lunchtime I could call the office and check for messages.
It was a real pain when a customer cancelled a meeting; I had to stand in the phone box and call other customers to see if they could see me.
Today, we all have wireless at home and in the car, and my life is much simpler. Technology has moved quickly and now there are multiple wireless technologies that we all use and probably take for granted, with cell phones the best example.
Wireless is increasingly easy to use, with push button setup of home wireless networks taken for granted.
Wireless has similarly worked its way into the process industries, due to a host of improvements driven by customer needs. But like my road atlas and phone boxes, wireless started out as a clumsy, expensive and difficult solution.
My first wireless project was back in 1999 when a customer wanted to put in a control system bridge to a remote location; the best technology at the time was a microwave link. The entire system was expensive and relatively complex, and all the wireless technology was proprietary.
Wireless networks had been around for about 10 years, but there were many competing protocols. Because vendors’ network and protocols were different, equipment from one supplier wouldn’t work with systems from another.
So, acquiring data from wireless sensors and instruments often meant using gateways, converters and special software to deal with the various protocols involved.
Today, however, it’s all different. Thanks to WirelessHART, a widely recognized worldwide standard, wireless in a process industry application is as easy to use as a Bluetooth connection to a cell phone.
WirelessHART was developed specifically to meet the requirements of the process industries. The HART Communication Foundation (HCF) worked with end-users in the process industries—who demanded coexistence, reliability, long battery life, security and multi-vendor interoperability.
The HCF also worked with process equipment vendors, and with experts on radio frequency and wireless communications, and came up with a scheme that satisfied all parties.
WirelessHART was ratified in September 2007 by HCF, and approved by IEC in 2010 as the first international wireless standard. Since then, the technology has taken off worldwide.
For example, Emerson Process Management announced in October 2011 that its customers had achieved 580 million total hours of wireless operation across 6,100 networks, all based on WirelessHART.
And Emerson is just one of many suppliers supporting WirelessHART and building products in compliance with the standard. There are about 17 vendors making WirelessHART products today, including most of the major process control equipment manufacturers, with more coming onboard each month.
IMS Research reports that worldwide shipments of industrial products that are wireless-enabled are set to grow from an estimated 1.2 million in 2009 to more than 3 million in 2015, an average annual growth rate of 18 percent. With numbers like these, wireless has certainly gone mainstream.
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Working with Wireless
One reason that WirelessHART has been adopted so quickly by the process industries is because it’s so easy to use. Instrument engineers know how difficult it is to hard-wire a field instrument, such as a flowmeter or a level transmitter, back to an automation or information system.
First, precautions have to be taken to ensure the wiring is safe, and meets all hazardous-area requirements. Next, hard-wired cables have to be routed through cable trays and I/O concentrators, and through marshaling cabinets or junction boxes, all at great expense in labor and equipment.
In spite of extensive design and layout efforts, the end result is still often a “rat’s nest” of wiring that’s difficult to maintain. None of this is needed with wireless.
With wireless, the savings in wiring and related components is obvious. With fewer components such as cabinets and conduit systems, there’s less need for ancillary equipment such as space heaters and cabinet cooling systems. This means savings in time and money, as well as a smaller footprint and less weight, and of course fewer wires.
In certain space- and weight-constrained applications such as offshore platforms, wireless can be particularly advantageous.
Probably the most obvious advantage of wireless sensors is that their cost of installation is far less than a hard-wired system. But another advantage is ease of installation.
WirelessHART is a mesh network, where wireless devices talk to each other at a range up to 100 meters, and autonomously form wireless communications paths back to a local gateway (see Figure 1).
For example, to commission an installation of wireless sensors, a user starts commissioning the devices closest to the gateway. As these nearby devices power up, they become aware of their neighbors and make automatic connections.
As more devices are added, they self-organize into mesh networks. A user doesn’t have to tell the devices which other devices or gateways they should look for as these tasks are handled by the gateway. In Emerson’s case, this gateway contains a network manager.
Once the mesh has formed, any changes to the mesh—such as by a permanent or temporary obstacle—will be managed by the devices themselves by finding an alternative path to the gateway.
The redundant data paths inherent to a mesh network eliminate single points of failure. Actual installations consistently demonstrate greater than 99 percent data reliability. WirelessHART uses a unique full mesh-topology as many as seven hops deep, providing an important advantage: WirelessHART doesn’t need a costly infrastructure of multiple backbone routers installed throughout the plant within range of every wireless device.
Running costly hazardous area power supplies to backbone routers is therefore also not required.
Overall, a wireless system is much simpler to modify than its wired counterpart. If a device changes or moves, it’s not necessary to make wiring changes. If more devices are needed, another gateway can be added which will handle 100 more devices.
WirelessHART has tools available to help plan and monitor the networks, analogous to Foundation Fieldbus and other hard-wired sensor and instrument networks. As with these hard-wired networks, the required tasks are similar: follow best practices, plan the network and it will work without problems, guaranteed.
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Built-in Security
A major concern for many is security. Everyone has heard of cell phone hackers, intrusions into poorly protected home wireless network, and other problems involved with commercial wireless systems. Those problems don’t exist with WirelessHART because of its built-in security.
WirelessHART communications use a security protocol with 128-bit encryption and 24 hex join codes, making hacking very difficult. Another important security feature is that there is no IP address in the wireless devices, making it very hard for any would-be hacker to make initial penetration.
WirelessHART security measures include encryption, authentication, verification, key rotation and sequence number. WirelessHART security cannot be turned off, ensuring these security measures are constantly active.
Communications to the host control system from the wireless gateway is typically over Modbus RS485 or Ethernet. Almost all control and automation systems support Modbus, so there’s no excuse for not getting started with wireless.
Device Diagnostics
Users can get a wealth of diagnostic information from a wireless sensor or instrument, similar to that available from a hard-wired fieldbus device or a conventional HART-based instrument.
Many users installed HART-based instruments mainly because of the extensive diagnostic information available, but estimates are that only 10% of the installations actually use this information to the full extent.
Many companies instead limit their use to handheld devices that operators use to manually calibrate and check field instruments during commissioning and calibration.
Part of the problem with wired HART devices is they have to communicate over a relatively slow 4-20 mA connection, and special software is involved. Not so with WirelessHART—instead, the full range of HART diagnostics is available via the high speed wireless connection, and asset management software can extract the HART information.
Because WirelessHART is the next revision of the HART standard, it’s familiar to the user. They don’t need to buy new tools or take new training programs to understand WirelessHART.
Even older, wired instruments can be added to the system with a WirelessHART adapter. This capability opens up a whole new area for maintenance and diagnostics. For example, many plants have valves that every so often have to be pulled from the line for an overhaul.
By adding a wireless adapter to a HART-based valve actuator, users can get access to all the details needed to make an informed and proactive maintenance decision, instead of running to failure or performing unneeded maintenance. The same general proactive maintenance principles apply to flowmeters and related instruments.
Wireless solves problems that were too difficult or too costly to approach before with hard-wired solutions. For example, an Emerson customer in the Middle East has remote pumps, and they wanted to measure pump performance to make informed maintenance decisions (see Image 1 above).
Previously, they used a portable vibration analyzer unit. The maintenance people would go to the pumps, collect data and make a decision. The interesting thing about this application is that the pumps are in the middle of the desert. It’s up to an eight-hour drive to get to the site.
Often, trips would be made and a pump wouldn’t be running, so data couldn’t be collected. It was too expensive to install an online vibration monitoring system, so each pump ran until failure.
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Emerson worked with the customer to mount accelerometers on the pump casing with the transmitter located close by, communicating wirelessly to the WirelessHART gateway, which connects to the main control system over a wide area network.
The vibration process measurement information is communicated through the customer’s automation system to their enterprise historian. The historian then makes this information available to the reliability engineer at his desk through the corporate Intranet.
Now, the customer’s reliability engineer could see on the historian if there was a problem with a pump. If so, the engineer could phone the operations team, and they could go out and correct the problem. An interesting note is that the reliability engineer sits up to 350km away from the pumps.
Difficult to traverse distances lend themselves well to wireless applications. Sometimes it is prohibitively costly to install instrumentation and wire it back to a central location, and wireless can often solve the problem.
At a wellhead in the Middle East, one of our customers has about 2,500 wireless devices across multiple gateways collecting well data, something that was difficult and slow to deliver with a hard-wired system.
Temperature devices show our customer if product from each well is flowing. Previously, they had teams driving around the field in trucks and putting their hands on pipes to determine if the well was producing.
The customer told Emerson that his pay back period was nearly instantaneous, given the tremendous savings in maintenance and operating costs. Water wells are a similar application in the Middle East, and in many parts of Africa.
Additional wireless Applications
Having a wireless infrastructure in a plant allows users to cover additional applications such as rotary kilns, safety relief valves and steam traps.
Acoustic transmitters allow monitoring of steam traps and pressure relief valves, and they can easily be added to the wireless network. In the U.S., it’s estimated that there’s a $10,424 annual fuel loss per leaking steam trap. With wireless, it’s easy to monitor critical steam traps for leaks, and start saving money immediately.
Wireless cameras can be used for monitoring people, hazardous locations or site security, asset tracking and safety mustering. Now sites have a way of keep track of employees and visitors. It has also made the application of safety mustering easier and verifiable.
These applications typically use WiFi, not WirelessHART, and need exciters on choke points, doorways, and an entry to a building. Personnel tracking applications require a plant to have WiFi coverage for tracking RFID tags, often accomplished by aerial mounting of wireless transmitters and receivers.
Finally, wireless can be used for backhaul networks. There may be remote locations or obstacles such as mountains or roads that prevent getting remote information back to central monitoring points via wired networks.
Modern WiFi or WiMax wireless networks make it feasible to bring this information to where it’s needed, and to do this much easier than in the days of proprietary and expensive wireless networks.
