Look around you. You probably have operating parameters you’d like to measure and track to satisfy the requirements of regulators, especially with FDA getting serious about implementing parts of the Food Safety Modernization Act (FSMA). Electronic recordkeeping is a must if you’re required at a moment’s notice to verify temperatures at critical control points or the effectiveness of washdowns and CIP operations. Today, manual thermometer readings, clipboards and spreadsheets won’t cut it. Data acquisition/control systems and historians help you collect necessary data and provide the time stamps you need to show auditors and regulators your processes are under strict control.
You say there’s just one problem in implementing a new data acquisition system—where to run the wires. Of course, a greenfield plant doesn’t have this problem because it’s been designed to accommodate sensor and control wiring—often in the form of digital sensor/control networks. But, where a wire can’t be easily routed in an existing plant, chances are, there may be some wireless sensors or controllers to make the radio connection back to the data acquisition/collection/control system.

Where wires can’t go

“Temperature measurements are one of the most common applications for wireless, and in many cases, the reason is because it’s simply too costly or difficult to run cable and conduit to the locations you are trying to measure,” says Steven Toteda, Cooper Bussmann vice president and general manager, wireless business unit.
Examples include temperature gradients across heat exchangers, or cryogenic freezers that must maintain critical ultra-low temperature without any interruption, adds Toteda. Temperatures of liquids and solids being stored in locations like outdoor silos or tank cars are also good applications for wireless systems. 
Cold chain applications are well suited to wireless applications, according to Frank Uhlemann, Eckelmann division manager. Eckelmann’s compact wireless sensor can be installed directly in cold rooms and warehouses. Depending on the installation, the sensors will measure the temperatures at intervals of five to 30 minutes at up to 100 control points and send them to a receiving module. The data can be transferred to any refrigeration control system or building management system, or reviewed directly through the web or on a PC. 
Omega Engineering customers use wireless products in key food and beverage applications, reports Ashish Desai, data acquisition group. “This includes temperature monitoring during food production, ambient room condition monitoring, packaging, distribution and storage. Omega temperature monitors are used during the fermentation, sterilization and pasteurization process in the beverage industry.”
Desai notes that his company’s wireless temperature and humidity sensors are also deployed in greenhouses and grain storage silos. A food equipment company in California is currently using the UWRTD-NB9W wireless sensor during the testing phase of its large mixing machines. A Michigan cereal-making company’s test lab uses a wireless system because Omega’s wireless receivers have analog outputs. A Nebraska pet food company found the same receivers very useful because of their multiple analog and alarm outputs. A Florida fishery uses the receivers for ease of integration into its PLC-based sorting operation. A New York meat processing company uses Omega’s penetration probes with its wireless transmitter to log historical data for quality control, which used to be handwritten on quality charts. 
“In many applications, wireless becomes a viable option when it comes to taking some cost out of the overall installation expense,” says Justin Shade, Phoenix Contact product marketing specialist, wireless. “When it comes to food and beverage, there are typically many obstructions to running wires that could cause the installation to take longer and require more material. Using a wireless system helps alleviate those issues and can create a more cost-effective installation that also cuts down on repairs.” Phoenix Contact offers a broad range of wireless options that work in extreme temperatures and survive washdown conditions. 
The specifications for the wireless transmitters that are part of the Emerson portfolio have the same environmental ratings as its wired transmitters, according to Bob Karschnia, vice president wireless, Emerson Process Management. “This means that the transmitters can withstand temperatures up to 85°C and 100 percent RH. They are also ingress rated to NEMA 4X/IP66 and, therefore, can withstand water washdowns.”
According to Michael Robinson, Endress+Hauser solutions business manager, E+H’s wireless products withstand the same temperature range as its wired sensors, and have IP67 ratings. IP66 means the device is dust proof and protected from strong water jets. IP67 means the device is dust proof and continues proper operation after temporary immersion in water one meter deep for 30 minutes.
But monitoring temperature isn’t only for food and beverage production. At American Crystal Sugar (ACS), monitoring motor bearing temperature and current is a way to prevent a potential calamity, such as a sugar dust explosion. “We first identified equipment and devices that were potential ignition points,” says Gary Phelps, ACS electronic control technician. 
The real challenge was installing an instrument network in the sugar silos. “The sugar silos are about 75 ft. high and 100 ft. across,” says Phelps. “A rotating bridge spans the top, and a tube down the center holds the motor where some of the bearing temperature and motor amp measurements needed to be made. Conventional instrumentation proposed a huge challenge in this area.” The silos, which are made of a heavy gauge stainless steel, posed a tough challenge for wireless. 
Since the sugar silos had rotating equipment, a mixed solution of WirelessHART and wired instrumentation was used. Each of the three silos has one Emerson Smart Wireless Gateway with four Rosemount 648 single-point wireless temperature transmitters installed; two measure bearing temperatures on motors; and two measure motor amps. Rosemount 848T wireless transmitters were also used on nine conveyor belts to measure eight temperature points on each conveyor.
As a result of the wireless installation, ACS has improved plant safety and pond management, obtained greater visibility in hazardous areas and seen a 2.5 percent reduction in operations time for higher operator productivity. It also is ready for new, upcoming EPA reporting requirements. 

Beyond temperature

Omega’s Desai lists other applications for wireless solutions. “In one application where local display was not needed, a sanitary flow sensor [FTB-401A] was used in the process location and wired to a wireless process transmitter [UWPC-2-NEMA].” The process transmitters have allowed processors to add pH monitoring, load cell and automation sensors to be tied into the wireless solution, providing a more complete picture of the process.
However, wireless systems are not limited to relaying temperature readings. Karschnia lists other important process variables including pressure, level, flow, pH, ORP, vibration, position, discrete I/O, corrosion, acoustics and gas detection. Using acoustics, Emerson Process developed a wireless sensor for steam trap monitoring. Steam traps, a common source for energy loss, discharge condensate and non-condensable gases with a negligible consumption or loss of live steam, preventing equipment damage. Often these devices fail. “Emerson now offers an acoustic sensor that is used to detect the state of these steam traps by listening to the sound that is made when steam flows through them and monitoring the trap temperature,” says Karschnia.
Energy monitoring variables are excellent candidates in both brownfield and greenfield applications, according to Robinson. “In brownfield applications, typically conduit runs and connections to host control systems are exhausted, and installing additional conduit runs, cabling and new I/O hardware/cabinets is cost prohibitive and increases the CAPEX spend [capital expenditures] on these projects. The increase in CAPEX spend makes these projects lose out to other CAPEX projects which can provide a greater internal rate of return for customer profitability,” says Robinson. “Wireless solutions can help reduce those upfront costs, but one still needs to consider and mitigate risks such as equipment RF [radio frequency] noise, radio [signal] penetration through existing infrastructure [buildings, walls, mezzanines and piping] and network topology reach.” The most important variables that affect energy costs are water (volume consumed), air (pressure, flow and temperature), gas (pressure, flow and temperature), electricity (kWw/mW consumption and peak demands) and steam and condensate return (pressure, flow, temperature, pH and DO). 
Although brownfield applications are problematic when it comes to installing wired systems, wireless systems represent a good alternative. “The Heinz Foods facility in Freemont, OH used our solution for exactly this purpose,” says Cooper Bussmann’s Toteda. “The cost and complexity of installing a hardwired system would have included repaving parking lots between buildings. The points measured were electrical consumption via kWh meters, water via flow meters and gas via gas meters. To ensure wire-like performance for the signals, frequency-hopping technology was combined with mesh networking techniques. The changing frequency hops around interference, and if one link is lost, the mesh ensures any other radio can act as a repeater.”
In another application, the Dutch powder mix provider, Huijbregts Groep, used to mix powders in manually loaded mixers, which involved moving the individual powders to the mixer and the finished, mixed powders to a packaging area. Redesigning the plant called for 24 mobile mixers with 1,500kg maximum capacity running on a common power rail mounted on the factory ceiling. While power wiring was doable, controls wiring was another story. Every mixer has an IP66 7.5 kW Danfoss VLT AutomationDrive on board, each connected to a PLC through wireless PROFINET. Positioning the mixers is handled by a VLT Smart Logic Controller as they are moved around on automatic wagons, also connected to PLCs via wireless PROFINET. Besides speeding the production process, the wireless automation system makes troubleshooting easier.
In a similar application, getting data to and from rotating tables in a beer barrel filling plant was done through friction-based slip rings that proved problematic. In an upgrade to the Plzeňský Prazdroj, a.s. (SABMiller Group) barrel filling plant in the Czech Republic,  British system integrator FMA used wireless Scalance W784-1 access points to replace the transmission line to the rotating tables. Two stationary, IP65-rated Scalance W786-1PRO access points communicate wirelessly with the Scalance W784-1 client modules on each of the rotating tables. This enables maintenance-free operation and provides maintenance engineers access to the entire Profinet network and the linked components via standard or wireless PCs—during operation and from any location within the plant. 

Distance/coverage issues

Early on, wireless systems were used by utilities for SCADA purposes. These systems often covered ranges of 20-30 miles and relied on high-power, licensed radio operation—typically VHF or UHF narrowband. Today, unlicensed wireless technology can cover ranges of several miles through mesh networks and repeater systems, and public cellular systems can offer advantages with certain provisos. 
“In larger areas where there are many obstructions and long distances to cover, we typically find that unlicensed 900 MHz radios will cover most applications,” says Phoenix Contact’s Shade. “With typical transmit powers being one watt, and the equipment having the functionality to add repeaters if necessary, unlicensed products can cover a long range of distance.” Unlicensed equipment incurs no licensing fees and causes no delay in waiting for paperwork to be processed.
“The reach of our wireless networks can span several miles due to the meshing technology used,” adds Karschnia. “We have many deployments of this technology in upstream oil and gas fields that cover hundreds of square miles.”
This is the same concept that covers small areas in a plant. Elevating an antenna can increase range. To bring process measurements back from a wireless sensor network, WiFi and WiMAX technologies can be used, and these are unlicensed in many areas of the world. The cost of installing these wireless backhaul networks has been demonstrated to be easily 50 percent less than the cost of a fiber-optic network that has to be trenched—depending on the distances and local labor rates, according to Karschnia.
“There is no one network technology that can solve all application [problems],” says Robinson. The considerations are many: distance, bandwidth, speed, security, communication protocols, industry standards, compliance and so forth. “Changing the physical media from a copper/fiber solution to a wireless solution does not make that any less daunting. For example, Endress+Hauser provides a wireless offering based on an industry standard, Wireless HART, which has a certain range of practical applications based on the above considerations.” 
Increasing the physical coverage typically means adding new communication adapters/repeaters and communication gateways indefinitely. Cell phone technology, also available from Endress+Hauser, is implemented today and is used regularly on delivery trucks and silos typically that are remote to processing plants, according to Robinson. 
“Implementing to a different, higher-power solution will always be a practical solution when the lower-powered solution cannot meet the application or environmental requirements,” adds Robinson. “Sometimes equipment RF noise washes out the non-licensed and low-powered wireless spectrum ranges, and you have to go to a higher power.”

Wireless, an economical choice

Wireless can save money in a number of ways. First, wireless sensors in a mesh network eliminate wiring and improve reliability. “Costs are saved in the project execution,” says Robinson. “Actually, the material costs of a wired and wireless solution are very similar. Thus the complete project has to be considered to see the big advantage of wireless. For example, Endress+Hauser’s WirelessHART solutions provide typically a project cost saving of 50 percent.”
“Wireless cost savings can easily be calculated by looking at the amount of wiring, terminations, drawing and time [labor savings],” says Karschnia. “We see savings ranging from 30 to 60 percent over a wired solution.”
Conventional sensors coupled with wireless I/O is a second way to save money with wireless solutions. When considering the option of buying standard sensors and creating a wireless means of communication versus buying wireless sensors, one thing to consider is how the sensors are going to be laid out in the application, according to Phoenix Contact’s Shade. “If the sensors are going to be somewhat clustered together, the option to run multiple sensors into one wireless device may be a way to save some money. With wireless I/O systems being able to accommodate upward of 50 to 100 I/O points per radio, buying standard sensors and using an external radio solution could be a very economical option.”
“We don’t make the sensing element, but instead get that data and make it wireless,” says Cooper Bussmann’s Toteda. “Therefore, with our solution, you can use the same low-cost sensors already specified and simply connect them to the communications system for seamless integration.” Toteda says a simple system can start at $1K for the radio, antenna and enclosure, and can go up to $2-3K per site. 
Besides process measurement accuracy, the cost of downtime when a wireless sensor needs to be maintained or calibrated must be considered, according to Omega’s Desai. The type of process being monitored will determine what feature may or may not be needed and affect cost of the sensor. The cost of batteries versus availability of stable AC power also may affect choice of the sensor. “The zSeries and wSeries product lines from Omega offer [processors the opportunity] to buy a calibrated probe without sending the transmitter back,” adds Desai. NIST-traceable calibrated probes can be changed in the field while maintaining the same transmitter in place, which cuts down on maintenance time, according to Desai.

To control or not to control

However, for many obvious reasons, performing control functions via wireless presents some problems, for example, response time and verification. “The most common method of verifying that a valve moved is to include a feedback signal,” says Toteda. “Wireless control has been used for decades in many critical applications/industries. Our own products have been used successfully for over two decades since there were 1,200 baud FSK [frequency-shift keying] modems.”
“Recently, we have used a 900 MHz I/O solution to send remote on/off control commands to remote pump carts at Bogle Winery in California,” says Phoenix Contact’s Shade. “We also use a small controller to send commands to one of two pump carts in the tank farm, which tells the cart which wine press to pump to. This system is in the middle of an upgrade due to their need to add four more pump carts and two more wine presses to their automated system.”
“Today’s wireless technology enables you to safely control any process loop that changes slowly over time, e.g., filling a large tank that takes hours, monitoring a vessel’s pH for a reaction to complete,” says Karschnia. Verifying or measuring a controller response is no different for a wireless device than it is for a wired one—except there is no scaling factor for a four to 20 mA signal because there is no wire.
“Emerson recently released a battery-operated pneumatic valve,” says Karschnia. “Prior to that, almost all wireless control loops were implemented with a wireless input and a wired final control element. 
“If you have a smart HART-wired valve connected to an older legacy control system that cannot process position feedback information from the valve, a WirelessHART THUM can be connected to the valve, and its diagnostic information can be wirelessly monitored by an asset management solution,” adds Karschnia.

Connect everywhere but safely

Today’s wireless systems can retrieve data from sensors and beam it to operators or managers in the plant or anywhere around the world through Internet-based PCs or wireless smart phones. While wireless mesh networks such as WirelessHART are relatively easy to deploy, Wi-Fi networks can pose more problems, especially with the variety of equipment that is often used, according to Karschnia. With wireless video cameras, RFID location tracking systems and mobile handheld devices on Wi-Fi networks, these networks should be planned well for coverage, interference and security. Consequently, setting up these networks may involve a controls supplier, system integrator and the processor’s IT department.
Cellular devices with virtual private network (VPN) capabilities are becoming very popular because they allow users to connect from anywhere in the world, says Shade. Wired firewalls and VPN routers can extend security. Best practice is always to password protect wireless networks and use WPA2 security with AES 256-bit encryption. 
The use of proprietary radio systems like Phoenix Contact’s 900 MHz Trusted Wireless or Emerson’s Smart Wireless technology is another way lock in security because only radios made by the same manufacturer can communicate on the immediate wireless network. According to Karschnia, Emerson’s wireless security solution has been tested by some of the largest organizations in the world and has been found to be more secure than many wired systems in use today.
For more information:
Bob Karschnia, Emerson Process Management, 952-949-7552, bob.karschnia@emerson.com
Justin Shade, Phoenix Contact, 717-944-1300, ext. 3524, jshade@phoenixcon.com
Ashish Desai, Omega Engineering, 203-359-1660, ext. 2326, desai@omega.com
Steven Toteda, Cooper Bussmann, 925-924-8500, steven.toteda@cooperindustries.com
Michael Robinson, Endress+Hauser, 801-208-9424, michael.robinson@us.endress.com
Frank Uhlemann, Eckelmann, +49 611 7103-0, f.uhlemann@eckelmann.de