Once you get free, it’s only natural to want to explore a little—and then a little more. Well, the same is true for wireless technologies in process control, which have evolved in recent years from cable-saving novelties to regularly specified solutions for bringing in signals that couldn’t be captured before. This move to the mainstream has also affected its users, and many are building on earlier wireless gains to extend their capabilities even further.
Such is the case with Hunt Refining Co., which adopted a pre-standard wireless solution for maintenance about six years ago in conjunction with a plant expansion, and came to appreciate and adopt wireless in its monitoring, reliability, optimization and safety applications. Hunt’s refinery in Tuscaloosa, Ala., is the largest supplier of paving and industrial asphalt in Alabama, much of which is used by nearby roofing shingle manufacturers.
The three-year, $1-billion expansion project was undertaken in 2010 to increase capacity at its 50-square-acre site from 52,000 barrels per day (bpd) to 72,000 bpd. As part of the expansion, Hunt built a hydrocracker, hydrogen plant, continuous catalyst regeneration (CCR) facility and dimethyl sulfate plant, and expanded its coker.
Alan Weldon, PE, technical services and safety director at Hunt, reports it began using wireless shortly after Emerson Automation Solutions introduced its initial systems in 2007 because the refinery needed to monitor tank temperatures in a remote location. “Our initial resistance was due to concerns about network reliability, security and integration into the existing DCS. However, acceptance grew as the wireless network was expanded to include sensing applications that address safety, environmental, reliability and process needs across the refinery,” says Weldon. “Potential savings also helped overcome resistance, and we installed three Rosemount 648 wireless temperature transmitters along with a 900-MHz 1420 Gateway and four additional 648s as repeaters. But we also had some bumps in the road.”
Wireless temperature monitors were added to more tanks at the Tuscaloosa facility the next year, but some power modules had to be replaced after less than a year of service. Weldon adds his staff and colleagues from Emerson determined that the existing, 900-MHz wireless network was experiencing choke points with too much data trying to pass through one wireless device on its path back to the gateway. Later, their journey into wireless continued when battery life issues delayed installation of more wireless temperature monitoring.
More reliability = more acceptance
Most end users, integrators and suppliers report that more reliable, higher-speed, easily installed wireless devices are driving its acceptance and expansion in the process industries. For example, where WiFi (IEEE 802.11a-n) or wireless Ethernet used to run at about 600 Mbps at 5 GHz in 2009, it sped up to 1 Gbps or higher at 5 GHz in 2013-14, and is up to almost 7 Gbps at 160 MHz at present.
Higher speeds have been accompanied by ongoing improvements of the primary wireless standards, including WiFi, ZigBee (IEEE 802.15.4), Bluetooth (802.15.1), Internet protocol version 6 (IPv6) over low-power wireless personal area networks (6LoWPAN) and other variants based on their radio, cellular, microwave or satellite roots. Several of these have been aided by the multiple-input, multiple-output (MIMO) method for multiplying the capacity of radio links by employing multiple transmit and receive antennas to use multi-path propagation, which improves data throughput and distance.
“We implement MIMO with four antennas, which allow multiple transfers of data in and out to enable very high reliability. We can send three streams and receive four, which make data packet losses much less likely,” says Divya Venkataraman, global product manager for wireless and network security at Rockwell Automation. “In addition, the wireless standards are continuing to evolve. IEEE, the WiFi Alliance and their partners are continuing to seek new ways to further eliminate data collisions and reduce network retries.”
Surveys and security essential
Despite these technical gains, pretty much everyone agrees that individual site surveys, audits and assessments, including radio frequency (RF) analysis, are still essential for deciding the best way to deploy wireless in each application.
“Audits can take into account distances, obstacles, noise, curvature of the earth and cellular coverage,” says Zechariah Hoffman, product marketing specialist for wireless at Phoenix Contact. “Some wireless technologies are more robust and may not need an audit, such as 900 MHz frequency-hopping spread spectrum (FHSS) because they can typically handle harsh environments. Wireless technologies operating in this frequency band usually have 1-Watt transmit power, which is the highest allowed by the U.S. Federal Communications Commission (FCC), making them ideal for many industrial applications. Using a licensed wireless frequency is another way to avoid doing an audit, but it also requires buying an operating frequency from the FCC.”
Hoffman adds that wireless is making similar gains on the security front. “Advanced encryption standard (AES) is a symmetric encryption algorithm on many devices, and there are various forms, such as 128-bit AES or WPA2-AES,” says Hoffman. “Frequency hopping on proprietary systems adds another form of security, which works because of the fast, constant changes to the frequency on which the radio is communicating. The pattern of frequency changes is different with each wireless network and manufacturer. Another security feature is Internet protocol (IP) or media access control (MAC) address filtering, allowing user access to only desired parts of the network.”
Juice on arrival, data too
Ironically, on either end of most wireless networks are transmitters or receivers with the usual wires for data and power, unless those devices are equipped with increasingly longer-lived batteries or the ability to draw power from their surroundings. For instance, to reduce cabling costs and secure remote temperature measurements without a power supply, Robinson Brothers Ltd. in Bromwich, U.K., recently began testing what ABB reports is the world’s first self-powered, wireless temperature sensor on the steam main supplying its chemical manufacturing plant (Figure 1).
The ABB WirelessHART temperature sensor with Energy Harvester requires no wiring, no external power supply, and ideally, no battery replacement. Its transmitter is powered by an onboard, micro-thermoelectric generator (micro-TEG), which is driven by the temperature difference between the steam pipe and the ambient surroundings. It measures the temperature of Robinson’s central heat distribution network at certain points, and transmits measurement values to its administrative building without needing added wiring inside its process building. Local system integrator ICA Services suggested the wireless sensor, and set up the transmitter to send data wirelessly to a remote wireless gateway, which feeds the signal into the company’s Ethernet network and then to an ABB SM500F data recorder.
In practice, the WirelessHART temperature sensor with Energy Harvester was installed in November 2012, and has been powered permanently since then by the plant’s process temperature, which is high enough to give the sensor a 100% power supply from its TEG module. The sensor needs a minimum temperature difference of around 30 °C, which is easily achieved by Robinson’s steam main, where the steam flows at around 106 °C and the ambient air is typically 26 °C. The transmitter also has a built-in back-up battery that isn’t used during normal operations.
“The transmitter has been operating for about three months, and it’s ticking all the boxes without drawing any power from its back-up battery,” says Tom Rutter, E&I manager at Robinson. “It looks like it could go on forever, provided there’s steam flowing through the line.”
To give users more data about their wireless applications, ABB also offers its SuprOS network management software and system, which can provide data about network traffic, signal strength, links to other components, device performance and damage. SuprOS works in conjunction with ABB’s TropOS self-healing, wireless mesh networking solution, and it can also perform remote configuration, maintenance updates and security patches.
“Our core network is TropOS mesh, and we can add unlicensed TeleOS point-to-point (PTP) or point-to-multipoint (PTMP) radios, or add licensed ArcheOS licensed PTMP radios to it, depending on the needs of the application and environment,” says John Yelland, global marketing vice president at ABB Wireless. “Then, they’re all managed by SuprOS, including some PTP devices we support.”
To get process data to cloud-based services and the Industrial Internet of Things (IIoT) via wireless, Smart Sensors Inc. just launched its low-cost Cloud Wireless Sensor System, which includes customizable, real-time monitoring, alerts and analytics. Users place its matchbook-sized, plug-and-play wireless sensors wherever they’d like to capture data, and they transmit relevant data via Bluetooth Low Energy (BLE) or RF to a Swift Sensors Bridge, which is a small appliance that connects the sensors to the secure Swift Sensors Cloud using Wi-Fi, Ethernet and/or cellular communications. Finally, administrators use a Swift Sensors web-based dashboard to configure the sensor system for data monitoring and analysis from any location.
“Our solution costs pennies on the dollar compared to other wireless systems, and installing our half-dollar-sized sensors is quick and easy,” says Sam Cece, CEO of Swift Sensors. “For security, we use time stamps and a closed network with only one access point and dual firewalls. This lets us safely tie in to legacy system from which users are looking extract data they couldn’t get before.”
Stay on the trail
Likewise, the more recent wireless hiccups at Hunt’s Tuscaloosa refinery began to be resolved in 2009 when Emerson’s Rosemount division adopted the WirelessHART protocol, and Hunt’s 900-MHz gateway was upgraded to a newer, 2.4-GHz WirelessHART gateway. Emerson’s AMS and Wireless Snap-On functions were also added to the gateway to address network stability and reliability concerns. “This made the upgrade easy and successful,” says Weldon. “The choke points and power module life issues were resolved, and that added to our confidence. As a result, when overfill protection was needed on a remote ethanol tank, we installed a Rosemount 702 Discrete Wireless Transmitter to a two-point float switch.”
Likewise, to improve reliability in 2010, Hunt implemented Rosemount 648 temperature transmitters for monitoring heat exchangers. For environmental compliance, it added a Rosemount 3051CD differential pressure transmitter and 648 temperature transmitter to monitor water flow and temperature to the nearby Black Warrior River.
In 2011, Hunt also added a Rosemount 775 The HART Universal Module (THUM) wireless adapter on a 3051 SMV transmitter to meet 40 CFR 98 reporting requirements for greenhouse gases. Following its success, Hunt added THUM to a MicroMotion Coriolis meter measuring asphalt to the coker to provide density and mass flow data. However, it also experienced intermittent communication issues, which delayed installation of more THUMs. “That added some angst,” adds Weldon. “But the difficulty was finally identified as a wiring issue, and it was repaired.”
In 2013, Hunt installed six Rosemount 708 acoustic transmitters on its Butane Bullet relief valves (Figure 2). These devices provide an added protection layer that notifies operators if a relief valve is beginning to relieve or leak. In 2014, the refinery added three Rosemount 848 high-density temperature transmitters on its diesel hydrotreater and combined feed exchangers. “They’d been experiencing issues with corrosion due to dew point moving in the heat exchanger train,” explains Weldon. “So the added benefit here was performance monitoring for fouling.”
In 2015, Hunt upgraded its wireless gateways to Version 4.0, which was required to install a PermaSense corrosion monitor and 20 sensors in the refinery’s coker and crude unit. Also, THUM was added to a Micro Motion meter on a crude feed tank to monitor flow, temperature and API gravity, and a CSi wireless vibration monitor 9420 was added to the coker jet pumps. “Finally, this year we added a Micro Motion high-capacity Elite Coriolis Meter with THUM to our oil movements area for custody transfer of asphalt,” concludes Weldon. “Smart meter verification diagnostic reporting is available wirelessly via AMS on the gateway.
“Our initial resistance to wireless was overcome by its demonstrated network and transmitter reliability, as well as the improved diagnostics from AMS and Wireless Snap-on. Our acceptance resulted in non-traditional monitoring applications in environmental, reliability and safety. So far, we have a total of 77 Emerson wireless devices and 20 third-party devices installed. The takeaway is, when we look at an application now, we immediately ask if we can do it with wireless.”