It's been decades since industrial maintenance was a "handyman's" vocation and many years since experts first showed us the differences between run-to-fail, preventive and condition-based or predictive maintenance (PdM). But it's only recently that maintenance professionals have gained practical access to the technologies they need to support PdM. Wireless networking is one of those enabling technologies. Today, plant-operating companies are turning to the industry standard, WirelessHART, for benefits that range from remote access to instrument diagnostics to enhancements to real-time process control systems.
Users of WirelessHART describe reduced engineering time and effort, easier and faster expandability once the wireless infrastructure is in place, access to previously impractical or impossible areas, and improved asset management through real-time diagnostics—often for the first time allowing companies to operate in a true predictive maintenance mode, and all without the need to run new signal wires!
The Flexibility to Change on the Fly
Vlad Goldenberg does a lot of work in continuous improvement, mostly in the area of thermal power generation. The senior engineer with Xcel Energy, Minneapolis, Minnesota, keeps busy managing a power plant performance testing program that has him and his team constantly analyzing data and devising new methods for testing assets and processes such as condensate feedwater, heating systems, gas and steam turbines, condensers and cooling towers.
This requires the test group to be constantly on the go, using an inventory of temporary transmitters and instruments mounted for testing.
Using an enclosure designed in-house to be mobile, they interface the team's wireless data acquisition system with the wired Modbus and OPC data acquisition network using an Emerson 1420 WirelessHART gateway (Figure 1). The box has eight connectors for wired HART transmitters where wires are still needed, plus a connection for a WirelessHART adapter, The Bullet, from MACTek, purchased via Moore Industries. The performance testing team has 16 of these, each communicating with eight instruments in HART multi-drop mode.
The extent of savings depends on the type of test, instruments and mounts used, but for starters, WirelessHART has reduced cabling requirements by half or more. This is considerable in light of the weeks it can take to set up a heat balance test involving 100 instruments or a cooling tower test, which used to require up to 500 feet of cabling per instrument. "On average, we've seen between a 15% and 30% reduction in setup and teardown time and labor," which Goldenberg says is more significant than savings in wiring costs.
Field instruments connect to the enclosure via short cables wired using HART multi-drop mode, and the data is collected by the Bullet, then sent via WirelessHART to a central data acquisition system. "We're using these instruments in digital multi-drop mode," Goldenberg says, "and it's worked really well for us."
Streamlines Overfill Protection
"We make everything out of a barrel of oil," says Chris Smith, instrument and controls engineer at the Shreveport, Louisiana, facility of Calumet Specialty Products Partners.
The plant uses a WirelessHART-based radar tank overflow protection system from Endress+Hauser that replaced a museum-worthy tape-and-float tank gauging system rife with mechanical issues. The old system featured a gearbox on the ground that served today's transmitting function, a proprietary network that would knock out whole sections of the tank farm if one went down, and mechanical issues that could require tanks to be taken down for maintenance, which, as Smith notes, is "an extremely big deal."
Compared to WirelessHART, adding a single tank overfill protection using wires would require a week or more of digging and running wire and could be "more expensive by orders of magnitude," Smith says: "By some estimates it would have cost us four times as much just for the installation."
Today, wireless adapters handle two instruments (and signals) per tank, one for temperature and one for level. But Smith sees the potential for running multiple temperatures to ensure mixing and heating uniformity inside tanks, "which would be very easy; we'd only need an additional instrument and essentially nothing else," he says, since the wireless infrastructure is already in place. Instrumentation and wireless adapters mount together atop each tank at the radar transmitter, eliminating remote-mount wiring. The wireless adapters, which double as repeaters, have carried signals hundreds of feet. Currently, the facility has roughly 75 wireless instruments in two tank farms, and "it's growing on a weekly basis," Smith says.
Prevents Energy Losses and Shutdowns
WirelessHART allows once-ignored conditions in the field to be continuously monitored and data on sub-par assets to be communicated easily to the control room for rapid analysis, diagnosis and corrective action.
Kerry Phillips, global manager of the Smart Services Group at Armstrong International, explains that after a century of machining and distributing iron and steel products for steam, air and hot water applications, the "main new factor" in the company's move into electronics and isntrumentation has been wireless technology. "It has now enabled us to provide automated, real-time monitoring solutions for system reliability and efficiency."
Armstrong entered the world of WirelessHART by opening its proprietary wireless systems to new WirelessHART-based acoustic, temperature and steam trap monitoring solutions. The justification for such systems begins with savings. Lost energy from a single steam trap can cost a company anywhere between $4,000 to $7,000 a year" according to Phillips, and a 10% percent failure rate isn't uncommon at large process facilities such as oil refineries and petrochemical plants, which typically have 5,000 or more steam traps installed.
Additional justifications go beyond simple ROI. Plugged steam traps, for instance, can cause condensate to back up and cool in steam lines, causing pipe corrosion, water hammer and possibly solidification of material in process pipelines — particularly sulfur lines at refineries — which raises the risk of downtime and catastrophic failure at industrial plants.
Such are the motivations of a refinery in Mexico, which uses Phillips' wireless steam and relief valve offerings to monitor and send signals to the control room for analysis, process improvement and energy savings. And it's why a Middle East refinery now under construction includes 2,600 wireless steam trap monitors in its design.
Minimizes and Eases Flowmeter Calibrations
One hydrocarbon processing plant uses WirelessHART technology to achieve a more proactive, predictive maintenance operation, specifically with regard to the Coriolis mass flowmeters used throughout the plant. The problem was that these instruments were subject to repeated, time-consuming testing and calibration routines. This was done manually, and because wired multiplexers were deemed impractical and cost-prohibitive to install, calibrations required removing and reinstalling each instrument. This was the source of considerable reductions in plant availability.
While the shutdowns were planned, they were also costly, so the plant sought to increase calibration intervals using continuous monitoring of diagnostic data, thereby allowing technicians to calibrate each instrument only when needed.
A WirelessHART communication network from Pepperl+Fuchs accomplished just that. The system continuously monitors each Coriolis mass flowmeter's "health" from a central point at the engineering and maintenance station. Now, not only have work orders been reduced, but technicians calibrate Coriolis flowmeters in situ "instead of having to take them out of the plant and into the shop," says Gerrit Lohmann, manager of the remote systems product group of Pepperl+Fuchs. He adds: "Before, one person was employed full-time calibrating the meters once a year, now they calibrate them twice a year on command."
This implementation of WirelessHART provided critical transparency of system components from the control room down to the field device level, and opened new opportunities for requirements-driven, preventive maintenance routines.
The network further allowed the plant to recoup significant uptime and financial benefits because calibrations are no longer performed at fixed intervals, but when required, as determined by the parameters regulated by the WirelessHART-based continuous monitoring system.
Lohmann also tells of a South African refinery that tapped WirelessHART to access data needed for leak detection of crude oil in approximately 50 tanks. The wireless protocol met the refinery's need for intrinsically safe equipment, overcame issues of accessing hard-to-access assets, improved monitoring and maintenance capabilities, and safely brings variables from a hazardous location in the field into the control room.
Competitive Edge for Frigid Climates
A tank truck rental company with a fleet of more than 100 trucks is saving $4,000 per tank it hauls, every time it's rented. How?
The company operates in a region where temperatures frequently fall below -30 ºC (-22 ºF). Employees of companies renting the tank trucks rarely wanted to step outside to monitor and record levels. There had been many cases where they wrote "essentially any old number" in reports they would present to their supervisors, according to David Burrell, product specialist with Phoenix Contact. Industry-wide, this has led to problems such as undetected oil thefts and cases of overflow and regulatory noncompliance.
Recognizing the risk — and competitive opportunity — Burrell's customer sought a remote monitoring solution. A wired approach wasn't feasible, and of the wireless solutions, WirelessHART was the most sensible choice because it allowed the tank rental company to easily and quickly retrofit adapters to its existing tanks, which had already been using HART instrumentation.
Now all tank levels can be monitored simultaneously, in real time, from a single seat in a control room. Risk, frostbite, labor and costly errors have been eliminated. The company estimates a reduction of approximately $4,000 in installation costs for each tank, every time it is rented.