WirelessHART Solves Problems
By Paul Studebaker, Editor in Chief, Plant Services Magazine
Rapid, low-cost implementations take on issues from equipment diagnostics to plant optimization
Much is made of the ways WirelessHART™ unlocks the stranded information in wired HART devices, lowers costs and eases installation of process control points. But the driving force behind many implementations is solving urgent or painful problems in an ever-growing variety of innovative applications.
“This is where we see the main need for wireless,” says Eric Olson, product manager, device management instrumentation, ABB, “solving a real-world problem by getting information that wasn’t economical in the past, or specific information for the situation. It can be as simple as measuring ambient temperature in a remote location to understand what’s going on in a process.”
It’s clear that applications other than traditional process variables are on the minds of many early adopters. “We’re seeing many applications on the equipment itself rather than the process – on bearings, motors and pumps, for example,” says Jim Cobb, senior marketing manager, Emerson Process Management.
Otherwise impractical
Because of the high cost of wiring, many secondary process variables are not measured, and whole pieces of process equipment are without instrumentation. Wireless offers low-cost access to additional measurements and process variables that were previously not economically feasible. Installation cost savings of as much as 90% are estimated for wireless over wired applications.
Temporary measurements can be invaluable for troubleshooting process or equipment problems, and for confirming preliminary diagnoses. For example, Olsen says, “You can add temporary temperature measurements to a heat exchanger to confirm possible leakage using a spare thermowell or a contact probe.”
Operator rounds have been streamlined by replacing manually-read mechanical pressure gauges with WirelessHART pressure transmitters to reduce operator rounds. Often, these gauges are installed where there is no local power.
“The relatively low cost of WirelessHART now allows HART technology to be applied to devices which were not typically 4-20mA in the past,” Olson adds, for example, monitoring on/off actuation of effluent and safety valve operations for possible regulatory or safety incursions.
Quick and convenient
When one plant put in a temporary LPG supply line to keep production running while its main line was out for repairs, “They were able to quickly install flowmeters using wireless,” Cobb says.
On a pilot plant or flexible manufacturing facility, wireless instrumentation is easier to reconfigure for different monitoring requirements of various experiments or product setups.
StatoilHydro ASA uses wireless for onshore and offshore wellhead flow readings. Instead of manual measurements once a day, they know immediately when production falls off and can take action.
Engineers at the company’s Gullfaks A, B and C platforms in the Norwegian North Sea were losing flow when wellhead pressures dropped on any of 90 wells supplying the platforms. Early flow-loss detection helps operators reestablish flow by reducing pressure, bringing flow back quickly to improve throughput and production.
However, flow losses were hard to detect because there were no flowmeters in the well pipes. Manual readings were taken only at the beginning and end of a shift, so a flow loss could easily go undetected for a long time. A pilot project put wireless temperature transmitters to indirectly indicate flow on lines at each of 40 wells. Temperature readings are transmitted every 30 seconds from clamp-on temperature sensors surface-mounted on the flow pipes. “These typically take about two hours to install, compared with up to two days for a conventional wired unit,” says Geir Leon Vadheim, StatoilHydro instrument lead.
Tormod Jenssen, staff engineer for plant integrity at the Gullfaks field, adds that, “Wireless transmitters enabled quick and reliable detection of lost flow and allowed immediate action to reestablish flow and increase production.”
Plant optimization
Wireless also is being used to monitor additional variables for process and production optimization. Temperatures, pressures and flow rates that were too expensive to monitor at the operator console can now be brought there wirelessly.
“Adding a measurement can increase plant operational productivity,” says Olson. “In one case, wireless sensors were added to monitor a positioner and indicate when an air leak was causing unstable operation. This could result in the positioner being unable to fully close or fully open a valve.”
A similar system is used to compare the setpoint to the valve position, count strokes, measure time to reach setpoint, and monitor the valve signature to indicate a possible mechanical fault or need for valve maintenance.
“A wireless adaptor can monitor process variables from instruments such as a Coriolis flow meter to provide additional real process information – totalizer, pressure, temperature, density,” says Olson. The same can be applied to for multivariable pressure instruments. “This provides greater information to allow operations and maintenance to make better and faster decisions if problems are noticed.”
A wireless field device isn’t just a different kind of transmitter; it is a breakthrough in technology and practice, and plants are just beginning to explore the possibilities. “The adoption of wireless technology will be driven by the ability to extend and manage the flow of information around the plant truly without limits,” says Peter Zornio, chief strategic officer for Emerson Process Management. “This will drive work process and operational practice change as this new capability is utilized. That’s the definition of a technology discontinuity.”