We Energies Gets Connected Using HART and WirelessHART Communication in All Plant Life CyclesPROJECT OBJECTIVES
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SOLUTION
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RESULTS
- Reduced valve wear, longer service life and improved reliability
- Substantial cost savings by monitoring valve condition remotely and identifying valves that are leaking steam or losing instrument air
- Extended service life of critical, and expensive, valves
The largest U.S. utility-owned co-generation facility in the United States helps keep the lights bright in Milwaukee. HART-enabled valve positioners reduce wear, extend service life and improve reliability for better boiler control and more efficient steam production.
We Energies’ Valley Power Plant, as the largest utility-owned co-generation facility in the country, has a unique need for reliability. HART-enabled intelligent valve positioners, also called digital valve controllers (DVCs), play a key role in providing that reliability in all life-cycle phases of operation including design, construction, device configuration, loop check, operations, maintenance, troubleshooting and insurance compliance testing.
The plant, which began operations in the late 1960s, produces steam and electric service. Two steam units, each with its own pair of boilers and a single extraction steam turbine-generator, each have generating capacity is 140 MW of electricity.
Reliability is especially critical because unlike other plants, where replacement power can be obtained from other plants on the grid, at Valley Power Plant, “if the plant loses its District Heating Steam System much of downtown Milwaukee will be without heat,” says Todd Gordon, computer instrument technician leader at We Energies' Valley Power plant in Milwaukee.
In his 30-plus years with We Energies, Gordon has helped the coal-based co-generation facility convert its automation platform from analog control to microprocessor-based distributed control. In that time, HART Communication has grown from use with handheld communication devices in the 1980s to laptops to a permanent connection with asset management software running in the control room.
“HART smart valve positioners have been used since 1999, and have provided valuable diagnostic capabilities that have allowed us to troubleshoot problems while the valves are in operation,” says Gordon. HART technology has also extended service live when installed on several older but still-viable control valves.
“In instances where we have installed a HART-enabled DVC on an older valve, my experience is that it makes a bad valve work better until a replacement can be installed. The nice thing is that we not only succeeded in deferring a capital expense this way, but when we decide the time is right to replace the older valve, we can also transfer the DVC from the older valve to the new valve assembly,” says Gordon.
The diaphragm of the valve in this photo (left) was changed twice
over the years before the valve was eventually replaced (right).
By 2005, the plant upgraded the laptop-based predictive maintenance software on the laptop, enabling it to communicate with HART smart devices to the DCS via multiplexers. This empowered instrument and control personnel to monitor smart devices online from a single location and gather information on their condition – remotely while the process was in operation. Evaluating valve condition in this manner eliminated the need to physically travel to field devices in favor of a comprehensive, online view of plant-wide diagnostics.
“That eliminated a lot of footsteps and saved time. Gordon says, adding that the laptop was replaced with a PC permanently connected via the multiplexers to smart devices in the field. The predictive maintenance software in the base station continuously monitors all connected smart devices, and issues status alerts when any of them exhibit behavior outside pre-established norms. The base station is also connected to the plant-wide LAN so the database can be accessed from any other site on the LAN using the standard Remote Access feature of Windows XP.
Other applications include remote access to diagnostic data from analytical probes measuring the amount of oxygen left in flue gases after combustion. “The information provided by those probes is critical to the efficient operation of the boilers, so being able to verify the condition of those measurement devices is yet another way technology is supporting plant reliability,” Gordon says, adding that a “roving” laptop is still used for field testing of calibration as needed.
Trending data are also part of the predictive program at the Valley plant, providing additional insight to instrument performance over time. Likewise, the free flow of data assists in reporting, training and presentations.
HART-enabled DVCs have brought several benefits. They have eliminated “chronic operating and maintenance problems” with desuperheating spraywater valves on all four boilers, says Gordon. They have also helped quickly uncover the root cause of problems for faster preventive maintenance response.
This was the case when an aging soot-blower regulating valve equipped with a DVC wasn’t working properly, but data visibility helped determine that the diaphragm was leaking excessive amounts of air -- leaking at least 350 standard cubic feet of instrument air per hour in addition to allowing a steam loss when the valve was supposed to be shut. “Instead of tearing apart the valve body and replacing the valve trim, which is an all-day job, we just replaced the leaking diaphragm, which only took a couple of hours,” Gordon says.
The problem was eliminated by installing a new $75 diaphragm that was “fairly easy to replace,” Gordon continues, “but more importantly, the time and expense of tearing apart a perfectly good valve were avoided, because the asset optimization software made it apparent that there was no problem inside the valve.” He estimates the instrument air-loss alone to cost the plant approximately $65 per month.
The digital valve controller on this rotary valve (above) was replaced with a new sliding stem valve (right).
Similarly, the access to smart valve data solved a sticky problem with inlet valves controlling the boilers’ water supply. Prior to having valve feedback to the control system, operators had no way to recognize valve-sticking. Today, when the DVC command signal and valve position deviate by more than 5% for more than 5 seconds, a status alert is triggered and operators can take corrective action before tank levels become critical.
This HART feature alone saved the plant from tripping off-line on several occasions, says Gordon. “We have been able to adjust valve packing on valves when they were in service, which is a huge benefit,” he explains. “We have also prioritized maintenance work based on the friction calculations of the HART smart positioners. The dampers with the highest friction numbers were repaired first.” (See examples below.)
The combination of HART technology with intelligent positioning control has reduced wear, extended service life and improved reliability of valves. In addition, the smart-communicating instruments provide better boiler control and more efficient steam production, according to Gordon, while remote monitoring of valve action through the DVCs creates substantial cost savings by identifying valves that are leaking steam or losing instrument air. And diagnostic support speeds troubleshooting to identify potential problems and provide an even, reliable supply of steam to downtown Milwaukee’s District Heating Steam System.
Decades of successive upgrades at Valley Power Plant lead Gordon to believe that “generally the technology pays for itself through improved operation and cost avoidance. In addition, they’ve found that the newer automated control systems work well, particularly when they receive accurate inputs from smart field devices.”
Looking forward, a new DCS upgrade will eliminate the need for remote communication through multiplexers because the DCS will interface directly with the plant’s asset management software. The success at Valley Power Plant has led Wisconsin Energy to broadly adopt HART Communication – including WirelessHART – across its many plants.
Wisconsin Energy Corporation is one of the nation's premier energy companies, serving more than 1.1 million electric customers in Wisconsin and Michigan's Upper Peninsula and more than 1 million natural gas customers in Wisconsin.
We Energies, Wisconsin Energy Corporation, has been recognized with the HART Innovative Achievement Award for exceptional achievement, ingenuity and innovation in using the Power of HART Communication in real-time applications to improve operations and maintenance and to realize greater benefits from intelligent instrumentation and automation system investments. In photo above, Ron Helson, Foundation Executive Director, presents the award to Todd Gordon (right), We Energies Valley Power Plant Computer Instrument Technician Leader, and Bob Vigansky, We Energies Pleasant Prairie Power Plant Computer/Instrument Technician.