Steve Hagen, FIELDVUE Product Manager, credited the instrument’s linkage-less, non-contact feedback system as one reason behind the quick adoption by industry and the billion operating hours. “We’ve eliminated physical contact between the valve stem and the instrument, which means it can withstand the high levels of vibration and corrosion often found in process environments.”
In China, at one of the world’s largest integrated chemical facilities, instrument engineers were faced with pipeline vibration that was destroying a steam service valve’s instrumentation. Since it was not feasible to change the process conditions or piping, the valve positioner had to be replaced about every three months.
To solve this problem, a DVC6200f was installed to take advantage of the unit’s resistance to high levels of vibration as well as its FOUNDATION fieldbus communications capability. The digital valve controller performed accurately and reliably, saving the facility €29,000 (US $40,000) per year in the cost of replacement instruments plus that of lost production and labour.
DVC6200 digital valve controllers are highly suited to a wide variety of industries and applications, earning high praise from companies that employ its technology to improve plant availability. At an ammonium nitrate facility in Australia, liquid ammonia valves face high-cycle service conditions and a surrounding ammonia-rich atmosphere. Both factors combine to create one of the most severe environments to be found in any processing plant, which could lead to valve failures and lost production.
Emerson engineers recommended the DVC6200 because its linkage-less, non-contact feedback technology can withstand these harsh conditions. The mine’s instrument technician installed the instrument on critical ammonia service valves, commenting that the digital valve controller not only proved easy to program and set-up but also that its on-line monitoring capabilities allowed operators to safely avoid manual checks and valve repairs in areas filled with ammonia vapours.
Additional user benefits include the availability of equipment alerts that notify of pending issues, automated configuration, calibration and tuning, and access to advanced levels of valve assembly diagnostics. With the Performance Diagnostic capability of the DVC6200 digital valve controller, questions about valve performance can be answered without pulling the valve from the line.
At a nuclear power plant in the U.S., DVC6200 digital valve controllers were installed to avoid failure of critical control valves in the plant’s feedwater system. An unplanned shutdown in a plant of this station’s size could cost up to €71k (US$1 million) per day in lost revenue.
The digital valve controllers at the plant provide real-time information about valve position and condition, including variables such as valve packing friction. In one instance, this data alerted plant operators to a loss of packing in a feedwater regulator, avoiding a plant trip.
Maintenance technicians decided to inject sealant into the valve’s packing box to keep the valve in service until the plant’s next scheduled outage, almost 18 months away, explaining that delaying any repair would not have been possible without the FIELDVUE instrument. They reported that the DVC6200’s accurate friction monitoring and measurement kept the system stable while packing friction dropped from 227 kg to zero during the sealant injection. The instrument’s fast response kept up with the changing friction load in spite of the valve’s heavy chatter, keeping the valve online and avoiding a costly shutdown.
In addition to the power industry, there are others such as pulp and paper, and offshore oil production that typically prefer to isolate valve-mounted instruments from harsh environments. With the DVC6205, only the valve position feedback is mounted on the control valve, while the remainder of the digital valve controller can be mounted over 90 metres away in a less severe or more accessible environment. With no linkage to wear, loosen, corrode or vibrate, the feedback unit can withstand a plant’s operating extremes.
As shown by the DVC6200 Series 1 billion operating hours, FIELDVUE digital valve controllers prove highly suited to challenging process requirements, including verification of safety shutdown systems, withstanding exposure to corrosive atmospheres, and meeting rigorous topside safety standards. The DVC6200 series is offered with CSA, IECEx, ATEX and FM hazardous area approvals as well as other certifications/approvals, such as Lloyd’s Register for industrial, marine and offshore use.
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