Digital valve control

Emerson’s Fieldvue DVC6200 Series digital valve controller has racked up more than 1 billion hours of on-line use within the process and energy industries since its introduction in 2010.

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 because of its resistance to high levels of vibration as well as its Foundation Fieldbus communications capability.

The digital valve controller has saved the facility $40,000 per year in the cost of replacement instruments, plus that of lost production and labour.

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.

To overcome this problem, 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 programme 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.

At a nuclear power plant in the US, DVC6200 digital valve controllers have been 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 $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, removing the need to make a plant visit.

Emerson Fieldvue product manager Steve Hagen credits the instrument’s linkage-less, non-contact feedback system as one reason behind the quick adoption by industry and the 1 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,” he says.