DVCs Drive Digitization of the Process Industries

Emerson's Fisher FieldVue was introduced in the 1990s as the microprocessor-based replacement or conventional electronic and electro-pneumatic valve positioners. Not only did it enjoy a significant established market on Fisher's own valves, but Emerson claims that its digital communication and diagnostic capabilities changed the way all process control vendors monitor control valves and accelerated the process industry's move towards digital instrumentation.

Control valves represent much of the maintenance requirement on a plant and are blamed for a significant proportion of unscheduled downtime, so the valve performance diagnostics and alerts offered by Fisher DVC (Digital Valve Controller) units via HART and more recently Foundation fieldbus were seen as a major step forward. By 1999 Emerson was claiming an installed base of some 100,000 units, implying annual production of around 25,000 units, but since then the product has taken off, with Emerson now claiming to have sold a million units worldwide.

Even factoring in the effect of recent major projects in, for example, China, it seems that Emerson is now producing between 130,000 and 150,000 DVCs every year. That is confirmed by the October '08 Emerson announcement that the output of its Cernay plant in France had doubled between 2005 and 2008. Cernay is said to be responsible for half the European production of Fisher products, and its capacity was increased in 2008, particularly to accommodate larger sized valves for turbine by-pass and anti-surge applications as well as nuclear industry-compliant valves.

Paralleling the growth of the DVC product range has been the rise of Danny Nelson from Fisher mechanical test engineer supporting the new FieldVue instrument design in the mid-1990s to vp of Instruments for Fisher today. "From the early inception of the product, we focused on Fisher core product values -- reliability and performance," commented Nelson, recalling his earlier role. "Because the FieldVue instrument was the first communicating, loop-powered digital positioner, several new tests were developed to verify technologies deployed in the product."

Over the years increasing capability has been built into the Fisher device. Indeed the diagnostic capabilities of the latest version, the FieldVue DVC6000 Series, are such that Emerson claims that plants can operate for five to seven years between maintenance shutdowns. It's also offered with the option of Emerson's THUM adaptor, enabling an asset management engineer to communicate with the DVC over WirelessHART, independently of the main control system.

Unnecessary removals

Industry watchers estimate that 75% of the removals of control valves from service for maintenance are unnecessary. Enabling remote diagnostics via Emerson's AMS ValveLink software allows a better informed decision as to whether a valve needs servicing. And the benefits aren't confined to Emerson systems. As well as being used stand alone in HART or FF systems, or with AMS Suite: Intelligent Device Manager, via DeltaV, Ovation and Provox, it can also be used with Yokogawa's Plant Resource Manager (PRM) and Centum DCS while integration with Invensys and Honeywell hosts can be provided via HART.

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