INCREASING PLANT PERFORMANCE THROUGH
BECAUSE TECHNOLOGIES ARE BUILT
ONE UPON ANOTHER, WE FACE THE
QUESTION OF WHEN IT IS BEST TO USE
WHAT’S ALREADY IN PLACE AND WHEN
WE SHOULD INVEST IN NEW, ENHANCED
TECHNOLOGY. TODAY’S VALVE
DIAGNOSTIC DEVICES AND TECHNIQUES
OFFER MANY WAYS TO MAKE THOSE
DECISIONS EASIER. BY HARRY BURNS, PH.D.
For the wide variety of valve-related instruments in the field today—which range from current-to-pneumatic transducers to the newest digital valve controllers—
the technologies within the devices have been built on top of one another. This means
that the latest technology often offers features from the earliest. But this situation
leads to questions about whether it’s best to increase a plant’s performance by using
what is already there or by replacing it with a newer technology to take advantage of
You might ask another question, as well: What are the pneumatic instruments
accomplishing for the plant that have caused them to remain of value after all this
time? Consider these examples:
; An I/P Transducer allows the operator to adjust the signal from a central location.
; A valve positioner uses air pressure to move the valve and uses travel for feedback to control the process flow. Routinely, the control system does not receive
any feedback from a positioner.
; A digital valve controller on Foundation fieldbus allows control in the field and
feedback to the process control system. The synergy of control in the field and
integrated feedback lets the digital valve controller pass a threshold to become
part of the process control system itself, instead of just being another piece of
equipment the distributed control system manipulates.
To answer our questions, let’s look first at an example of a plant’s experience with the
latest technology, keeping in mind that, when integrating digital valve controllers in a
process control system, plant benefits vary. As we all know, control valves and instruments are complex assemblies that fulfill important control functions. To ensure that
processes, and ultimately the plant, perform at optimal levels, these valves/instruments
must operate as expected. Degradation of a single control valve component can impact
plant availability, throughput, quality and safety.
BOOSTING MAINTENANCE PRODUCTIVITY
The Solvay chemical plant in Tavaux, France applied digital control valve diagnostic
technology to get maintenance productivity gains of between 10% and 15%. To do so,
the plant used a combination of predictive maintenance software and digital valve con-