Throttling Butterfly Valves
This article is about some of the newer technology on the market for butterfly valves. What we have see traditionally in butterfly valves is a severe lack of control outside of the "sweet spot", which is between about 20% and 60% of rated Cv. The curve, instead of being the ideal equal percentage, looks considerably more like a linear line. This becomes an issue if the valve will ever need to effeciently control media. It makes operators and technicians have a difficult time tuning it and results in the classic "hunt and peck" for the positioners. However, butterfly valves have many postive characteristics, namely the size and weight, followed by the lack of soft seals in some designs (triple eccentric). When compared to a globe or segmented ball, the amount of material is quite considerable especially at larger sizes. This results in a savings for the customer and less line space taken up in the pipe.
Let's take a look at what Dr. Hans Baumann, who in many people's eyes is the founder of modern control valves, has to say about the recent advancements, and how the valve industry has adapted to overcome the negative aspects of the butterfly valve.