Standing the test of time The Quadax four-offset butterfly valve is a patented design butterfly valve with all the qualities of the proven triple offset butterfly valves with unique features that offer significant advantages. Pipes, Pumps and Valves Africa finds out more. According to Patrick Hofacker of Mueller Quadax in Germany, innovation lies at the heart of the business today.
Whilst the concept of the fourth offset may be difficult to understand, these uniquely designed and patented butterfly valves are offering straightforward benefits. “Less wear, lower torque, higher Cv and unique seal options is what these valves bring to the table,” explains Hofacker. Previous valve designs Looking at past valve designs says Hofacker, first, there was the centric design with the turning point in the centre of the seat and the centre of the pipe. With the single offset (ball valve) the turning point of the disc is offset along the direction of the pipe, while the double offset saw the turning point of the disc also offset from the centre of the pipe towards the outer edge. With the triple offset, explains Hofacker, the seat has a conical shape. “The tip of the cone is offset from the centre of the pipe towards the outer edge. A circular cone results in an elliptical narrow seat in the valve body.” Due to the limitations with these designs, Quadax opted to find a solution that they say they have in the four offset butterfly valve. “In the case of this butterfly valve, the output cone uses is elliptical. By cutting at a specific
Pipes, Pumps and Valves Africa - May/Jun 2021
angle, it results in a round and thus larger sealing area.” Thanks to the metal to metal sealing it can handle higher demands, higher pressure ranges and higher temperatures and is proving to be extremely in demand in the cryogenic industry. Benefits According to Hofacker, the design is also very compact. “it can be produced in bigger sizes without being more costintensive, one of the reasons why butterfly valves have become more popular.” He attributes the design to the company’s problem-solving approach. “We had customers who were struggling with sealing especially in cryogenic applications. The triple offset valves were leaking in these applications and were problematic.” The fact that the material thickness was not the same all around was problematic. “In other words in very extreme temperatures, there was shrinking and expanding happening but not in the same dimensions and direction at the same time meaning the valve would leak.” He said it was clear that they needed to design a butterfly valved that kept its structure on one side straight while reducing the friction to almost zero. The only way to achieve this would be to have around sealed with the same wall thickness all around.