Developed in Japan, a ball valve that rotates off-center with a cam action is particularly suited for fluid processes employing high concentrations of particles such as slurries. The ball only comes into contact with the ball seat at the final stage of rotation, realizing sealing. Hence, there is no chance of particles becoming wedged between the ball and seat and causing surface damage, its supplier claims.
The setup is also said to minimize the possibility of seat materials contaminating fluids, which is particularly important for industries such as food processing. One such successful application in this industry was conveying a powdery starch syrup.
The supplier of the ball valve, Hisaka Works, also presented another innovation at the recent InChem show in Tokyo: a system that enables in-place seat replacement through the incorporation of a removable side flange.
The Duax-Window valve/seat combination brings significant savings in operating costs, according to Kazuhiro Haruta of the overseas sales department at Hisaka. The Duax ball valve is reportedly good for 10,000 cycles before it requires seat replacement, compared with around 100 for the company’s TF5 trannion-type soft seat ball valve (and approximately 500 if a metal seat is used, per the model TF5M). Hisaka estimates that a ball valve would typically operate 10,000 cycles in a single year.
So while the Duax-Window initial investment cost is around 80 to 100 percent higher than what it is with conventional ball valves, the running costs are said to be much lower. “Maintenance can be carried out by a single technician in one-tenth of the time required for a ball valve, where maintenance must be carried out offline [by removing the entire valve from the piping],” Haruta said.
Hisaka estimates that the lifetime cost of the Duax-Window ball valve is 45 percent lower than that of its own TF5 ball valve and 25 percent less than that of its TF5M valve, despite the higher initial investment requirement.
“Traditional maintenance can be particularly troublesome if a large ball valve is located high off the ground,” Haruta added. “This can entail using a crane for removal, which is costly.” All of the Duax-Window ball valves, ranging from 40 to 600 mm dia, can be serviced in place no matter how large they are, according to Hisaka.
Hisaka offers a variety of seat materials for the valves depending on the application. These include rubber seats for slurries, PTFE (Teflon) or polyetheretherketone (PEEK) seats for monomers and solvents, and metal seats for high-temperature fluids.