Corrosion-resistant butterfly valve, available in large diameter sizes up to 12 inches, incorporates a double eccentric operating principle that provides improved wear and easier operation over traditional eccentric style butterfly valves. Typical applications include industrial water treatment, potable water treatment, swimming pools, water parks and waste water systems in such industries as chemical, chemical distribution, electroplating and power plants. Key to the valve’s double eccentric disk design is the off-center shaft that allows the disc to completely disengage from the disc seal, even when partially open. This reduces seal friction and improves seal wear characteristics, resulting in longer service life, minimal maintenance and better protection against pressure surges. The double eccentric design also lowers the torque required to operate the valve, making for easy manual operation and use of smaller actuators at a significantly reduced cost. Other outstanding characteristics include bi-directional capability and a high psi rating not normally associated with large diameter sizes. The Type 567 also features a specially engineered body seal with a Q-shaped O-ring that eliminates the need for flat gaskets and is compatible with any flange adaptor design, including those with serrated faces. The wetted inner body, plus the disc and bearings, are made of the same material as the corresponding pipe material for improved fit as well as corrosion and chemical resistance. The inner body, discs, and bearings are available in PVC, CPVC, PP (polypropylene) and SYGEF® PVDF (polyvinylidene fluoride) materials.