The valve body shall be one-piece lug design with extended neck to allow for 2” of piping insulation, have   flange hole drilling per international flange standards and be provided with a non-corrosive bushing and selfadjusting   stem seal   The valve disc edge and hub on metal discs shall be spherically machined and hand polished for minimum   torque and maximum sealing capability. The disc-to-stem connection shall be an internal double “D” design   with no possible leak paths in the disc-to-stem connection. External disc-to-stem connections such as screws or   pins are not allowed. The valve stem shall be one-piece design and be mechanically retained in the body neck   and no part of the stem shall be exposed to the line media. The valve seat shall be a bonded, tongue-and groove   design with a primary hub seal and a molded flange O-ring suitable for weld-neck and slip-on flanges. The seat   shall totally encapsulate the body isolating the body from the line media and no flange gaskets shall be required.   The valve shall be rated for bubble-tight shut-off for bidirectional and dead-end service to 250 psi (17.2 Bar) on   sizes 2”-20” (50mm-500mm).   The valve shall be tested for tight shut-off to 110% of the rated pressure.   The Valve shall have the following approvals and certifications: CE/PED Certification, NSF/ANSI 61-   2008 (Potable Water) Certification, SIL