... API609, EN593. 3. Flange to: DIN PN10/16/25, ANSI B16.1 BS4504. cast Iron lug butterfly valve I) Design standard:1:Design ... standard conform to: MSS SP-67, API609, EN593.2 ... backed seat with stable valve torque.2. Grooved sleeve design to achieve stable positioning.3. Simple construction, small in size, Easy disassembling, ...