Double Half Shaft Wafer Butterfly Valves

Double Half Shaft Design | Disc Without Pin

The G.A. drawing of double half shaft wafer type butterfly valve, bare shaft with ISO 5211 mounting flange.

The double half shaft design is a typical pinless-disc design for wafer type butterfly valves, in which the disc is attached to the shaft by using profile connection rather than by using taper pins. Double half shaft is a jargon in comparison with the single through shaft in pinned disc design. Two half shafts are furnished for this wafer butterfly valve: the upper shaft and the lower shaft. As illustrated in the G.A. drawing above, the upper shaft (item 5) is attached to the disc (item 4) by using profile connection at its lower end that has a reduced diameter. The profile connection can be further classified into spline type, square type or flat type, through which operation torque is transmitted from the shaft to the disc. The lower shaft (item 3) inserts through from the bottom of the valve body and fits into the machined hole in the lower section of the disc. It mainly provides support to the disc. The axial movements of the upper shaft and lower shaft are blocked by the pins (item 6 and 6′), respectively. Only rotary motion can be transmitted. This disc without pin design eliminates possible leakage from the crevice formed between the pin and disc in pinned disc design.

Design Standards & Operation Methods

A double half shaft wafer type butterfly valve, ductile iron body and SS 316 (CF8M) disc, handle lever operated.

The double half shaft wafer butterfly valves can be designed in accordance with MSS SP 67, ISO 5272, BS 5155, EN 593, DIN 3202, API 609 and JIS B2002. When installed, the valve shall be sandwiched between two pipe flanges using a through bolt connection. The drilling pattern of the valve shall be in compliance to that of the mating pipe flanges. Various operators can be mounted onto the ISO 5211 connection pad. These include handle lever, worm gear, pneumatic actuator, electric actuator, electric & hydraulic actuator, etc.

Material Selection & Structural Dimensions

Drilling Pattern & Pressure Ratings

The drilling pattern of double half shaft wafer type butterfly valve shall be in accordance with BS 4504 PN10/PN16, BS 10 Table D & E, AS 2129 Table D & E, DIN 2501 PN10/PN16, JIS B2220 10K & 16K, ASME B16.1 Class 125 & ASME B16.42 Class 150, ISO 7005-2 PN10/PN16, ASME B16.5 Class 150.