AWWA C504 pdf download.Rubber- Seated Butterfly Valves
Permeation
The selection of marerials is critical for water service and distribution piping in locations where there is likelihood the pipe will be exposed to significant concentrations of pollutants that are comprised of low molecular weight petroleum products or organic solvents or their vapors. Research bas documented that pipe materials such as polyethylene, polybuylene, polyvinyl chloride, and asbestos cement; and elastomers, such a5 used in jointing gaskets and packing glands, may be subject to permeation by lower molecular weight organic solvents or petroleum products. If a water pipe must pass through such a contaminated area or an area subject to contarnination, consult with the manufacturcr rcgarding pcrmcation of pipe wall, jointing materials, etc., before selecing materials for use in that area.
4.3.3.2 Connection. The connection between the shaft and the disc shall be designed to rransmit shaft torque equivalent to at least 75 percent of the torsional surength of the minimum required shaft diameters. Rigid shaft restraint shall be provided. Hardware used in connecting the shaft to the disc shall be of corrosion- resistant metals. The disc shall be mechanically secured to the shaft by a process such a bolting, rivering, threading, upserting, or cross pinning, and shall not rely solely on chemical bonding, adhesives, or welding. The shaft shall be capable of nondestructive separation from the disc.
4.3.3.3 Size. The portion of the shaft that extends through the valve bearings shall be full size. If the valve shaft diameter is reduced to fit conections to the valve operating mechanism, the smaller portion shall have flles with radi cqual to the offset to minimize the possibility of stress concentration at the junction of the two different shaft diameters. The smallest diameter of the shaft shall be capable of transmitting the maximum calculated valve-operating torque without the torsional shear stress exceeding 40 percent of the yield strengch of the shaft material. In aulditioi, Iaxinun valve shafi suresses in the full-size portion of the shaft shall not excced the lesser of 75 of the tensile strength or 13 of the yield sttength of the material used. Tensile and yield strengths shall be based on the minimum strength stated in Sec. 4.2.2.AWWA C504 pdf download.