AWWA C500:2019 pdf download.Metal- Seated Gate Valves for Water Supply Service
4.2.1 General. Materials shall comply with the requirements of the Safe Drinking Water Act and federal regulations for potable water, wastewater, or reclaimed water systems as applicable. Valves used in potable water service shall be certified to NSF/ANSI 61.
4.2.2 Permeation. The selection of materials is critical for potable water, wastewater and reclaimed water service and distribution piping systems in locations where there is likeliood the piping system will be exposed to significant concentrations of pollutants composed of low-molecular-weight petroleum products or organic solvents or their vapors. Documented research has shown that piping system materials (such as polyethylene and polyvinyl chloride) and elastomers used in gaskets and packing glands, are subject to permeation by lower-molecular-weight organic solvents or petroleum products. If a potable water, wastewater, or reclaimed water piping system must pass through such a contaminated area or an area subject to contamination, consult the manufacturer regarding permeation of pipe walls, valve components, jointing materials, and other piping system components before selecting materials for use in that area.
4.2.3 Dissimilar metals. In the presence of an electrolyte, direct contact between metals of dissimilar corrosion resistance may result in galvanic corrosion of the more active, less corrosion- resistant material. When dissimilar metals must be used for internal parts, the rate of corrosion shall be reduced as much as practical through the selection of materials that exhibit similar resistance to corrosion by placing a dielectric material between the metals or by applying a dielectric coating. When contact between dissimilar metals cannot be avoided, the assembly shall be designed so that the resulting corrosion will be minimized and will not adversely affect water quality or result in malfunctioning or premature failure of the assembly.
4.2.4 Mechanical and chemical properties. The requirements of ASME, ASTM, AWWA, or other standards to which references are made in this text shall govern the mechanical and chemical characteristics of the valve components. Whenever valve components are made in conformance with AWWA, ASME, ASTM, or other standards that include test requirements or testing procedures, the manufacturer or supplier shall comply with these requirements or procedures.AWWA C500 pdf download.