AWWA C515-20 pdf download.Reduced-Wall, Resilient-Seated Gate Valves for Water Supply Service
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 likelihood 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 documented that piping system materials, such as polyethylene, polybutylene, polyvinyl chloride, and asbestos cement 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.
Resilient-seated gate valves form a significant component part of many firefighting or water-distribution systems. Failure of a resilient- seated gate valve in these systems, either as a result of faulty installation or improper maintenance, could result in extensive damage and costly repairs. In addition, many resilient-seated gate valves are installed in buried-service or underground applications. Problems or malfunctions of the valves because of faulty installation or improper maintenance can result in extensive and costly unearthing operations to effectively correct or eliminate the problem. Many resilient-seated gate-valve problems and failures can be traced back to improper handling, storage, installation, operation, or maintenance procedures.
Valves should be unloaded carefully. Each valve should be carefully lowered from the truck to the ground; it should not be dropped. In the case of larger valves, forklifts or slings around the body of the valve or under the skids should be used for unloading. Only hoists and slings with adequate load capacity to handle the weight of the valve or valves should be used. Hoists should not be hooked into or chains fastened around yokes, gearing, motors, cylinders, or handwheels. Failure to carefully follow these recommendations is likely to result in damage to the valve.AWWA C515-20 pdf download.