By American Water Works Association
Up to date from the 1996 edtion, this operations handbook offers functional info on making a choice on, fitting, box checking out, and conserving distribution valves in potable water platforms. It covers the main established values together with globe, butterfly, plug, ball, cone, gate and payment. Unloading, inspection, garage, set up, trying out, upkeep, and record-keeping are defined intimately in addition to the heritage and thought. This handbook might be fairly usefeul for small and medium sized businesses.
Read Online or Download Distribution Valves: Selection, Installation, Field Testing and Maintenance (M44): AWWA Manual of Water Supply Practice (Manual of Water Supply Practices) PDF
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Extra resources for Distribution Valves: Selection, Installation, Field Testing and Maintenance (M44): AWWA Manual of Water Supply Practice (Manual of Water Supply Practices)
During system operation, small amounts of air enter the valve from the system. As air displaces water within the valve, the water level drops. When the water level falls to the point where the float associated with the valve is no longer buoyant, the float drops. This action opens the valve orifice and allows the air that has accumulated in the upper portion of the valve body to be released into the atmosphere. As this air is released, the water level within the valve rises, lifting the float and closing the valve orifice.
It should be understood and cannot be overstated that to develop a process that is both achievable and beneficial to the effective maintenance and operation of the system is the goal. As the discussion of operation and maintenance ensues, the question arises whether to provide the maintenance of the valve along with its operation or to do 45 46 DISTRIBUTION VALVES them separately. The response is dependent on the manner in which the agency processes its work. Some organizations have crews that operate only, or provide maintenance only, or perform replacements only.
4. When metal-seated gate valves are being used as closure pieces for a test, the test pressure should not exceed twice the rated valve pressure. Metalseated valves have an allowable leakage, and this should be determined before the test. For tests at pressures greater than the rated valve pressure, the test setup should include a reduction of the line pressure to the rated valve pressure (independent of the valve) on completion of the test. The valve can then be opened enough to release trapped pressure and equalize it with the line pressure.