Air Valve Sizing and Location: A Prospective

This paper critically assesses the design approach presented in the American Water Works Association M51 manual of practice, entitled "Air-Release, Air/Vacuum, & Combination Air Valves." The design approach presented in this manual of practice is widely used in potable water system pipeline design for both sizing and locating air valves. The recommended design approach has been evaluated and an alternative approach is proposed. The current M51 recommended design approach introduces a very broad range of design criteria in regards to sizing and locating air valves in a pipeline system. This approach does consider different loading conditions, but does not consider that during the life of the pipeline all these different loading conditions may be experienced. Therefore, the author proposes that a more careful and more rigorous method be used to size and locate air valves. The proposed method considers the air valve's primary modes of operation, the air valve's performance under dynamic loading conditions, and the use of a fully dynamic hydraulic model to assess the air valve sizing and location. The paper introduces a hypothetical case where the M51 design approach is utilized and the results of M51 design are compared to the design approach utilizing the more rigorous method. In summary, to meet all the established criteria, the sizing of the air valve(s) for air release and surge control is decreased but to accommodate the uncontrolled drainage mode of operation an additional air valve was required.