ASCE MOP 79

Abstract

<strong>PREFACE</strong> <br>This <em>Manual of Practice for Steel Penstocks</em> covers the design, manufacture, installation, testing, startup, and maintenance of steel penstocks, including branches, wyes, associated appurtenances, and tunnel liners. Standards presented in this manual are applicable only to steel penstocks. As used in the manual, a penstock is defi ned as a closed water conduit located between the fi rst free water surface and a hydroelectric power station. <br>The <em>Manual of Practice for Steel Penstocks</em> was fi rst published in 1993. This 2012 edition is an update of that publication. This update was prepared by a special ASCE task committee under the supervision of the ASCE Pipeline Division with assistance from the ASCE Energy Division. The task committee was charged with updating the manual to match current practice, codes, and standards. <br>In 1985, the <em>Hydropower</em> Committee began work on the <em>Civil Engineering Guidelines for Planning and Designing Hydroelectric Developments</em>, commonly referred to as the <em>Guides</em>. Upon the work's completion, the committee decided to expand the section on penstocks into a nationally accepted standard or code. <br>The penstock design documents most commonly used by the penstock industry are the ASME Boiler and Pressure Vessel Code (ASME Code) and the AISI Steel Plate Engineering Data&#8212;Volume 4, Buried Steel Penstocks. <br>The ASME Code has been in existence since 1914 and originally was based on an allowable stress of one-fi fth the tensile strength of the steel. An ASME Code section specifi cally for pressure vessels came out in the mid-1920s. In the 1950s, the stress basis was changed to one-fourth of the tensile strength of the steel. The high-stress alternative rules, based on one-third of the tensile strength of the steel, came out in the 1960s, although the theory and stress basis had been in use for some time before that. Fabrication based on these rules has resulted in high-quality structures. The rules for both divisions of Section VIII of the ASME Code are accepted worldwide and have been applied to many types of structures other than pressure vessels, including penstocks. The alternative rules of Section VIII, Divisions 1 and 2, have been used extensively in preparing this manual. <br>The development of Volume 4 was based primarily on the 40-plus years of laboratory research and practical hydroelectric experience of the U.S. Bureau of Reclamation. The manual provides more specifi c penstock design information than the ASME Code but refers to the latter for fabrication and welding. <br>Although the procedures outlined in this manual are intended to be clear enough for the inexperienced engineer, many of the decisions on methodology of design and safety factors should be discussed and decided with the aid of an experienced design engineer. Avoiding risk requires a knowledge of diameter, pressure, potential consequence, and many other factors. Proper design of penstocks requires a certain amount of experience. <br>The design procedures presented in this document are recommended by the task committee. However, the committee recognizes that there are other methods and procedures that may be equally valid. This document does not preclude their use, provided the engineer is satisfi ed with their validity and applicability.