11MANUFACTURE 11.1 General The following manufacturing standards and rules apply specifically to penstocks and penstock parts that are fabricated by welding and constructed of carbon steel, low-alloy steel, high-alloy steel, or heat-treated steel. 11.1.1 Fabrication Standard Fabrication of penstocks must conform to the provisions of Section VIII, Division 1 of the ASME Code 1 and also the following specific requirements, additional requirements, and the special provisions for spiral seam penstocks given in Section 11.4. IL 233cf resulting in a continuous and uniform curvature using a plate bending roll or a U-ing and forming press. straight-seam or spiral-seam pipe intended for water use. For the pyramid and initial pinch bending rolls the plate edges must be crimped or edge-broken to the proper radius prior to rolling. When carefully evaluated by the engineer.000 psi.11 Manufacture 11. (2) pinch bending rolls. this standard relies on production weld testing and shop hydrostatic testing of each section by stressing the pipe wall to 75% of the specified minimum yield of the steel used. i+ 444 PYRAMID TYPE PINCH TYPE Figure 11-1 Bending Rolls INITIAL PINCH TYPE 0 234 . Figure 11-2 shows U-ing and 0-ing presses used for forming. and pipe fabrication conforming to the ANSI/AWWA C200 standard2 is acceptable. The allowable design stress on these lines usually has been limited to 21. many penstock installations will fall within this service condition.3 Manufacturing Methods 11.1. The ANSI/AWWA standard also covers pipe end preparation and tolerances for field joints.1 Straight Seam Straight-seam penstocks may be shop or field fabricated. including: (1) pyramid bending rolls.2 ANSVAWWA C200 Standard The ANSI/AWWA C200 standard2 covers the manufacture of electrically butt-welded. For quality assurance.3. 11. and (3) initial pinch bending rolls (see Figure 11-1). All plates for shell sections must be formed to the required shape by a process that will not unduly impair the physical properties of the material. Pipe manufactured to this standard has been used primarily in buried lines with O-ring joints to working pressures exceeding 250 psi.1. and bell-and-spigot field-welded and butt-welded joints to working pressures up to 400 psi.1. They are manufactured from plates that are edge-broken (crimped) and then rolled or formed. Several types of bending rolls are available. wall thicknesses through 3/4 inch are available. Penstock courses must be assembled with the longitudinal seams staggered a minimum of 15 degrees.11 Manufacture U-shape plate Q U-ING PRESS Figure 11-2 FormingPresses Cylindrical pipe 0-ING PRESS Plates for penstock shells must be sized to minimize the number of longitudinal and circumferential seams inthe completed section. Currently. Exterior weld + I Figure 11-3 Process for Making Spiral-Seam Pipe LU 235 . The diameter of the penstock is determined by the angle of the coil feed to the axis of the penstock in relation to the width of the coil (see Figure 11-3).3.2 Spiral Seam Spiral-seam penstocks are manufactured in the shop using steel in coiled form.1. the coil is unrolled. 11. . and the coil is helically formed to a true circular shape and welded in a continuous operation. the coil edges are prepared as required. In this process. The penstock is cut to length as required by an automatic cut-off device. Division 1. 11.1. Section VIII. No production welding can be undertaken until the welding procedures have been qualified. such as supports.1.2 Material for Nonpressure Parts Material for nonpressure parts. need not conform to the specifications for the material to which they are attached or to the material specifications described in Sections 2.11 Manufacture Pipe ends for the required field joints may need expansion or sizing to meet the tolerances specified in Section 11. Part UW. thrust rings. 11. However.2 Welding Welding of shells and assemblies classified as pressure parts must be in accordance with the ASME Code.5. Fabrication in accordance with the ASME Code may not be required for low-head or nontraditional penstocks. 11. and clips.5. as well as an internal quality control system similar to the SPFA Plant Quality Certification Program. lugs.3.2 Qualification of Manufacturer The manufacturer must demonstrate that it has the shop facilities and also has had fabrication experience with specialty work of similar size and type within the past 5 years.3 Manufacturing Specifications Fabrication of the penstock and penstock parts must be performed in accordance with the provisions of the ASME Code.4 or 2. 0 Mi 236 .1 Material for Pressure Parts Material subject to stress due to pressure must conform to one of the specifications given in Section 2. Only welders and welding operators who have been qualified in accordance with Section IXof the ASME Code 6 can be used in production.3. Division 1. they must be of weldable quality.3. However.3.3. The welding processes used in the construction of penstocks are restricted to those outlined in Section 11.3 11. 11.3.1. The fabricator is not required to stamp any part of the penstock with the official ASME Code symbol applicable to pressure vessels.1 Material Materials used for steel penstocks and penstock parts must be furnished in strict accordance with the proper ASTM standard and specifically in accordance with the requirements of ASTM 4 designations A6 and A20 5 as appropriate. 11.2.1 Section VIII. ifnonpressure parts are attached to the penstock by welding.3. hydrostatic testing is not mandatory.4 and 2.1. 11 Manufacture 11. The procedure specification for the material being welded specifies the minimum preheating temperature under the weld procedure qualification requirements of Section IXof the ASME Code. A metallurgical or welding engineer should be consulted about mandatory or recommended preheat requirements.3 Field Joint Ends Ends of supplied penstock sections must be of the type specified by the purchaser.3. including conditions for postweld heat treatment.3. UHA-32. and UHT-56) when the nominal thickness of any welded joint in the penstock section or part exceeds the limits in those tables.2 Welding Materials Welding materials used for production must comply with the requirements of the ASME Code. 11. UCS-56. and gas tungsten arc (GTAW). Edges of plates prepared for welding must be examined visually for signs of lamination.1 Section VIII.4 Preheating The minimum preheating temperature for all welded joints is 50°F (mandatory).and the applicable welding procedure specification.3 Edge Preparation Shell plate edges must be prepared for welding as required by the applicable welding procedure specification. 11.3. Appendix R of Section VIII.2. Defects must be removed by mechanical means or by thermal gouging processes.1. Section VIII.3. All penstock sections and parts must be given a postweld heat treatment at temperatures not less than those specified in the ASME Code. ANSI/AWWA C2002 describes the following types of ends: (1) Plain-end pipe (2) Beveled ends for field butt welding (3) Ends fitted with flanges (4) Ends fitted with butt straps for field welding L23 237 C .5 Postweld Heat Treatment 6 Weld procedures must conform to Section IXof the ASME Code. 11.2.2. submerged arc (SAW). also should be reviewed. flux cored arc (FCAW).2. gas metal arc (GMAW). 11.2.1 Welding Process Arc-welding and gas-welding processes are restricted to shielded metal arc (SMAW). Division 1. 11. The nonmandatory guidelines of the ASME Code. shearing cracks.3. and other imperfections. and Section IX.3. Division 1 (Tables UCS-56. based on circumferential measurement (7D). Inaddition. (2) Outside diameter The outside diameter tolerance. 11.1 Manufacturing Tolerances at Ends (1) Out-of-roundness The difference between the major and minor outside penstock shell diameters must not exceed 1%.3. (3) Squareness of ends for butt welding Ends of penstock sections must not vary by more than 1/16 inch at any point from a plane normal to the longitudinal axis and passing through the center of the section at the end. the penstock shell must meet the requirements of UG-80(b) of the ASME Code. Division 1.4.3.4 Tolerances 11.3.3. with regard to plus-or-minus deviation from true circular form.1 Out-of-Roundness The difference between the major and minor outside diameters must not exceed 1%. 238 . 11.1 Section VIII. the penstock shell must meet the requirements of UG-80(b) of the ASME Code 1 Section VIII. In addition. is ±1/4 inch for the following: (a) Plain-end pipe (b) Beveled ends for field butt welding (c) Ends fitted with flanges (d) Ends fitted with butt straps for field welding (e) Ends for mechanical couplings (must have tolerances within the limits required by the coupling manufacturer) (f) Lap joints for field welding (circumferential difference between inside of bell and outside of spigot must not exceed 2/5 inch).11 Manufacture (5) Ends for mechanical couplings (6) Lap-joint pipe ends for field welding (7) Bell-and-spigot ends with rubber gaskets. Division 1 with regard to plus-or-minus deviation from true circular form. based on circumferential measurement (n[D).2. The forming process must be continuous.4.1 Steel Coil Steel coils must be con-cast killed steel.35%.3 Tolerances The mandatory pipe barrel circumference tolerance is ±0. 11.1.4. 11.4. if necessary. alignment cannot exceed 1/8 inch. 11. but cannot exceed ±3/4 inch from the nominal outside circumference based on the diameter specified. All other tolerances must conform to those specified in Section 11.3.3. including physical tests as supplemented by Section 2.4 Length Lengths must be within ±1/2 inch of the specified length unless otherwise agreed upon by the manufacturer and purchaser. with the exception of the following special provisions.2 Forming The spiral-seam manufacturing process must be set up to the correct feed angle for the coil width used and the penstock diameter required.3. with fine austenitic grain size.3.4 Supplemental Requirements for Spiral-Seam Penstocks Spiral seam penstocks generally are manufactured in accordance with ANSI/AWWA C200 2 and ASTM Al 397 standards.5 Minimum Wall Thickness The wall thickness (in inches) at any point in the penstock must not be less than the specified nominal thickness minus 1/100 inch.11 Manufacture 11. to meet field joint tolerances required by Section 11. The initial start-up section up to the point at which diameter control has been obtained must be discarded. Spiral-seam pipe for traditional penstocks must be manufactured in accordance with the requirements of Section 11.3. 11.3.4. is ±1/4 inch.5. and must conform to one of the specifications given in Sections 2.2 Outside Diameter The outside diameter tolerance. L23 239 .3.4 and 2.3 Alignment Using a 10-foot straight edge placed so that the ends are in contact with the pipe. 11.4.4.3. 11.2. Pipe ends must be sized.4. 11.4. 4. Some manufacturers offer 100% continuous and uninterrupted ultrasonic inspection of helical weld seam and skelp-end weld seam in accordance with methods and acceptance criteria outlined in API Specification 5L. consideration must be given to weld inspection beyond the requirement of the manufacturing standards.8 coupled with shop hydrostatic testing of all penstock sections at 75% of the material yield strength.11 Manufacture 11.4 Weld Inspection When design stresses exceed 21. 0 hi 240 .000 psi. Steel Plate Fabricators Association. Denver. ASME Boiler and Pressure Vessel Code. code. ASTM. PA.ASME. 2. 241 .. ANSI/AWWA Standard C200. * The most current version of a standard. Division 1. and Bars for Structural Use. ASME. 6. Westchester. 4. DC. Section IX. Brazers. SPFA Plant Quality Certification Program. ASTM Designation A6. Specification for Line Pipe. ASTM Designation A20. Standard Specification for Electric-Fusion (Arc) Welded Steel Pipe (NPS 4 and Over). and Welding And Brazing Operators. 8. Shapes. 7. 5. Philadelphia. Standard Specification for General Requirements for Steel Plates for Pressure Vessels. NY. Washington. PA. PA. 3. ASTM Designation Al 39. Standard Specification for General Requirements for Rolled Steel Plates. NY. Section VIII. Inc. ASTM. American Petroleum Institute. Welders. New York.I References* 11 Manufacture 1. Sheet Piling. Philadelphia. CO. Philadelphia. API Specification 5L. Qualification Standard for Welding and Brazing Procedures. AWWA. New York. Steel Water Pipe 6 Inches and Larger. ASTM. IL. or specification should be used for reference. ASME Boiler and Pressure Vessel Code. Rules for Construction of Pressure Vessels.