scope:

SCOPE AND DEFINITIONS

General

This Standard covers design, material, manufacturing, testing, marking, and inspection requirements for factorymade pipeline bends of carbon steel materials having controlled chemistry and mechanical properties, produced by the induction bending process, with or without tangents. This Standard covers induction bends for transportation and distribution piping applications (e.g., ASME B31.4 and ASME B31.8). Process and power piping have differing requirements and materials that may not be appropriate for the restrictions and examinations described herein and, therefore, are not included in this Standard.

Manufacturing Process

This process uses induction heating to heat a narrow band 360 deg around a pipe or cylinder at the point of bending as the pipe or cylinder is being pushed through the inductor coil at a constant velocity. After the material passes through the coil, it may be cooled by forced air or water spray, or it may be allowed to cool in still air. Bends in any producible wall thickness and diameter are covered. Induction bends covered by this Standard may be produced from seamless pipe, welded pipe, or cylinders.

Fabricated Bends

Larger angle bends obtained by girth welding two or more smaller angle bends together are considered pipe fabrications and as such, are not within the scope of this Standard.

Standard Units

This Standard states values in both SI (metric) and U.S. Customary units. These systems of units are to be regarded separately as standard. Within the text, the U.S. Customary units are shown in parentheses. The values stated in each system are not exact equivalents; therefore, it is required that each system of units be used independently of the other. Combining values from the two systems constitutes nonconformance with the Standard.

References

Standards and specifications adopted by reference in this Standard are shown in Mandatory Appendix I. It is not practical to identify the specific edition of each standard and specification in the individual references. Instead, the specific edition reference is identified in Mandatory Appendix I. A product made in conformance with a prior edition of reference standards and in all other respects conforming to this Standard will be considered to be in compliance.

Codes and Regulations

A bend used under the jurisdiction of a referencing code or governmental regulation is subject to any limitation of that code or regulation. This includes any maximum temperature limitation or rule governing the use of a material at low temperature.

Service Conditions

Criteria for selection of bend material for a particular fluid service are not within the scope of this Standard.

Convention

For determining conformance with this Standard, the convention for fixing significant digits where limits (maximum and minimum values) are specified shall be as defined in ASTM E29. This requires that an observed or calculated value be rounded off to the nearest unit in the last right-hand digit used for expressing the limit. Decimal values and tolerances do not imply a particular method of measurement.

Quality Systems

Requirements relating to the manufacturers' quality system programs are described in Nonmandatory Appendix A. The Quality System shall specify controls for the manufacturing process, heat treatment process, testing, inspection, material traceability from starting material to final bend, and documentation requirements necessary to ensure compliance with this Standard. The manufacturer shall establish and follow documented procedures for maintaining the heat and lot identity throughout the entire supply chain. Traceability procedures shall provide means for tracing any bend to the proper heat and lot and the chemical and mechanical test results.

Glossary

bend qualification procedure: a document that specifies the properties of the starting pipe; the equipment to be used; the bending parameters; the qualification bend test results; and the postbend, heat-treat equipment, and cycle used for the manufacture of the bends. If nondestructive testing of the bend is required, procedures that have not been approved previously shall be submitted.

cylinder: a joint of pipe produced by a rolling and welding plate, as opposed to a joint of pipe produced in accordance with a recognized specification.

extrados: the outside arc of the bend.

intrados: the inside arc of the bend.

minimum (design) wall thickness: the wall thickness specified or computed in accordance with the piping code as the minimum acceptable for the temperature and pressure application.

nominal (design) wall thickness: the wall thickness specified on the order or marked on the bend.

ovality, %: [(O.D. max. − O.D. min.)/(O.D. nom)] × 100, where O.D. is a linear measurement of the maximum, minimum, or nominal outside diameter.

qualification bend: a bend segment that is produced and tested, and is used to qualify the bending procedure.

transition zone: the area, at the tangent points of a bend, that covers the change (transition) from unheated to heated material.

NOTE: The terms bender and manufacturer are used interchangeably in this Standard.

Ordering Information

The purchaser shall be responsible to specify all the ordering information necessary to purchase the needed bends. Examples of such information include, but are not limited to, the following:

(a) quantity

(b) description of bend and nominal dimensions (i.e., size, bend radius, wall thickness, bend angle, tangent lengths, etc.)

(c) steel composition by grade

(d) seamless or welded

(e) specification number (including year)

(f) supplementary requirements from section SR15

(g) additional requirements

Nonmandatory Appendix B is provided as one possible guideline for providing the required information.