Abstract

The results of an investigation of a long-seam welded low chrome pipe that failed in a high-temperature refinery piping system are presented in this paper. Based upon the results of a metallurgical investigation, which included a creep testing program and a detailed finite element stress analysis, the cause of the failure has been attributed to creep damage at the weld seam. The metallurgical investigation and creep testing program indicated that the 1-1/4 Cr-1/2 Mo pipe material was normalized and exhibited greater than average creep strength and creep ductility. The results of a piping stress analysis indicated that all pressure, weight, and thermal stresses were in compliance with the ASME B31.3 Piping Code (ASME, 1993a). Nonetheless, the pipe failed after only 100,000 h at a nominal hoop stress of 6 ksi (41.4 MPa) with an operating temperature range of 970°F (521°C) to 1000°F (538°C). Results from subsequent detailed finite element stress analyses of the failed pipe indicated that very high localized bending stresses were present in the pipe due to peaking at the long-seam weld. These stresses partially relax by creep, but after 100,000 h they were still approximately 38 percent higher than the nominal hoop stress. The creep strains resulting from stress relaxation and those associated with the long-term value of the sustained stresses cause severe creep damage at the weld seam. As a result of this damage, cracks initiated at the inside of the pipe and primarily grew through the HAZ/fusion line until an 18-in. through-wall crack developed. The pipe was produced to ASTM A691, Grade 1-1/4 Cr, Class 41 (ASTM, 1989), and the peaked geometry was found to satisfy the fabrication tolerances of this standard. The need for the development of an acceptable tolerance for peaking in addition to the outside diameter and out-of-roundness fabrication tolerances currently included in this standard is highlighted for long-seam welded pipe that is to operate in the creep range.

Issue Section:
Research Papers
Topics:
Failure, High temperature, Petroleum refinery piping, Pipes, Creep, Damage, Stress, Stress analysis (Engineering), ASTM International, Finite element analysis, Fracture (Materials), Hoop stress, Manufacturing, Testing, Bending (Stress), Ductility, Geometry, Operating temperature, Pressure, Relaxation (Physics), Thermal stresses, Weight (Mass)
1.
ASME, 1993a, ASME B31.3, Chemical Plant And Petroleum Refinery Piping Code, The American Society of Mechanical Engineers.
2.
ASME, 1993b, ASME Boiler and Pressure Vessel Code, Section II - “Materials,” Part D - “Properties,” The American Society of Mechanical Engineers.
3.
ASME, 1993c, ASME Boiler and Pressure Vessel Code, Section III, Code Case N-47, The American Society of Mechanical Engineers.
4.
ASTM, 1989, “ASTM A691, Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-Pressure Service at High Temperatures,” 1989 Annual Book of ASTM Standards, Section 1, Iron and Steel Products, Vol. 01.01, Steel-Piping, Tubing, Fittings, American Society for Testing and Materials, pp. 539–543.
5.
Wells, C. H., and Viswanathan, R., 1993, “Life Assessment of High Energy Piping,” Technology for the 90s, American Society of Mechanical Engineers, Chap. 6, pp. 179–216.
6.
MPC, 1989, oral presentations at the Materials Properties Council TAC Meeting, Orlando, FL, Nov.
7.
EPRI, 1987, “Guidelines for the Evaluation of Seam-Welded Steam Pipe,” ERPI Report CS-4774, Research Project 2596–7, Feb.
8.
Osage, D. A., and Cacciatore, P. J., 1986, “Improved Reliability Of High Temperature Cyclic Piping Systems Through State-Of-The-Art Design And Analysis,” 1986 Proceedings—Refining Department, 51st Midyear Meeting, San Diego, CA, May 12–15, Vol. 65, American Petroleum Institute, pp. 665–677.
9.
MPC, 1993a, “Report to API on Program on Prevention and Repair of Cracking in Cr-Mo Equipment,” The Materials Properties Council, Sept.
10.
MPC, 1993b, “Development of Systematic Procedures for Evaluation of Welded Steam Piping in Creep Service,” Request for Proposal 93-11, The Materials Properties Council, Aug.
11.
Prager, M., 1994, “Development of the MPC Method for Life Assessment in the Creep Range,” Service Experience and Reliability Improvement—Nuclear, Fossil and Petrochemical Plants, ASME PVP-Vol. 288, American Society of Mechanical Engineers, pp. 401–421.
12.
ASTM, 1973, Evaluation of the Elevated Temperature Tensile and Creep-Rupture Properties of 1/2 Cr-1/2 Mo, 1 Cr-1/2 Mo, and 1 1/4 Cr-1/2 Mo-Si Steels, Data Series DS 50, American Society for Testing and Materials.
13.
Hibbet, Karlsson & Sorensen, Inc., 1993a, ABAQUS User’s Manual.
14.
Hibbet, Karlsson & Sorensen, Inc., 1993b, ABAQUS Theory Manual, pp. 4.5.7-1–4.5.7-2.
15.
Krauss, H., 1980, Creep Analysis, John Wiley & Sons, Inc., pp. 18–27.
16.
Tu, S. T., Segle, P. M., and Samuelson, L. A., 1993, “Some Aspects of the Design of Welded Structures Subjected to High Temperature Creep,” High-Temperature Service and Time-Dependent Failure, PVP-Vol. 262, ASME, pp. 27–34.
17.
Liaw
P. K.
,
Saxena
A.
, and
Schaefer
J.
,
1989
, “
Estimating Remaining Life of Elevated-Temperature Steam Pipes—Part II, Fracture Mechanics Analyses
,”
Engineering Fracture Mechanics
, Vol.
32
, No.
5
, pp.
709
–
722
.
18.
Bloom, J. M., 1993, “Validation of Creep Crack Growth Life estimation Methodology/Hot Reheat Steam Pipes,” High-Temperature Service and Time-Dependent Failure, ASME PVP-Vol. 262, pp. 181–185.
19.
Wells, C. H., 1994, private communication, March 18.
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