Sumitomo Metals Succeeded in Fracture Arrest Test of
X100 Ultra High Strength Line Pipe - For the First Time in the World

Sumitomo Metal Industries, Ltd. (Sumitomo Metals) has succeeded in a full scale fracture arrest test for the X100(*1) ultra high strength line pipe, which is positioned as the next-generation high strength pipe for gas transmission pipelines. It has been developed to meet the requirements of expanding use and supply of natural gas, a clean form of energy. Up to now, full-scale burst tests of the X100 have not been successful in demonstrating the arrest of ductile running fracture in a high-pressure gas pipeline. Sumitomo Metals' newest full scale test, however, has proved the arrest of running fracture, as predicted by a new simulation model developed by the Company. This has become the world's first successful fracture arrest of the X100 line pipe.

This event raised the reliability of safety performance of the X100 and will promote its commercialization for high pressure gas pipelines. Also, Sumitomo Metals' simulation technology for fracture propagation will become more highly recognized in the world.

1.Traditional experiments on fracture arrest in gas pipeline
A fracture, once initiated in a high-pressure gas pipeline, has the nature of propagating over a long distance in the pipe axial direction. Line pipes for high-pressure gas pipelines are required to have the nature of arresting a fracture, in order to ensure safe and reliable use.

The fracture arrestability, which is represented by the toughness of steel pipe, was evaluated by a test wherein pipes of incremental toughness were aligned, and a fracture was artificially produced. By identifying the pipe where the fracture was arrested, the toughness of fracture arrest pipe, which is a function of the ductility of steel, was measured.

This incremental toughness pipe arrangement test has been successful at the pressure of 7-10MPa with grades up to the X70 line pipe. However, fracture arrest had not been achieved at pressure of over 20MPa with the X100 line pipe. Hence the required toughness for the X100 has not been able to be obtained by this test method.

2.Newly-developed simulation model for fracture arrest and test method
Sumitomo Metals has developed a new simulation model to estimate fracture propagation length in high pressures of over 20MPa. The fracture propagation length varies depending on the toughness of the pipe. Based on this new simulation model, the new test method was applied where the fracture arrest length can be measured by arranging the pipes of the same toughness.

3.Outline of experiment
(1)Execution date: 12 March 2008
(2)Test site: CSM's(*2) test site in Sardinia, Italy
(3)Test conditions
1.Pipe producer: Sumitomo Metals Kashima Steel Works
2.Total length of test line: about 300m
3.Pipe dimensions: OD 914mm (36 inches) and WT 19.05mm
4.Gas temperature: 10 deg C
5.Gas pressure: 22MPa
(4)Test result
The fracture was arrested at about 8-10m away on each side from the initiation point. These results coincide very closely with the simulation results as shown in Figure 1.

4. Achievements of the successful test
The test has proved that the X100 ultra high strength line pipe is capable of conveying natural gas at high operating pressure of over 20MPa, and that fracture arrestability exists even if the fracture is initiated by any chance cause.

This experiment was witnessed by the engineers of leading companies. It has raised reliability of the X100 line pipe. We anticipate that the test will contribute significantly to promote use of natural gas.

By accurately predicting the fracture arrest length by use of the new simulation model, Sumitomo Metals' originality and ability for providing solutions in the field of steel pipe technology for the energy industry are proven and, we believe, merit a high level of appreciation.

5. Future tasks
To contribute to commercialization of the X100 ultra high strength line pipe, Sumitomo Metals are prepared to conduct additional full-scale tests and to provide such data to our customers, in order to gain more confidence in safety of our high strength line pipes.

Notes
*1 X100: Line pipes with a yield strength of 100 kilo pounds or more per square inch
*2 CSM: Centro Sviluppo Materiali S.p.A., Italy's third-party research institute

Figure : Comparison of fracture propagation and arrest between the test results and the prediction based on the simulation model