Investigating the Changes of Mechanical and Metallurgical Properties Obtained by Hydrostatic Test Using the Method of 110% Yield Stress in Gas Pipelines

One of the questions that exist for operators is the effect of 110% pressure of the hydrostatic test on the mechanical and metallurgical properties of the pipe and its effects during operation. The purpose of this article is to examine this issue through practical tests and theoretical and software analysis. In order to achieve this goal, a 110% hydrostatic resistance test (in cooperation with the research unit of Iran Gas Engineering and Development Company at the Bandar Abbas site) was conducted on a 30-inch pipe (API5L PIPE30 THK0.5 SAW X60) and since the pipe was under 4 hours the pressure was applied and the results obtained are the same as the actual conditions.
A 30 cm ring was cut from the above-selected pipe before applying the resistance pressure and a 30 cm ring was cut from the pipe after the resistance test
With the aim of obtaining reliable results and data, mechanical bending, tensile and impact tests in the reference laboratory of Arak Gam, which has a certificate from the standards department, and hardness and metallography tests in the metallurgy laboratory of the quality control unit of Arak Machinery Company (QA) Done.
By obtaining the X60 pipe stress strain diagram and properties in the plastic area from the tensile test, the pipe under 110%Sy pressure was analyzed in Abaqus software and the plastic stress and strain created in the pipe was analyzed and the thickness of the elastic and plastic areas was estimated with the help of Abaqus. was hit.
In order to investigate the possible changes in the metallurgical structure, samples before and after the strength test were examined in macro and micro mode in cooperation with the quality control laboratory of Arak Machinsazy Company.