Study on structural strength of carbon steel pipes in applying ice plugging procedure

In in-service plant pipings, a procedure called 'ice plugging' or 'freezing' is practical for purposes of maintenance or pressure testing. The concept of the procedure is the formation of internal ice plug to temporarily block water filled pipes. In this research, two types of test were conducted to assess the applicability of this procedure especially for carbon steel piping. In the material property tests, no differences of properties were found between the conditions as received and after low temperature holding in typical carbon steelpipe material, STPT42 (JIS G3456). In the mock-up tests, unnotched and notched pipes (STPT42, nominal dia. 40A) were subjected at -80degC, and reliable ice plugging performance and no permanent pipe damage were resultantly comfirmed. (author)