Reasons Analysis on Galling of φ177.8 mm Buttress Thread Casings

In order to find out the galling reasons of φ177.8 mm buttress thread casings in one oil field, the making up and breaking out test was done to the casing samples. The test results show that the casing galling was because there was quality problem on the casing thread connection. By analyzing the related standard and the making up and breaking out test program constituted by the mill, it was found that the casing galling problem could not be found by the existing test methods because there was difference in threading between specimens for test and products. The improved making up and breaking out test method was suggested.