Study on External Collapse Resistance of Φ139.7 mm×12.7 mm CB125HC High Anti-collapse Casing

Studied via the physical testing and the FE simulation is the effect of the geometrical parameters on the collapse resistance of the high anti-collapse casing. The geometric parameters like OD and WT of three pieces of the Φ139.7 mm×12.7 mm CB125HC casings of the same batch are inspected. And the collapse test is also conducted with the vertical collapse testing system to the said casings，and thus the anti-collapse strength thereof are obtained. The geometric parameters resulted from the inspections and result from the collapse test are analyzed so as to investigate the effects by the wall thickness unevenness and the ovality on the collapse resistance of the casing. The FE model is set up with the data as actually measured to calculate the collapse strength values of each specimen which are then compared with relevant API calculation values and the measured values as well. As a result it is shown that the collapse resistance of the high anti-collapse casing is far higher than the API calculation value，which means that the API-specified formula is not applicable to the high anti-collapse casing，and that the FE result is close to the testing result. So it is concluded that the above mentioned FE method is capable of quickly predicting the collapse resistance of the high anti-collapse casing.