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| Failure Analysis on Deflated Ball Valve of Natural Gas Pipeline |
| Received:August 17, 2017 Revised:December 15, 2017 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/ issn.1672-9242.2017.12.002 |
| KeyWord:natural gas ball valve rupture failure analysis |
| Author | Institution |
| FU An-qing |
State Key Laboratory of Performance and Structural Safety for Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| REN Yue-fei |
The Third Gas Recovery Plant of Chang-qing Oilfield Branch, Xi'an , China |
| LAI Wei-ya |
State Key Laboratory of Performance and Structural Safety for Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| XU Xiu-qing |
State Key Laboratory of Performance and Structural Safety for Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
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| Abstract: |
| Objective To analyze causes of the leakage for rupture on ball valve of gas pipeline at a western natural gas field. Methods Chemical composition, fracture and microstructure of the ball valve were analyzed. Results The ball valve cracks originated from the body surface. The cracks extended along the grain boundary. Poor chromium phenomena were not detected in grain boundary and there was no intergranular corrosion. Dendrite and casting defects along grain boundary were found in the material. Micro-cracks formed along grain boundary in the process of water quenching. Cracks propagation was along the grain boundary under pressure. Thread root was the thinnest part and could produce stress concentration. Cracks extended outward and eventually ruptured along the thread root. The fracture morphology was the intergranular brittle fracture. Conclusion The reasons for ball valve failure are the stress concentration in thread root and defects in casting body. Under the effect of both, the intergranular brittle fracture occurs to the valve body under pressure condition. |
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