Failure Analysis of Kelly Cock Valve Used in Drilling Process Zheng, Xun ; Deng, Jin Gen ; Zhu, Hai Yan ; Liu, Shu Jie ; Zhao, Wen Long ; Zhang, Mi Hua Abstract Publication: Applied Mechanics and Materials Pub Date: July 2011 DOI: 10.4028/www.scientific.net/AMM.71-78.2610 Bibcode: 2011AMM....71.2610Z