基于超声波测厚的海洋修井机井架强度分析

Finite Element Strength Analysis for Mast of Offshore Workover Rig based on Ultrasonic Thickness Measurement

为评估在役井架的承载能力,采用超声波测厚仪,在海上平台现场对服役8 a的HXJJ180井架杆件厚度进行了测量,据此建立了井架有限元模型,并按16种组合工况对井架进行了强度分析。由于井架各杆件不仅承受轴向力,而且也承受弯矩作用,故单元类型选择时考虑了结构尺寸和承受的载荷;将井架下底座视为刚体,约束连接处的所有自由度。分析结果表明,海洋修井机井架受环境腐蚀较为严重,有限元分析有助于掌握各杆件在给定工况下的应力及强度特性,采用超声波测量方法可获得精确的杆件厚度数据,保证有限元模型与实际井架相符;井架在最大钩载下最大应力小于许用应力,仍可安全服役,但最大应力200.41 MPa接近许用应力,使用中应避免过载,并注意防腐,以延长井架服役寿命。

To evaluate the bearing capability of in-service mast, the ultrasonic thickness meter is adopted to measure thickness of members of HXJJ180 mast which had been in service for 8 years on the offshore platform, and a finite element model of mast is established. In addition, strength of mast is analyzed under 16 combinations of working conditions. Since all members of the mast sustains not only axial force, but also bending moment, structur- al size and possible load are taken into consideration in selection of unit. The lower base of the mast is regarded as a rigid body to restrain degree of freedom of connection points. The analysis results show that the offshore workover rig is severely corroded by environment, whereas the finite element analysis is favorable to understand stress and strength characteristics of all members under given working conditions, and precise member thickness data can be obtained by adopting the ultrasonic wave measurement method, so as to guarantee that the finite element model is consistent with actual mast. The maximum stress of mast under the maximum hook load is smaller than allowable stress, and it is still able to be in service. However, the maximum stress 200. 41 MPa closes to the allowable stress, so overloading shall be avoided during the operation. Moreover, corrosion should be avoided to extent the service life of the mast.