抽油杆柱纵向螺旋弯曲对脱扣的影响

抽油杆柱在下行程时,杆柱中和点以下部分受压失稳,发生包括扭转和弯曲在内的空间螺旋弯曲变形。杆柱接头螺纹在失去预紧力和受振动力作用下产生松扣,弯曲变形扭矩则加快了下部接头的脱扣速度。为预防或减少抽油杆柱脱扣,一是减少或避免抽油杆柱发生螺旋弯曲变形,二是上紧接头螺纹,达到要求的上扣预紧力。

Influence of Longitudinal Spiral Bending on Off-Screwing of Sucker Rod Strings,

The rods below the neutral point of a sucker rod string will lack of stability under load on the down-stroke and become deformed spirally due to both twisting and bending. Coupling off-screwing will occur on the lower section of the string under the influence of vibrating force and will be quickened by bending moment. So it is important to make up the rod joints appropriately pretightened and to avoid the spiral bending wherever possible.