井架不正或井口偏心，会造成近井口套管（或套管防磨套）的磨损。
Both the derrick deviation and the wellhead's eccentricity will cause the serious wearing of the casing (or casing protecting tube) close to the wellhead.
这鞋是由薄鞋底，防磨尼龙弹力面料鞋面，单独的脚趾套，穿上去，就象是一只猩猩的脚。
They are made of a thin, abrasion-resistant polyamide stretch fabric with individual toe slots that look like your foot.
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