wiggle-spring casing hook
clasp hook [= clip hook
hook and hook turnbuckle
Switchover between one hook and two hook operation
( casing) stress testing tool
a few casing and more circulating
air casing
空气夹层
空气套
空气隔层
气隔套
烟囱外套筒
通风道
[空]气夹层
气套
气夹层
alignment of bottom casing and bearing seating