六是塔筒结构为防止平衡重自由落体坠落提供了理想的支撑载体，确保了失载保护的万无一失。

The tower tube structure to prevent counterbalance freefall provides ideal support, to ensure that the load loss protection is on the safe side.

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平衡重设置自由落体紧急制动装置，可实现井口端意外失载后平衡重自由落体坠落不能人控，却能自控失载保护的万无一失。

Balance weight set free fall emergency braking device, which can realize auto control load loss protection, when the wellhead end accidental loss of load, balance weight free fall.

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