Caterpillar with servo motor realizes precise synchronization driving. With pneumatic flexible clamping, the upper caterpillar can adapt per the pipe specification variation and keeps good contact pressure with the pipe; the lower caterpillar can be electrically adjusted to the required haul-off position per the pipe specification. High friction rubber pads connects with the chain. Haul-off unit with 2, 3, 4, 6, 8 caterpillars