The principle and characteristic principle of rotary compensator is to generate a couple of forces according to the paired rotating cylinder and L moment arm, so that a pair of forces with the same size and opposite orientation can be rotated by the moment arm around the Z axis to manage the center, so as to achieve the digestion and absorption of the thermal expansion amount on the radiator on both sides of the couple. 1. The compensator (rotary compensator) does not cause the introversion working pressure (or the torque of the blind valve), so the support frame on both sides of the compensator can do little. 2, the compensator does not need to empty the warm up when the thermal insulation heat reduction, so the heat damage is small. 3, the compensator (rotary compensator) has a more effective sealing surface structure, and the damage of rubber seals and sealing surface is extremely mild, can not cause leakage in the long term.