Maintenance-free directly buried two-way external pressure bellows compensator

The invention discloses a maintenance-free directly buried two-way external pressure bellows compensator, which comprises inner pipes, adapters, thermal insulation material, outer annular plates, an outer pipe, inner annular plates, a flow guide pipe, long bellows, a housing, short bellows, filler and baffles. The two inner pipes are mounted in the hole of the outer pipe, the flow guide pipe is arranged between the two spaced inner pipes, the long bellows, the inner annular plates, the short bellows, the outer annular plates and the adapters are sequentially sleeved and tightly connected with the outer walls of the inner pipes from the inner ends to the outer ends, and thereby an external pressure compensation structure which can move along with the inner pipes is formed. The housing is coaxially sleeved on the outer pipe, and the thermal insulation material is filled up in the gap between the housing and the outer pipe to form a thermal insulation layer. The orifices of the housing are directly sealed by the baffles which are fixedly connected with both ends of the outer pipe, and the holes of the baffles are smaller than the outer diameter of the outer annular plates, so that an axial anti-separation structure for the outer pipe is formed. In order to achieve the purpose of maintenance-freeness in the lifetime, chrome platings are added on the walls of the thin-walled inner pipes and the thin-walled outer pipe, which move relative to each other.