Patent ID: 8450631

Claim:
A preserving apparatus for a welded joint portion, for deposit welding on an inner surface of a welded joint portion, in which a nozzle and a pipe supported under water are joined, and preserving the welded joint portion, comprising: a seal member that is disposed in front and behind the welded joint portion to be deposit welded within the nozzle and the pipe, and serves to demarcate and form a closed operation area within the nozzle and the pipe; water drainage means for draining the inside of the operation area demarcated and formed by the seal member and obtaining a gas atmosphere therein; welding means for deposit welding on the inner surface of the welded joint portion within the operation area in which the gas atmosphere has been created; and drying means for drying the welded joint portion prior to deposit welding on the inner surface of the welded joint portion; wherein the seal member has a plurality of nozzle plugs that are inserted, with a predetermined spacing, into the nozzle and the pipe, and a seal tube that is provided so as to expand and contract on the outer periphery of each of the nozzle plugs and serves to seal the space between the nozzle plugs and the inner surfaces of the nozzle and the pipe; the welding means comprises a guide rod that spans between the plurality of nozzle plugs, and a welding torch that is supported on the guide rod so that the welding torch can move freely in the axial direction and radial direction of the guide rod and can rotate freely in the circumferential direction; and the drying means drying the welding surface by inducing an electric arc discharge between the electrode of the welding torch and the welding surface and heating the welding surface by using the arc as a heat source, while controlling the heat input conditions without feeding the filler rod.