Electric heating – Metal heating – Nonatmospheric environment at hot spot
Patent
1986-06-16
1989-05-30
Goldberg, E. A.
Electric heating
Metal heating
Nonatmospheric environment at hot spot
219 74, B23K 916
Patent
active
048353558
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and apparatus for accomplishing an underwater weld joint, preferably for fixing anodes controlling the corrosion of the underwater parts on offshore constructions, in which method the surface of the support to which the element to be welded is to be fastened is first cleaned, after which the welding apparatus is secured to the support for the welding operation. The apparatus comprises cleaning and fastening means for cleaning that surface of the support to which the element is to be welded and for securing the apparatus to the support. The invention also relates to an element to be welded for use with said method and apparatus.
Underwater welding operations have increased intensely owing to the fact that various off-shore constructions have become more common and especially that marine drilling for oil has increased. One of the most significant problems with such off-shore constructions is the attack of corrosion, which, if uncontrolled, will destroy the construction to be useless in a very short time. Attempts have been made to solve this problem, even with good success, by fixing corrosion-controlling anodes onto to the underwater parts. Thereby a new problem has presented itself, the replacement of the corroded anodes with new ones, since underwater welding is very expensive and difficult to carry out.
Known in the art is so-called habitat-chamber welding method used in underwater repair operations which method has also beem used for fixing said corrosion-controlling anodes. This known method is based on supporting the object to be repaired or the corrosion-controlling anode to be fixed into a special chamber wherein the diver carries out the necessary welding operations. Althought said habitat-chamber welding method strives at fulfilling the quality requirements set for the welding by different classification societies, it has the disadvantage of being very expensive both in running cost and in investment, since it employs a large and complicated construction and additionally always requires a diver to be present. Owing to the expensiveness of the habitat-chamber welding method efforts have already long been made to develop wet welding methods wherewith the quality requirements set by the classification societies could be fulfilled. The greatest hindrance to the success of these wet welding methods has been the hardening of the steel in the underwater parts, whereby so-called hydrogen-cracks are formed which may grow with time and break the steel. For this reason, e.g. Det Norske Veritas has prohibited all welding methods not fulfilling the very high requirements for the welding quality set by this classification society.
The object of the present invention is to improve, accelerate and facilitate underwater welding as well as to eliminate the disadvantages and weaknesses of all the previously known underwater welding methods.
These objects have been achieved, according to the method of invention, in such a manner that the element to be welded is brought onto the cleaned support, that the junction of the support and the element to be welded is insulated from the ambient mass of water and that during the welding operation the welding electrode is pressed against the edges of an opening extending through the element to be welded, towards the support.
The apparatus with which this method is carried out is characterized by placing means for bringing the element to be welded to its fastening point on the cleaned support, at least one protecting cover disposed in tight relationship on the free surface of the element to be welded fast at least for the duration of the welding operation, through the wall of the cover at least one welding electrode sealed with respect to said wall extends, the cover insulates the junction between the element to be welded fast and the support from the ambient mass of water, and a drive means for conducting welding current to the welding electrode and for pressing said welding electrode against the edges of the opening in the element during the we
REFERENCES:
patent: 4035602 (1977-07-01), Berghof
patent: 4069408 (1978-01-01), Masubuchi et al.
patent: 4130751 (1978-12-01), Gordon
patent: 4172974 (1979-10-01), Stingelin et al.
Makelainen Hannu
Niinivaara Juhani
Donovan Lincoln
Goldberg E. A.
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