WO1985002801A1

WO1985002801A1 - Method of underwater welding

Info

Publication number: WO1985002801A1
Application number: PCT/FI1984/000101
Authority: WO
Inventors: Kalervo M. A. KYYTSÖNEN
Original assignee: Subsea Welding & Engineering Limited
Priority date: 1983-12-22
Filing date: 1984-12-27
Publication date: 1985-07-04
Also published as: EP0165983A1; AU3832385A; FI834751A0

Abstract

A method for carrying out underwater welding, according to which method the area to be welded is covered by means of a watertight structure (1), in whose interior the welding is performed. According to the invention, a bottomless box-shaped local chamber (1) is used as the watertight structure, into which said chamber sealing and insulating material (11) is fed so that water cannot penetrate to the interior of the edges of the chamber (1) and which chamber is shifted forwards at the same rate as the welding makes progress. An animal-fat based pasty material is preferably used as the sealing and insulating material (11).

Description

Method of underwater welding

The present invention concerns a method of underwater welding in accordance with the preamble of claim 1. According to the method, the area to be welded is protected so that the weld area and the seam freshly welded become insulated from the effects of water. Such a procedure is also called local chamber method. On the basis of the Finnish Announcement

Publication No. 64,903, it is known, in underwater arc welding, to apply a semisolid or solid pasty material to the area of the arc, which material, forming an electrolyte, is at least partly soluble in water. On the basis of the said cited publication, materials known in prior art are, e.g., certain salts of an organic or inorganic acid, alkali salts of fatty acids, as well as soap or soft soap.

On the basis of the Finnish published Patent Application No. 780283, it is known to feed a mix or paste to the welding area out of a nozzle placed in the immediate proximity of the arc. In such a case, among other things, the piece of mix or paste is fitted so that the arc burns in a cavity formed into the said material. When the welding makes progress, a protective layer is deposited out of the piece of material onto the weld.

On the other hand, out of the Finnish pub¬ lished Patent Application No. 802244, a protective paste used in underwater arc welding is known, which paste consists, among other things, of a base sub¬ stance which is mixed in glycerine and contains 40 to 60 per cent by weight of oleic acid, 1 to 40 per cent by weight of linoleic acid, 8 to 21 per cent by weight of stearic acid, 20 to 30 per cent by weight of palmitic acid, as well as 1 to 4 per cent by weight of myristinic acid. By means of the prior-art methods and materi¬ als described above, quite good results have been obtained in underwater arc welding. These have, how¬ ever, not provided such a protection from the effects of water that they were usable in off-shore industry. The object of the present invention is to eliminate the drawbacks occurring in the prior-art technique described above and to provide a method that protects the area to be welded and the welded joint seam from the effects of water more efficiently than in prior art.

The method in accordance with the present invention- is based thereon that the area to be welded is covered by means of a bottomless displaceable box- shaped chamber structure, which is filled with a sealing and insulating material that, when the welding makes progress, all the time prevents penetration of water into the effective range of the chamber.

More specifically, the method in accordance with the invention is mainly characterized in what is stated in the characterizing portion of claim 1.

According to the invention, preferably animal fat is used as the sealing and insulating material, in particular bovine or pork fat or combinations of same. Such a sealing and insulating material advantageously contains at least 30 and preferably at least 60 per cent by weight of animal fat. Pure animal fat has proved the most efficient protective material, which is characterized in that it is insoluble in water. The animal fat is most appropriately bovine or pork fat, or a mixture of same. Thus, in relatively warm waters (above 15°C), it is possible to use, e.g., pure bovine fat, which has a higher viscosity than pork fat has. In colder waters, the proportion of pork fat should preferably be increased. Thus, good results have been obtained with a mixing ratio 50/50 of bovine fat to pork fat. The invention will be examined in the following in more detail with the aid of the exempli¬ fying embodiment in accordance with the attached drawing, illustrating the local chamber method. Figure 1 is a partly sche atical view of one equipment used in the method of the invention.

Figure 2 is a partly schematical view of a second equipment used in the method of the invention. It comes out from Fig. 1 how the sealing and insulating material can be fed in accordance with the invention into the local chamber in underwater arc welding.

When welding by the local chamber method, the welder-diver works completely under the same sort of conditions as when performing wet welding. The difference lies therein that the arc area and the weld seam are protected and insulated from the effect of water by means of the local chamber. Such a local chamber is provided by means of a device that is shaped such that the welder-diver can readily carry it when the welding makes progress so that the welding rod burns inside the local chamber 1.

The local chamber 1 is box-shaped and open at the bottom (rectangular opening) , and the sealing and insulating material 11 can be fed through its top portion through a hose 3 out of a feeder device 4 to 6, which, in the example case, comprises a hydraulic cylinder 6 and a cylindrical feeding container 4. The piston 5 presses material 11 into the hose 3. The hydraulic cylinder 6 is controlled by means of a trigger 8 fitted on the tube 2 connecting the hose 3 with the local chamber 1, and the actuating impulse of the said trigger makes, by the intermediate of the control device 7, the cylinder 6 feed new material 11 into the hose 3. The feed can also be arranged so that it takes place, e.g., by means of compressed air. The front portion of the box-shaped local chamber 1 is provided with an opening 9, through which the welding rod 10 can be fitted into the chamber 1. The opening 9 has preferably the shape of an inverted letter U or -V.

Thus, sealing and insulating material 11 is fed out of the container 4 into the local chamber 1 so that it seals the effective range of the chamber against the effect of water. When the chamber 1 moves forwards as the welding makes progress, a layer 12 of sealing and insulating material remains within the effective range of the chamber, whereby the water cannot act upon the weld seam immediately after the chamber has moved beyond the seam. After the welding of the seam has been completed, the welder-diver removes the material. By means of the trigger 8 mentioned above, the welder-diver can regulate the quantity of the material 11 as required. Sealing and insulating mate¬ rial 11 must be supplied at least so much that at least the edges of the chamber 1 are covered by the material 11 inside the chamber 1.

The construction shown in Fig. 2 differs from that shown in Fig. 1 in the respect that the welding electrode 10 (which may also be, e.g., a wire-shaped structure unwound off a roll) penetrates into the chamber through an opening 9* placed in the top face of the local chamber 1. It is an advantage of this solution that the moving of the local chamber 1 and of the welding rod 10 may take place as one unit by one hand. Since the mouthpiece 1 has no notch, after it, no material layer 12 of the sort shown in Fig. 1 remains after it on the weld.

If necessary, the shape of the local chamber can, of course, be varied depending on the shape of the object to be welded.

By means of the local chamber method, a definitely watertight environment is obtained for the welding area and detrimental effects of water are ex¬ cluded. As regards its properties, the welding result obtained by this method equals a weld performed in an atmospheric environment. The composition of the. sealing and insulating material has a decisive importance for the generation of optimal watertightness of the local chamber. Since underwater welding must be carried out both in tropical waters and in arctic waters, by changing the mixing ratio of the material it is possible to obtain the optimal viscosity for the material, required by the change in temperature, as came out above.

The following table, shows typical analyses of bovine and pork fat, which analyses were performed at the Finnish State Inspection Centre for Dairy Products.

TABLE

The numbers in the first column mean

Number of carbon atoms : Number of double bonds in the fatty acid chain It should be noticed that, within the scope of the following patent claims, e.g., bovine and pork fat also means processed modifications of these fats and combinations of such modifications. The bovine and pork fats, are definable in accordance with the following code: (Joint FAO/WHO Food Standard Program; Codex Alimentarius Commission) :

Bovine fat Pork fat -Premier .Jus -Lard

CAC/RS 30-1969 CAC/RS 28-1969

-Edible Tallow -Rended Pork Fat

CAC/RS 31-1969 CAC/RS 29-1969

Into the sealing and insulating material, e.g., fluorine compounds may be mixed in order to prevent absorption of hydrogen into metal. Such fluorine compounds are, e.g., CaF-,, CF., C.Fg, CdFg, and XeF-,. The proportion of these additives in the total quantity is preferably less than 40 per cent.

Even though, in the exemplifying embodiment described above, the local chamber method is described as applied in connection with arc welding, it should be noticed that the local chamber in accordance with the invention is also suitable for being used in con¬ nection with other types of welding.

Claims

WHAT IS CLAIMED IS:

1. Method for carrying out underwater welding, according to which method the area to be welded is covered by means of a watertight structure (1), in whose interior the welding is performed, c h a r a c t e r i z e d in that a bottomless box- shaped local chamber (1) is used as the watertight structure, into which said chamber sealing and insu- lating material (11) is fed so that water cannot penetrate to the interior of the edges of the chamber (1) and which chamber is shifted forwards at the same rate as the welding makes progress, whereby the tip of the welding member (10) penetrating into the chamber (1) is constantly surrounded by the sealing and insulating material (11) present in the chamber (1)

2. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that a structure (1) is used as the local chamber whose walls define an at least sub- stantially rectangular area around the area to be welded.

3. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that a pasty material containing at least 30 and preferably at least 60 per cent by weight of animal fat is used as the sealing and insulating material (11).

4. Method as claimed in claim 3, c h a r ¬ a c t e r i z e d in that bovine fat is used as the animal fat.

5. Method as claimed in claim 3, c h a r ¬ a c t e r i z e d in that pork fat is used as the animal fat.

6. Method as claimed in claim 3, c h a r ¬ a c t e r i z e d in that a mixture of bovine fat and pork fat is used as the animal fat (11) .

7. Method as claimed in claim 6, c h a r ¬ a c t e r i z e d in that a mixture (11) is used in which the proportions of bovine fat and pork fat are at least almost equally large.

8. Method as claimed in claim 1, c h a r -, a c t e r i z e d in that into the local chamber (1) , when the welding makes progress, more sealing and insu¬ lating material (11) is fed in order to replenish the material that has been consumed.

9. Method as claimed in claim 1, wherein a welding rod (10) or a welding wire is used as the welding member, c h a r a c t e r i z e d in that the rod (10) or wire is fed out of a storage device or equi¬ valent fitted in connection with the local chamber (1 ) , so that the welding rod (10) or wire as well as the local chamber constitute a single unit during the welding and can be shifted at the same time, e.g., by means of one hand.

10. Method as claimed in claim 3, c h r - a c t e r i z e d in that a pasty material that con¬ tains no more than 70, and preferably no more than 40, per cent by weight of additives, such as, e.g., fluorine compounds, is used as the sealing and insulating material (11).