The present invention relates to a grinding tool for flanges in a pipe coupling comprising, at least, one first stationary part fastened to the flange, and also a second rotary part equipped with a grinding tool for grinding the free surface of the flange.

There is a requirement on off-shore installations today that all work shall be EX- certified and in connection with high temperature work it is therefore common for a habitat to be set up, i.e. a tent type construction that is kept at an overpressure, around the work place where the high temperature work shall be carried out. In addition, warning and shut down installations with gas detection and fire warning are often incorporated. To grind flanges in pipe couplings it has therefore been common, up until now, to set up such habitats for high temperature work in connection with the cutting of the flanges that are to be ground. Thereafter, the flanges are brought ashore for further processing before they are brought back to the offshore installation and mounted. If the habitat is removed in the meantime, it must be erected again. Therefore is not uncommon for it to take up to 14 days to complete the job of grinding flanges.

With the present invention one aims to reduce the required processing time considerably, possibly to as little as about 2 hours for the grinding of both the flanges in a pipe coupling.

This is achieved in that a tool has been developed which uses components that certifies it for use in EX zones 1 & 2 and dust, as it uses low temperature equipment. The tool can be used in EX zones both offshore and onshore. In the present tool a rotating file can be used for low temperature filing, and which can be manufactured in a circular-cylindrical shape of, for example, more than 95% tungsten carbide, and also a special alloy that provides extra wear strength and thus extends the life time of the tool. The teeth of the file are cut out in a special process and this ensures that when the file makes contact with the base it grinds in such a way that the tool neither slides nor rubs against the base and therefore does not generate unnecessary heat. By the expression "low temperature" is meant in the main temperatures below 70 °C and preferred in this context are below 60 °C. In relation to the special rotating file, the speed of rotation can also be held low, for example, between 800 and 3000 rpm, which also results in less heat generation. In the present embodiment examples the speed can lie at about 2000 rpm, which is low in this context.

From prior art reference is made among others to US 2004/0187657, which relates to a tool for the grinding of flanges externally. The tool comprises a first part which is fastened to the flange and a second part that rotates relative to the first part with the help of an air motor and belt drive. Fastened to the rotating part is a cutting tool that can be regulated in the form of a rotating blade that can be moved in and out from the centre of the flange. The tool further comprises a number of clamps to regulate the position of the tool in relation to the flange.

One disadvantage with the tool described in US 2004/0187657 is that much heat is generated and it can therefore not be used in an EX environment on offshore installations. Another disadvantage is that the tool is assembled in such a way that it takes up a relatively large amount of space. Therefore, it is not suited to be placed between two flanges in a pipe coupling, which is contrary to the present invention which can be placed between two flanges spaced only 60-80 mm apart.

The above mentioned object is achieved with a tool that is given in the independent claim 1 , in that the grinding tool is shaped as a rotating file and that the rotating file lies level with the free surface of the flange and is placed in a holding and adjusting arm that extends diagonally across the flange.

Alternative embodiments are given in the dependent claims.

The first stationary part can comprise two half-moon shaped plate parts arranged to envelop the pipe and for fastening to the rear side of the flange, with the help of bolts that run through the normal bolt holes of the flange, and also a ring-shaped fastening plate that lies externally around the circumference of the flange and which is fastened to said plate parts.

The rotating part can further comprise a ring-shaped holding plate arranged externally to the ring-shaped fastening plate, in which the holding and adjusting arm is located in diagonally opposite recesses in the ring-shaped holding plate. The ring-shaped holding plate can be adjusted and be held against the ring- shaped fastening plate with the help of a number of fastening and adjusting pieces.

The holding and adjusting arm is preferably adjusted and fastened to the ring- shaped holding plate with the help of a number of fastening and adjusting screws. The holding and adjusting arm can be equipped with an opening in which the rotating file is placed, and the rotating file can be connected to a drive shaft for the rotation of the file.

The drive shaft can be connected to a motor drive. Furthermore, the ring- shaped holding plate can be connected to a motor drive arranged to rotate the plate.

The rotating file is preferably made in a cylindrical-circular shape and manufactured from more than 95% tungsten carbide.

The tool can be equipped with one or more spirit levels for the adjustment of the position of the tool in relation to the flange. Furthermore, the tool can be equipped with one or more measuring means for the reading and adjusting of the position of the rotating file in relation to the flange.

The invention shall now be described in more detail with the help of the enclosed figures, in which;

Figures 1 and 2 show perspective views of the tool according to the invention seen from the front and back, respectively.

Figures 3 and 4 show partially exploded perspective views of the tool according to the invention, seen from the front and the back, respectively.

Figure 5 shows a holding and adjusting arm for a rotating file according to the invention.

As mentioned, it is time consuming to grind the flanges of a pipe coupling. The present invention provides a swift and alternative method for on-site grinding of the flanges without the flanges having to be removed. Furthermore, activities in other adjoining pipelines can be maintained while the grinding takes place, in contrast to other known solutions. Before the tool according to the invention is mounted, the pipe coupling must be dismantled and the two flanges that lie against each other must be pulled some apart, but usually not more than the 60-80 mm, as mentioned above. The grinding tool comprises a first stationary part 14 which is fastened to the rear side of the flange, i.e. the side opposite to the packer surface and the bolt surface. The part 14 comprises two halves 14a, 14b with, for example, a "half- moon" shape, which surround the pipe 10 when assembled. The two halves 14a, 14b are preferably fastened to fastening bolts (not shown) which are led through the normal bolt holes of the flange 12. The heads of the fastening bolts can be shaped so that they lie inside the bolt surface, and the fastening bolts can be placed in linings or cases.

After the fastening bolts are put in place, each of the two halves 14a, 14b are fastened to the flange 12. Spacers (not shown) can be used between the two halves to regulate the distance between the halves according to the diameter of the flange. Thereafter, a ring-shaped fastening plate 24 is fastened to the flange 12 and to the stationary part 14, preferably with the help of bolts 32. A ring-shaped holding plate 16 is arranged externally to the ring-shaped fastening plate 24, where the ring-shaped holding plate 16 is arranged to rotate about the fastening plate 24. The holding plate 16 preferably lies externally against the circumference of the fastening plate 24, and is held in position and adjusted with the help of several holding and adjusting pieces 22. A holding and adjusting arm 18 is arranged diagonally in the ring-shaped holding plate 16 in separate recesses 28a, 28b, so that it extends across the centre of the flange 12. Thereby, the holding plate 16 is held in position about the fastening plate 24 with the help of the holding and adjusting pieces 22 lying behind and the arm 18 lying at the front.

For grinding of the packer surface and the bolt surface of the flange, a rotating file 20 is placed in the holding and adjusting arm 18, where the rotating file 20 can be shaped in a cylindrical-circular shape and, for example, manufactured from more than 95% tungsten carbide and a special alloy that provides extra resistance to wear. The rotating file 20 rests in a suitable bearing arrangement in an opening 32 in the arm 18 and can be fastened and held in place with the help of fastening pieces 34a, 34b. Furthermore, the rotating file 20 can be connected to a drive shaft 26 that extends through the arm 18. For rotation of the file the drive shaft 26 is connected to a motor drive (not shown) which can be connected in a conventional way. The motor drive can, for example, be an air motor or other known type of motor. The free surfaces of the flange 12 are ground in that the file 20 rotates at the same time as the outer ring-shaped plate 16 rotates. The rotation of the outer plate 6 can be made manually or with the help of a motor drive (not shown) which can be connected in a conventional way. After the rotating file is set up, the packer flange is preferably ground first, and thereafter the file is adjusted and the bolt surface is ground.

For adjustment of the position of the tool in respect to the flange, the tool can be equipped with one or more spirit levels placed on, for example, the outer ring-shaped holding plate 16. Furthermore, the tool can be equipped with one or more measuring devices for the reading and adjusting of position of the rotating file 20 with respect to the flange, for example, placed between the arm 18 and the flange 12.