METHOD FOR BLOCKING PIPES DESCRIPTION OF THE INVENTION The present invention relates to a method and a device for blocking a fluid in a pipe, wherein a hermetically sealed laying unit is mounted and through which a hole is drilled in the pipeline. , with the hermetic seal that is conserved, which allows an expandable body to be inserted through the placement unit, with the help of a locking tool and through the hole drilled in the pipe, to temporarily block the flow of fluid in the pipeline, whereby the expandable body is supported during insertion and in the direction of fluid flow during expansion in the pipe by a support pipe, inserted through the positioning unit circumscribing the locking implement inserted through the pipe. of the placement unit. Prior art methods and devices for temporarily blocking the flow of fluid in a pressurized pipe with a retained hermetic seal are set forth for example in Swedish patents Nos. 8605208-1 and 9301793-7 wherein an expandable body in the form from a rubber balloon introduced into the pipe, it is made to expand and block the pipe. In these cases, the rubber balloon is only held in place by friction against the inner surface of the pipe. This reduces the utility of the device when the fluid has a high pressure and when there are pressure pulsations in the pipe system. It can easily be caused that the rubber balloon slides inside the pipe and finally explodes. Furthermore, the inner surface of welded pipe is not always smooth and may have weld seams, with sharp protuberances easily capable of damaging a sliding balloon, causing the balloon to burst as a result. The object of the present invention is to achieve a method and device according to the patent claims that eliminate these disadvantages, allowing the use of existing blocking methods at very high pipe pressures than those that have been possible to date and exhibit greater crush resistance of expandable block body. This is achieved when a tubular support that circumscribes the locking implement and its expandable body through which the lower part projects to the pipe, is inserted through the positioning unit, the lower part gradually forms an i-cylinder to which the openings face of the fluid flow in the pipe. The lower part of the support tube, which when it is completely inserted into the pipe, approaches the bottom of the pipe, supports the expanded body in such a way that the body does not depend on friction between it and the inner wall of the pipe to maintain in position inside the pipe. This is particularly important in the blocking of heating pipes since hot fluids tend to reduce the friction between the pipe and the rubber balloon, and in the blockage of large diameters where the support tube allows greater expansion of the pipe. rubber balloon. In such a way that a given rubber balloon size and even a certain size for the hole drilled in the pipe, can be used for a plurality of pipe diameters, for example the required number of different sizes can be reduced. Practical tests have shown that the blocking method according to this invention is capable of withstanding fluid pressures that are 3 to 5 times greater than the methods of the prior art using a rubber or expanded rubber balloon. In order to further improve the function of the support tube, especially with large diameter pipes, the lower part of the body can be designed in such a way that it gradually forms a semi-cylindrical rod, with its flat side facing the direction of flow of fluid in the pipeline and equipped with automatically folded fins, which are movably mounted on the flat side of the rod and are attached to the side, when the body touches the bottom of the pipe. Correspondingly, the fins retract towards the center of the rod, when they touch the inner surface of the upper part of the pipe, as the locking implement is removed from the pipe, in order to allow the passage of the body through the pipe. Hole drilled in the pipe. BRIEF DESCRIPTION OF THE DRAWINGS The method and one embodiment of the method will be described in the patent claims and appended figures, wherein Figure 1 shows a side view of the invention, with the support tube mounted inside the positioning unit and with the locking device in its upper position, before the expandable body is inserted in the pipe to be blocked. Figure 2 shows the same side view, but after the expandable body has been inserted into the pipe. Figure 3 also shows a side view where the expandable body has expanded to block the pipe. Figure 4 is a schematic cross-sectional view of the support tube and the fins, before the tube is inserted into the pipe. Figure 5 shows the support tube with the flaps folded down after the tube has been inserted into the pipe. In Figure 1, 1 is the part of the pipe in which the flow is to be blocked, 2 is a laying unit, which with the aid of a threaded connector (not shown) is connected to the pipe, in such a way that an airtight sealer is achieved. The positioning unit is equipped with a valve device 5, operated by a bore or support tube 9, and has a screwed extension part 12, which at its uppermost end has an internal sealing body 4 designed to seal against a bore or the support tube 9. The extension part is equipped with a rotatably arranged steel bracket 15, which clamps a locking device 14 to the extension part. The locking device 14 comprises a locking cylinder 16 loaded with spring 19, of which the locking pin fixes the locking implement 7, when coupling the notch of the implement 17, when the support tube 9 is inside the positioning unit 2 and the extension part 12 and when engaging the notch 18 after the block implement with the expandable body 8, has been inserted into the pipe 1. The tubular support 9 consists of a thin-walled tube that is vertically slidable within of the extension part of the positioning unit and which is hermetically sealed by the seal body 4. Its upper section has a collar 13 which fixes the position of the tube in relation to the extension part. The part of the support tube projecting into the pipe 1, gradually forms a semi-cylinder 10 of which the opening 11 faces the direction of fluid flow in the pipe and is intended to serve as a support for the expandable body, especially in the expanded state, during blockage and fluid flow in the pipeline. The locking increase 7 with the expandable body 8 is inserted into the support tube 9 with the locking device 14 of which the locking pin is made to engage the notch in the locking implement 17 within the positioning unit 2. and the extension 12 and is fixed thereto by the locking clamp 15. In this position, the lower part 10 of the support tube is in its final position inside the pipe 1, while the expandable body 8 is inside the cavity. of the positioning unit 6. Figure 2 shows the position of the locking implement after the locking cylinder 16 has been detached from the notch 17, and the implement with its expandable body has been pushed down into the pipe and slanted in position, when the locking cylinder is made to engage the notch 18. The upper end of the block attachment has a multiple connection lug 24 with a plugged-in connector., a connection for compressed air 26 and a connection or a pressure gauge 27. In Figure 3, the compressed air has been supplied through the connection 26, to expand the expandable body until sufficient pressure has been achieved as illustrated in the pressure gauge 27. This blocks the pipe. The locking implement is removed in the corresponding way after blocking. The compressed air is evacuated through the connection 26, the implement 27 is removed until the locking cylinder engages the notch 17 and the support tube with the locking implement, is detached from the locking clamp and removed from the unit of placement. The valve device 5, then automatically closes to prevent leakage of fluid from the pipe 1. Figure 4 shows a schematic cross-section of the support pipe 4, equipped with automatically lowered and retracted fins 20a and 20b, before insertion into the pipe 1. The fins, which overlap each other here, are slidably connected to the side of the rod fin of the support tube by two pins equipped with head 22, which slide in the slots 21, which run at an angle of 45 ° with respect to the horizontal plane in the fins. Finally, Figure 5 shows the device with the support tube fully inserted in the pipe 1. Here, the fins have increased the support area. Since the fins 20a and 20b in the lowered position extend further down than the support tube rod, they are forced away by the oblique grooves, as they pass down the pipe, thereby increasing the support area. Correspondingly, the fins are forced together when the support tube is removed from the pipe. The invention is not limited to the illustrated embodiment, but may even comprise other solutions that incorporate an extension of the supporting section of the support tube for example by opening wings or hinged fins.