There exist a method and an appliance for inner anti-corrosion protection of welded joints of the pipes with full-length (except the ends) inner anti-corrosion coating (RF Patent No. 2080510, Cl. F16L13/02, Application No. 95108103/06 as of 18 May 1995, published 27 May 1997. Authors: V. A. Kazakov, S. V. Kolesnev, E. P. Syntin, N. I. Kanashouk). The appliance contains a rigid metal socket with gaskets in its outer ends'grooves. In the socket's central part, on its outer surface, there exists a channel housing some heat-insulation material.

Before installation of the appliance into the pipes to be welded, sealing compound is applied to the inner surface of the ends of these pipes. The appliance is inserted into the coupled pipe ends, when the joint is being assembled for welding. For quality anti-corrosion protection with this appliance and this method, it is necessary, on the one hand, for the appliance's outer diameter not to outsize the inner diameter of the coupled pipes. On the other hand, it is necessary not to allow extremely large gaps. However, the normatively allowed deviations of standard pipes'form and size are such that the observance of the above-stated conditions is not guaranteed. Besides, if we take into consideration the possible substantial random geometry deviations of pipe ends'form and size, caused by loading, transportation, discharge, storage, etc. , it appears that this method is unlikely to be used successfully.

It is desirable to have a method and an appliance that would allow to compensate deviations in geometry size and form of the inner surfaces of the coupled pipes.

There exist a method and an appliance for inner anti-corrosion protection of welded joints of the pipes with full-length (except the ends) inner anti-corrosion coating, developed by Tuboscope Vetco International (USA) and demonstrated at 10th International Oil and Gas Exhibition in Moscow, in July 2001 (see Tuboscope Vetco International advertising booklets). The appliance contains a rigid metal socket with gaskets in its outer ends'grooves. In the socket's central part, on its outer surface, there exists a channel housing some heat-insulation material in the form of ring belt. Before installation of the appliance into the pipes to be welded, sealing compound is applied to the inner surface of the ends of these pipes. The appliance is inserted into the coupled pipe ends, when the joint is being assembled for welding. The size and form of the socket ends'outer surfaces, and of pipe ends'inner surfaces should allow for the required space at coupling. For this, taking into consideration the possible deviations in size and form of the pipes, their inner surface is calibrated. The calibration should be accurate enough to provide for elements'interchangeability.

This method and construction, by their aggregate characteristics, are the closest to those required, and they serve as prototype both for the method and the appliance.

The necessity for calibration of the inner surface of the pipes complicates the application of the method and the appliance, and increases spending.

It is desirable to have a method and an appliance for inner anti-corrosion protection of welded joints of the pipes that would allow to compensate deviations in geometry size and form of the inner surfaces of the coupled pipes, and to exclude calibration, which would simplify the method and cut the expenses.

The task may be solved in the following way. The method for inner anti- corrosion protection of welded joints of the pipes, when an appliance containing a socket and heat-insulation material in the form of ring belt in its central part, is inserted into the joint area and the neighboring protection coating of the pipes, has been subjected to innovations. The socket is manufactured in the form of spiral ribbon equipped by sealant. The spiral ribbon represents a self- unwrapping spring accumulating estimated amounts of mechanic energy, temporarily embraced by knuckle-joint compact assembling knot, fixing the spring and protecting it from self-unwrapping, which knot may be then undone and removed. The ring belt heat-insulation material is stretchable. Before welding of the pipes, on the end of one of the pipes a knuckle-joint compact assembling knot is placed, fixing the spring and protecting it from self- unwrapping. The socket is partially inserted and centered inside one of the pipes to be coupled, and the pipes are assembled for welding, by way of sliding the other pipe's end over the protruding part of the appliance. Between the ends of the pipes, a gap is established, whose minimal amount is determined by the knuckle-joint compact assembling knot. The spiral ribbon with sealant is pressed, with estimated force, to the inner surface of pipe joint, by way of undoing the knuckle-joint compact assembling knot and its subsequent removal from the pipe joint, which leads to unfixing and partial self-unwrapping of the ribbon by its accumulated mechanical energy. Then the pipes are welded together.

The task is solvable in the following way. The appliance for inner anti-corrosion protection of welded joints of the pipes, containing a socket and heat-insulation material in the form of ring belt in its central part, has been subjected to innovations. The socket is manufactured in the form of spiral ribbon equipped by sealant. The spiral ribbon represents a self-unwrapping spring accumulating estimated amounts of mechanic energy, temporarily embraced by knuckle-joint compact assembling knot, fixing the spring and protecting it from self- unwrapping, which knot may be then undone and removed. The ring belt heat- insulation material is stretchable. The spiral ribbon may be made corrosion- resisting. Glass-fiber fabric with appropriate interweaving may be taken as the stretchable heat-insulation material. The knuckle-joint compact assembling knot may have the form of tongs.

The invention is illustrated graphically. Fig. 1 shows the appliance partially inserted into one of the pipes to be coupled; Fig. 2 shows A-A section for Fig. 1 ; Fig. 3 shows the position of the appliance inside the tubes at the moment of removing the knuckle-joint compact assembling knot; Fig. 4 shows the knuckle- joint compact assembling knot after its being undone in the joint area; Fig. 5 shows the joint after the knuckle-joint compact assembling knot has been undone and removed, and the ribbon equipped with sealant is pressed to the inner surface of the joint.

The appliance contains a socket manufactured in the form of spiral ribbon 1 equipped by sealant 4, and representing a self-unwrapping spring accumulating estimated amounts of mechanic energy, temporarily embraced by knuckle-joint compact assembling knot 2, fixing the spring and protecting it from self- unwrapping, which knot may be then undone and removed, and heat-insulation 3. The width and thickness of heat-insulation 3 protects the spiral ribbon 1 equipped by sealant 4, from heat attack when the pipe joint is being welded. The knuckle-joint compact assembling knot 2 includes lever bracket 11, lever bracket 12, joint 13 and lock 14. Between the ends of the pipes 5 and 6, there exists gap 9. Sealant 3, partially squeezed out at the moment of partial unwrapping of spiral ribbon 1, forms protection bumpers 10.

The method is implemented as follows. The knuckle-joint compact assembling knot 2, fixing the socket, is placed on the end of one of the coupled pipes 5, with inner surface 7. Basing on the outer surface of the end of pipe 5, the knuckle- joint compact assembling knot 2 centers the socket, which is partially inserted into the coupled end of pipe 5. The cross-sectional size of the socket equipped by sealant 4 and heat-insulation 3, is substantially smaller than the inner diameter of pipes 5 and 6, which allows to avoid penetration of sealant 4 both to the rim of pipe 6 and its neighboring inner surfaces (during sliding tube 6 over the appliance). The joint of pipes 5 and 6 is assembled, by way of sliding tube 6 over the protruding end of the appliance, making gap 9, whose width is regulated by lever brackets 11 and 12 of the knuckle-joint compact assembling knot 2. The knuckle-joint compact assembling knot 2 is undone using lock 14; the lever brackets 11 and 12 get angle movement around joint 13; the knuckle- joint compact assembling knot 2 is removed from between pipes 5 and 6. When the knuckle-joint compact assembling knot 2 is undone, ribbon 1 is partially unfixed and self-unwrapped by way of part of the mechanical energy it accumulates. The ring belt made of heat insulation 3 is stretched; the inner surfaces of the coupled pipes 5 and 6 limit the self-unwrapping of ribbon 1. The remaining part of the mechanical energy accumulated in ribbon 1 equipped with sealant 4, provides for the ribbon's pressing to the tubes'inner surface with estimated force. When necessary, gap 9 is regulated by axial shift of one of the coupled pipes. Ends of the tubes 5 and 6 are welded according to traditional technology, with or without preliminary tack weld. Heat insulator 3 possesses the required thermal resistance and heat resistance, and excludes the unacceptable heat influence upon the thermosensitive sealant 4. The estimated force pressing ribbon 1 provides for the required amount of sealing in the welding joint area of the pipeline, protecting it from the substances it carries inside; it also prevents excessive squeezing of sealant 4. The required amount of mechanical energy left in ribbon 1 after its pressing, depends of the pipeline's diameter, physical and mechanical properties of the sealant and the heat- insulation, as well as of other characteristics required for the calculation of properties and parameters of ribbon 1, its cross-section axial moment of inertia, its working length, etc. Sealant 4, partially squeezed out at the moment of partial unwrapping of spiral ribbon 1, forms protection bumpers 10 along the whole ribbon 1, which additionally increases reliability of the inner anti-corrosion protection of the welded joint area. Thus, manufacturing the socket in the form of spiral wrapped ribbon equipped with sealant and representing a self- unwrapping spring, taking into consideration the fact that its self-unwrapping is limited by actual surface of the ends of the coupled pipes with definite size and form deviations, each time allows to compensate for the actual deviations, and to each time get the required connection in the"socket-pipe end"system.

Polymerization of sealant 4 may be conducted by outer heating of the tubes from outside source, but it also may require no specialized heating, taking into consideration the sealant's properties. Besides, a certain amount of heat required for sealant polymerization, may be accumulated in the appliance's body beforehand.

Example of actual making of the appliance. Metal ribbon wrapped as spiral is made of spring cold-rolled cold-hardened steel tape, GOST 2283-79, 0.5 mm thick. The heat-insulation represents high-temperature resistant stretchable glass-fiber fabric 3 mm thick, formed as ring belt. Thixotropic (non-dripping) epoxy compound is taken as sealant. The metal ribbon is treated with corrosion- proof hardened coating based on epoxy resin 0.5 mm thick. The knuckle-joint compact assembling knot has the form of tongs. The pipeline whose welded joint is being protected, is manufactured from steel electric arc welding pipes GOST 20295-85, with inner full-length anti-corrosion coating based on epoxy resin, except the ends. Inner diameter of the pipeline: 219 mm; walls are 7 mm thick. Outer cross-sectional diameter of the appliance: about 180 mm, length: 240 mm.