Method for protecting a welded joint between pipes having an interior coating

Abstract

In the proposed method, a protective sleeve is plastically deformed to dimensions enabling the shape of the sleeve to correspond to the shape of the interior surface of the pipes to be joined in the joint region. The deformed sleeve is installed inside the pipes to be joined such that an annular cavity is formed between the sleeve and the region of the welded joint together with the adjacent portions of the pipes protected by a coating. The ends of the pipes are joined by welding and the annular cavity is hermetically sealed at the ends of the sleeve. Once sealed, the cavity is evacuated and, via working apertures in one or both of the pipes to be joined, the annular cavity is filled with a liquid sealing material, which is then polymerized. During installation of the protective sleeve, a steel cushioning ring can additionally be positioned between the sleeve and the welded joint, wherein the outside surface of the cushioning ring contacts with the surface of the welded joint and the inside surface of the cushioning ring is provided with projections which contact with the outside surface of the sleeve. As the joint is welded, the ends of the pipes are welded to the steel cushioning ring. The technical result is more reliable and durable corrosion protection of a welded pipe joint.

1 - 8 . (canceled) 
     
     
         9 . Method for inside anti-corrosion protection of welded joints of pipes with an interior protective coating, which comprises: placement of a protective liner coaxially inside the pipes to be joined, with formation of an annular cavity between the outer surface of the liner and the inside surface (to be insulated) of the weld joint of the pipes with adjacent coating-protected areas; welding of the pipe ends; sealing-off of the annular cavity at liner edges; filling of the annular cavity with a liquid sealant agent via at least one process hole in one or both pipes with subsequent polymerization of the agent, wherein prior to the placement of the protective liner, it is plastically deformed by means of stretching the liner parts to ensure matching the shape and internal diameter of each part of the liner to the shape and internal diameter of the opening of respective pipe in the area of the joint, taking into account the mounting gap between them and the thickness of the inside protective coating, and the placement of the protective liner is effected in the form of inserting one part of the liner into one pipe until it gets rested against the sealant applied onto its inside surface, and then pushing the second pipe onto the other part of the protective liner until it gets rested against the sealant on the inside surface of the second pipe. 
     
     
         10 . Method according to  claim 9 , wherein the annular cavity is filled with a liquid sealing material by means of evacuating the annular cavity followed by feeding said material therein, and then exposing said material to the effect of atmospheric or excess pressure. 
     
     
         11 . Method according to  claim 9 , wherein when placing the protective liner, in between the protective liner and the weld joint a steel annular cushion is arranged, which contacts with its outer surface to the weld joint surface and has projections on its inside surface that are in contact with the outer surface of the protective liner, and when welding pipe ends, they are welded to the steel annular cushion. 
     
     
         12 . Method according to  claim 9 , wherein the protective liner has annular projections on the outer surface of its end parts. 
     
     
         13 . Method according to  claim 9 , wherein in the course of the plastic deformation of the liner annular projections on the outer surface of its end parts are formed. 
     
     
         14 . Method according to  claim 12 , wherein, prior to the placement of the protective liner, a reinforcing, well impregnable material resistant to aggressive environments is applied onto the liner's outer surface in between the annular projections. 
     
     
         15 . Method according to  claim 9 , wherein the airtightness of weld joint insulation is checked both prior to and after the filling of the annular cavity with the liquid sealant material by means of evacuation and subsequent assessment of the rate of air/gas leakage into the annular cavity. 
     
     
         16 . Method according to  claim 9 , wherein the protective liner is made of stainless steel and has a wall thickness ranging from 0.1 to 6.0 mm.