Part for connecting pipes including an internal liner, a covering method, and a method of assembly

Abstract

A method of covering the inside surface of a steel connection part having an empty inside volume ( 1 - 2 ) defined by said inside surface, with a liner constituted by a layer of substantially uniform thickness of a thermoplastic material. The connection part including at least two open tubular ends suitable for being connected respectively to at least two steel pipe elements, each including the same internal liner. A rotary molding method is implemented in which the connection part acts as a mold. The present invention also provides a connection part obtained by the rotary lining method of the invention, and to methods of assembling a connection part of the invention, as obtained by rotary lining, with a likewise lined pipe element.

1 . A steel connection part having an empty inside volume defined by a non cylindrical inside surface, with a liner constituted by a layer of substantially uniform thickness of a thermoplastic material, said connection part having at least two open tubular ends suitable for connecting respectively to at least two steel pipe elements having the same internal liners. 
     
     
         2 . The connection part according to  claim 1 , further comprising at at least one of its ends, a first connecting flange which is welded thereto, said first connecting flange being suitable for co-operating with a second connecting flange of one of said two pipe elements for connection to said connection part. 
     
     
         3 . The connection part according to  claim 1 , wherein at at least one of its said open tubular ends said internal liner of thermoplastic material includes an end portion of thickness that is reduced relative to the thickness of the remainder of said liner, which end portion is obtained by machining and thus defines an inside surface of revolution of inside diameter greater than the inside diameter of the remainder of said internal liner and terminating at a certain distance from the end of said connection part. 
     
     
         4 . The connection part according to  claim 1 , wherein the thermoplastic material comprising of polyethylene, polypropylene, polyamide, and polyvinyl. 
     
     
         5 . The connection part according to  claim 1 , wherein said connection part is a bent pipe element suitable for enabling two pipe elements that extend in different directions to be connected together by being connected to respective ends of said bend element constituting said connection part. 
     
     
         6 . The connection part according to  claim 1 , wherein said connection part is a T-shaped element suitable for enabling three pipe elements to be connected to its respective ends, the elements extending in two directions making between them an angle lying in the range 0 to 90°, and preferably of 90°. 
     
     
         7 . The connection part according to  claim 1 , wherein said connection part is a tapering tubular sleeve presenting two tubular ends of circular cross-sections that are of different inside diameters, suitable for enabling two pipe elements of diameters corresponding respectively to the inside diameters of the two tubular ends of said tapering tubular sleeve to be connected thereto. 
     
     
         8 . The connection part according to  claim 1 , wherein said connection part comprises walls with zones of smaller thickness, said zones of smaller thickness being thermally insulated. 
     
     
         9 . The connection part according to  claim 1 , wherein said layer comprises
 a first layer of a first thermoplastic material; and   a second layer of a second thermoplastic material different from said first material, said second thermoplastic material covering said first material.   
     
     
         10 . The connection part according to  claim 2 , wherein said connection part comprises, at at least one of its tubular ends, said first connecting flange, and the said layer is made continuously over the entire combined inside surface of the connection part and over said first connecting flange with a layer of said thermoplastic material, said first flange being fastened by welding to the end of said connection part. 
     
     
         11 . The connection part according to  claim 10 , wherein said first flange comprises an external bearing face bearing against said second flange and whereby said first flange bears against said second flange, said layer of thermoplastic material being made continuously over said inside surface of the connection part and said inside surface of said first connecting flange, and also over said external bearing face of said first flange bears against said second flange. 
     
     
         12 . An assembly method of assembling a pipe, wherein a connection part is assembled with a pipe element including an internal liner, said connections part comprising:
 an empty inside volume defined by a non cylindrical inside surface, with a liner constituted by a layer of substantially uniform thickness of a thermoplastic material, said connection part having at least two open tubular ends suitable for connecting respectively to at least two steel pipe elements having the same internal liners.   
     
     
         13 . The assembly method according to  claim 12 , wherein:
 said connection part includes a first connecting flange to which it is welded, with the entire combined inside surface of the connection part and of said first connecting flange, and also the external bearing face of said first flange for bearing against said second flange are covered in a said continuous layer of thermoplastic material; and   said pipe element includes at its end a second connecting flange to which it is welded, the entire combined inside surface of said pipe element and of said second connecting flange, and also the external bearing face of said second flange for bearing against said first flange are covered in a said continuous layer of thermoplastic material; and   said first and second connecting flanges are connected together, preferably against an interposed gasket.   
     
     
         14 . The assembly method according to  claim 12 , wherein a said connection part is assembled with a said pipe element with the help of a tubular junction sleeve, and in that said junction sleeve is inserted inside the open tubular end of said connection part at one end of said sleeve, which sleeve presents substantially the same inside diameter as is presented by said internal liner of said connection part. 
     
     
         15 . The assembly method according to  claim 14 , wherein said junction sleeve is inserted:
 via one end of said sleeve into the inside of the open tubular end of said connection part, which end does not have a connecting flange;   via the other end of said sleeve into the inside of the corresponding end of said pipe element, which end does not have a said connecting flange; and   the ends of said connection part and of said pipe element are moved towards each other and welded together over said junction sleeve.   
     
     
         16 . The assembly method according to  claim 15 , wherein the following steps are performed:
 a) said connection part, said pipe element, and said tubular junction sleeve are prepared in such a manner that:   each of the internal liners of thermoplastic material at the open ends of said connection part and of said pipe element includes an end portion of thickness that is reduced relative to the thickness of the remainder of said liner; and   said sleeve presents at each of its ends an end portion of thickness that is reduced relative to the thickness of the central portion of said sleeve, said end portion of the sleeve defining an outside surface of revolution of outside diameter less than the inside diameter of the non-lined ends of said connection part and of said pipe, said sleeve presenting substantially the same inside diameter as said internal liner of the main portions of the connection parts and of said pipe element; and   b) said tubular junction sleeve is inserted into said open tubular ends of reduced thickness of the liner of said connection part and of said pipe element so as to overlap said reduced-thickness end portions of liner.   
     
     
         17 . The assembly method according to  claim 12 , wherein a connection part is assembled and the following steps are performed:
 a) initially the following are prepared:
 said connection part including a first connecting flange to which it is welded, with the entire combined inside surface of the connection part and of said first connecting flange being covered in a said layer of thermoplastic material; 
 said pipe element having at its end a second connecting flange to which it is welded, the entire combined inside surface of said pipe element and of said second connecting flange being covered in a said layer of thermoplastic material; and 
   b) machining the internal liners of thermoplastic material at the ends of said connection part having a said first flange and of said pipe element having a said second flange in such a manner as to create in each of said internal liners an end portion of thickness that is reduced relative to the thickness of the remainder of said liner, and terminating at a certain distance from said ends of said connection part and of said pipe element respectively such that the inside surfaces of said first and second flanges are not lined; and   c) inserting at each of the open ends of said first and second flanges tubular junction half-sleeves for reinforcing the junctions between said connection part and said first flange and between said pipe element and said second flange,   each said half-sleeve presenting:   at its front end, a front end portion of tubular wall of thickness that is reduced relative to the central portion of the tubular wall of said half-sleeves;   at its rear end, a rear end portion of tubular wall of thickness greater than the thickness of the central portion of said half-sleeve;   each half-sleeve being inserted in such a manner that said front end portions of reduced wall thickness of said half-sleeves overlap said end portions of reduced thickness of said liners of said connection part and of said pipe elements respectively;   d) welding said half-sleeves to said first and second flanges respectively at said rear ends of said half-sleeves and external bearing faces of said first and second flanges, respectively; and   e) moving together and fastening to each other said first and second connection flanges.   
     
     
         18 . The assembly method according to  claim 17 , wherein:
 said tubular junction sleeves, and where appropriate said tubular junction half-sleeves are of material that withstands corrosion; and   the outside diameter of the cylindrical central portion of said sleeve or of said half-sleeve is less than the inside diameter of the non-lined ends of the steel walls respectively of said connection part, of said pipe element, or where appropriate of said first and second flanges.   
     
     
         19 . The assembly method according to  claims 17 ,
 wherein the non-lined rear ends of the inside surfaces of said first and second flanges respectively in contact with said rear end portions of said half-sleeves, and said external bearing faces in the zone where said first and second flanges are welded to said rear end portions of said half-sleeves, are locally covered in the same anti-corrosion metal as the metal constituting said half-sleeves.   
     
     
         20 . The assembly method according to  claim 16 , wherein the outside surfaces of said end portions of reduced thickness of said sleeves, or of said half-sleeves, are notched surfaces, having a substantially tapering chamfered end enabling insertion and anchoring against the inside surfaces of the end portions of reduced thickness of the corresponding liners, thus providing a mechanical connection between said outside surfaces of said sleeves or half-sleeves and the inside surfaces of said liners of reduced thickness, merely by forced-engagement of said sleeve, or where appropriate said half-sleeve, in the axial longitudinal direction into said open ends respectively of said connection part, of said pipe element, or of said first and second flanges, respectively.