System for improving flexibility of riser supports in stationary production units and installation method

Abstract

The present invention addresses to a system consisting of one or more pipes of low flexural rigidity (upper and intermediate extension pipes), connected to a thicker pipe section (lower extension pipe) by means of a varied cross-section pipe (conical profile) and further an adapter shaped like a helmet of a bend stiffener of a flexible riser, to enable, without operational losses, the use of rigid risers in Stationary Production Units (SPUs) initially designed to receive only flexible risers, therefore not having specific supports for rigid risers. The low flexural rigidity of the pipe is achieved through the correct selection of specific materials, preferably by using a titanium alloy that has a low modulus of elasticity and a high yield strength compared to steel.

1 . A system for flexibilization of riser support in stationary units, comprising an upper I-tube ( 15 ), a lower I-tube ( 13 ), a bell mouth ( 7 ), an adapter helmet ( 5 ), and characterized in that it comprises an upper extension pipe ( 1 ), an intermediate extension pipe ( 2 ), a lower extension pipe ( 3 ) and a varied cross-section pipe ( 4 ). 
     
     
         2 . The system according to  claim 1 , characterized in that the upper extension pipe ( 1 ) is positioned at the upper end of the system and has a lower flange that connects to the section of intermediate extension pipe ( 2 ). 
     
     
         3 . The system according to  claim 2 , characterized in that the number and length of sections of the intermediate extension pipe ( 2 ) depend on the distance between the upper I-tube ( 15 ) and the lower I-tube ( 13 ). 
     
     
         4 . The system according to  claim 1 , characterized in that the lower end of the intermediate extension pipe ( 2 ) connects to the section of lower extension pipe ( 3 ). 
     
     
         5 . The system according to  claim 1 , characterized in that the section of the lower extension pipe ( 3 ) promotes a curvature (flexion) inside the adapter helmet ( 5 ). 
     
     
         6 . The system according to  claim 1 , characterized in that the extension pipes ( 1 ), ( 2 ) and ( 3 ) are connected to each other by means of compact type flanges ( 6 ), or circumferential welds. 
     
     
         7 . The system according to  claim 1 , characterized in that the lower end of the lower extension pipe ( 3 ) is connected to a stress joint or flexible joint ( 10 ), replacing the varied cross-section pipe ( 4 ). 
     
     
         8 . An installation method of the system for flexibilization of risers according to the inventive concept presented in  claim 1 , characterized in that there are the following steps:
 Fixing the adapter ( 5 ) to the top tube ( 1 ) by means of a collar containing fusible cables ( 8 );   Starting the pull in procedure of the set of extension pipes ( 1 ,  2  and  3 ) by the platform winch cable passing inside the lower I-tube ( 13 ) and through the bell mouth ( 7 );   Locking the adapter helmet ( 5 ) whose weight will be supported by Dogs ( 14 );   Continuing to slide the set of extension pipes ( 1 ,  2  and  3 ) inside the adapter helmet ( 5 ) and bell mouth (or multifunctional bell mouth) ( 7 ) until its top end reaches the upper I-tube ( 15 );   Assembling a support ( 9 ) around the flange of the upper extension pipe ( 1 ), connecting it to the vessel piping through a top flange ( 11 ).   
     
     
         9 . The system according to  claim 3 , characterized in that the lower end of the intermediate extension pipe ( 2 ) connects to the section of lower extension pipe ( 3 ). 
     
     
         10 . The system according to  claim 4 , characterized in that the section of the lower extension pipe ( 3 ) promotes a curvature (flexion) inside the adapter helmet ( 5 ).