Apparatus and method for coating pipes or pipe sections
The invention relates to an apparatus and method for coating a pipe or a section of a pipe with a polymer layer. The apparatus comprises an applicator for applying polymer melt on the surface of a pipe or pipe section, a roller for pressing the polymer applied by the applicator towards the pipe or pipe section, and means for circumferentially moving the applicator and the roller around the periphery of the pipe or pipe section. According to the invention the apparatus further comprises a drive for rotating the roller as the roller is moving around the periphery of a pipe or pipe section. By means of the invention, higher quality coatings can be applied to field joints of steel pipes, for example.
1. An apparatus for coating a pipe or a section of a pipe with a polymer layer, comprising:
an applicator for applying polymer melt on the surface of a pipe or a pipe section;
a roller for pressing the polymer applied by the applicator towards the pipe or the pipe section, the roller having a central axis;
means for circumferentially moving the applicator and the roller around a periphery of the pipe or the pipe section at a circumferential speed,; and
a drive for rotating the roller actively around a central axis of the roller as the roller moves around the periphery of a pipe or the pipe section,
wherein the drive for rotating the roller is configured to actively rotate the roller at a rotating speed that is essentially equal to the circumferential speed.
2. The apparatus according to claim 1 , wherein the means for circumferentially moving the applicator and the roller comprises a carriage, the roller and the drive of the roller being mounted on the carriage.
3. The apparatus according to claim 1 , wherein the drive is an electric motor.
4. The apparatus according to claim 1 , wherein the surface of the roller comprises at least one elastic material.
5. The apparatus according to claim 1 , wherein the surface of the roller comprises at least a hard materiale.
6. The apparatus according to claim 1 , wherein the roller is profiled along its central axis.
7. The apparatus according to claim 1 , wherein the applicator is arranged to form a film made of polymer melt and to feed the film to a nip formed by the roller and the surface of the pipe section or the pipe.
8. The apparatus according to claim 1 , wherein the applicator and means for circumferentially moving the applicator are adjustable to rotate the roller at a speed to provide a negative draw-down of the polymer.
9. The apparatus according to claim 1 , wherein the movable carriage comprises a support means to fasten the carriage to the pipe, allowing the carriage to automatically run move around the periphery of the pipe or the pipe section.
10. The apparatus according to claim 9 , wherein the support means comprises at least one chain releasably attached to the pipe or the pipe section.
11. The apparatus according to claim 1 , wherein the drive is further configured to variably drive the rotating speed of the roller.
12. A method of coating a pipe or a section of a pipe with a polymer layer, the method comprising:
providing a pipe or a pipe section having an outer surface defining the periphery of the pipe or the pipe section;
applying on the outer surface of the pipe or the pipe section a layer of at least one polymer material in a melted state with an applicator, the applicator being mounted on a carriage capable of travelling along a periphery of the pipe or the pipe section;
moving the carriage along at least a part of the periphery of the pipe or the pipe section at a circumferential speed;
pressing the applied polymer material towards the pipe or the pipe section with a roller having a central axis while moving the carriage; and
rotating the roller around its own the central axis of the roller during the pressing,
wherein step of rotating the roller actively rotates the roller at a rotating speed that is essentially equal to the circumferential speed.
13. The method according to claim 12 , wherein the coating is applied on a girth weld between two steel pipes.
14. The method according to claim 12 , wherein said polymer is a polyolefin.
15. The method according to claim 12 , wherein the rotation of the roller is achieved using a drive which is mounted on the movable carriage.
16. The method according to claim 12 , wherein the polymer layer is given a desired surface profile in the axial direction of the pipe or the pipe section by using a roller which is profiled along the central axis of the roller to match the surface profile of the pipe or the pipe section.
17. The method according to claim 12 , comprising feeding a polymer film from the applicator between the roller and the surface of the pipe or the pipe section.
18. The method according to claim 12 , wherein the carriage speed is controlled to allow the polymer material from the applicator to be applied by at negative draw-down.
19. The method according to claim 12 , wherein the carriage is fastened to the pipe or the pipe section using a support means during moving of the carriage and application and pressing of the polymer.
20. The method according to claim 12 , wherein said polymer is polyethylene or polypropylene or a modified polyolefin.
21. An apparatus for coating a pipe or a section of a pipe with a polymer layer, comprising:
an applicator configured to apply polymer melt on the surface of a pipe or a pipe section;
a roller configured to press the polymer applied by the applicator towards the pipe or the pipe section, the roller having a central axis;
a carriage configured to circumferentially move the applicator and the roller around a periphery of the pipe or the pipe section at a circumferential speed; and
a drive configured to rotate the roller actively around a central axis of the roller as the roller moves around the periphery of a pipe or the pipe section,
wherein the drive is set to actively rotate the roller at a rotating speed substantially equal to the circumferential speed.