Isolation barrier assembly

1. A method of manufacturing an assembly for use as an isolation barrier, which when assembled comprises:

a first tubular section, the first tubular section including: at a first end a coupling to connect the first tubular section to a tubular string; a mandrel portion extending to a second end; and an annular face formed on a ledge arranged circumferentially around and extending radially outwards from an outer surface of the first tubular section;

a second tubular section, the second tubular section including: at a first end a coupling to connect the second tubular section to a tubular string; and at a second end, an annular face arranged perpendicularly to a central axis of the second tubular section;

a sleeve body, being a tubular section having first and second end faces, respectively, at each end thereof;

wherein: the sleeve body is arranged over the mandrel portion between the first and second tubular sections; the annular face of the first tubular section is welded to the first end face of the sleeve body; the annular face of the second tubular portion is welded to the second end face of the tubular body; and the mandrel portion is connected to the second tubular portion so as to create a chamber between the sleeve body and the mandrel portion, which can be filled with fluid via a port in the mandrel portion so as to expand the sleeve body;

the method comprising the steps, in order:

(a) welding the annular face of the second tubular section to the second end face of the sleeve body;

(b) machining at least the inside of the sleeve body and the inside of the second tubular portion to provide a central bore of a first diameter, through the sleeve body and the second tubular portion at the weld;

(c) sliding the sleeve body over the mandrel portion;

(d) coupling the mandrel portion to the second tubular section; and

(e) welding the annular face of the first tubular section to the first end face of the sleeve body.

2. A method according to claim 1 wherein the annular face arranged perpendicularly to the central axis of the second tubular section is provided on a ledge so that the sleeve body is supported at the second end face for the welding at step (a) to be carried out.

3. A method according to claim 2 wherein at step (b) machining removes a portion of the second tubular section so that only the ledge remains and the welded joint provides connection of two abutting annular faces.

4. A method according to claim 1 wherein the weld at step (a) is formed by a different technique than the weld at step (e).

5. A method according to claim 1 wherein the weld at step (a) is a gas metal arc weld (GMAW).

6. A method according to claim 1 wherein the weld at step (e) is an electron beam weld (EBW).

7. A method according to claim 1 wherein the weld at step (a) is an electron beam weld (EBW).

8. A method according to claim 1 wherein the weld at step (e) is a gas metal arc weld (GMAW).

9. A method according to claim 1 wherein the coupling between the mandrel portion and the second tubular section is by screw-threads.

10. A method according to claim 1 wherein the method includes a further step of machining over the weld of step (e).

11. A method according to claim 1 wherein the method includes the step of selecting a sleeve body having a material which yields more easily under pressure than the material of the first and second tubular sections.

12. A method according to claim 1 wherein the method includes the step of machining the outer surface of the sleeve body over a portion thereof, to reduce a thickness of the sleeve body.

13. A method of manufacturing an assembly for use as an isolation barrier, which when assembled comprises:

a first tubular section, the first tubular section including: at a first end a coupling to connect the first tubular section to a tubular string; a mandrel portion extending to a second end; and an annular face formed on a ledge arranged circumferentially around and extending radially outwards from an outer surface of the first tubular section;

a second tubular section, the second tubular section including: at a first end a coupling to connect the second tubular section to a tubular string; and at a second end, an annular face arranged perpendicularly to a central axis of the second tubular section;

a sleeve body, being a tubular section having first and second end faces, respectively, at each end thereof;

wherein: the sleeve body is arranged over the mandrel portion between the first and second tubular sections; the annular face of the first tubular section is welded to the first end face of the sleeve body; the annular face of the second tubular portion is welded to the second end face of the tubular body; and the mandrel portion is connected to the second tubular portion so as to create a chamber between the sleeve body and the mandrel portion, which can be filled with fluid via a port in the mandrel portion so as to expand the sleeve body;

the method comprising the steps, in order:

(a) welding the annular face of the second tubular section to the second end face of the sleeve body, wherein the annular face arranged perpendicularly to the central axis of the second tubular section is provided on a ledge so that the sleeve body is supported at the second end face for the welding to be carried out;

(b) machining the sleeve body and the second tubular portion to provide a central bore of a first diameter over the weld and the machining removes a portion of the second tubular section so that only the ledge remains and the welded joint provides connection of two abutting annular faces;

(c) sliding the sleeve body over the mandrel portion;

(d) coupling the mandrel portion to the second tubular section; and

(e) welding the annular face of the first tubular section to the first end face of the sleeve body.