Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
74 words
A method for production of multi-layer gap-less steel pipes comprising matching individual helical welding seam steel pipes of about the same length with a difference of less than about one percent between the outer diameter of the inner pipe and the inner diameter of the outer pipe; inserting the matched inner pipe into the outer pipe; and mechanically expanding with diameter control the pipes to a preset outer diameter of the multi-layer steel pipe.
Claim 2
Independent Claim
74 words
A method for production of multi-layer gap-less steel pipes comprising matching individual helical welding seam steel pipes of about the same length with a difference of less than about one percent between the outer diameter of the inner pipe and the inner diameter of the outer pipe; inserting the matched inner pipe into the outer pipe; and mechanically expanding with diameter control the pipes to a preset outer diameter of the multi-layer steel pipe.
Claim 3
Dependent Claim
36 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising welding the helical seams of the individual pipes such that at least the adjoining pipe surfaces do not exhibit welding reinforcements.
Claim 4
Dependent Claim
23 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising expanding the outer pipe beyond the yield strength.
Claim 5
Dependent Claim
34 words
The method for production of multi-layer gapless steel pipes according to claim 1 wherein the inner pipe is inserted into the outer pipe without provision for prior geometrical changes after the seam welding step.
Claim 6
Dependent Claim
28 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising descaling the surfaces adjoining in the multilayer pipe before insertion of the pipe.
Claim 7
Dependent Claim
28 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising pretreating the surfaces adjoining in the multi-layer pipe before insertion of the pipe.
Claim 8
Dependent Claim
34 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising keeping peakings at the helical welding seams of the inner pipe lower as compared those of the outer pipes.
Claim 9
Dependent Claim
51 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising cutting the individually produced outer pipes by a certain amount shorter as compared to the inner pipes, where the certain amount corresponds to the amount of relative shortening of the inner pipe resulting from the expansion.
Claim 10
Dependent Claim
33 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising inserting a homogenization foil between the inner and the outer pipe at the pipe ends before the expansion.
Claim 11
Dependent Claim
36 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising subjecting the individually produced helical welding seam pipes before the insertion step to a material and welding seam and/or surface control.
Claim 12
Dependent Claim
34 words
The method for production of multi-layer gapless steel pipes according to claim 1 further comprising finishing the welding seam reinforcements on the inside of the inner pipes before the insertion into the outer pipes.