HELICALLY WOUND PIPE AND RELATED METHOD

1 - 11 . (canceled)

12 . A method of manufacturing helically ribbed pipe, the method comprising:

using an elongate composite plastic strip having a base portion having an upper surface and a lower surface, a plurality of ribs extending upward from the upper surface of the base portion, each rib formed by a reinforcement strip within plastic material, the composite plastic strip having a first side and a second side;

helically wrapping the composite plastic strip into a tubular pipe form with the upper surface and the ribs at an exterior of the tubular pipe form and with a first portion of the first side overlapping a first portion of the second side at a helical joint, and, during the wrapping, applying a plastic seam weld between the overlapping first portions for bonding the overlapping first portions;

applying pressure to the overlapping first portions of the first side and the second side to compress the plastic seam weld;

after the application of the pressure, applying a plastic overweld that extends over the overlapping first portions of the first side and the second side and over both a second portion of the first side and a second portion of the second side, wherein the second portion of the first side is adjacent to the first portion of the first side and does not overlap with any part of the second side, and wherein the second portion of the second side is adjacent to the first portion of the second side and does not overlap any part of the first side.

13 . The method of claim 12 , wherein the overlapping first portions of the first side and second side are between a first one of the ribs that is proximate the first side and a second one of the ribs that is proximate the second side, wherein the overweld extends onto a first region of transition from the base portion to the first one of the ribs and onto a second region of transition from the base portion to the second one of the ribs.

14 . The method of claim 13 , wherein the first region of transition is defined by a first thickening of plastic of the base portion and the second region of transition is defined by a second thickening of plastic of the base portion.

15 . The method of claim 14 , wherein the first thickening defines a first exterior outwardly curved surface segment adjacent the first one of the ribs and the second thickening defines a second exterior outwardly curved surface segment adjacent the second one of the ribs.

16 . The method of claim 12 , wherein the plastic overweld is applied so as to bond to each of: an exterior one of the first portions, a part of the plastic seam weld that is external of the overlapping first portions, the second portion of the first side and the second portion of the second side.

17 . The method of claim 16 , wherein the plastic overweld is applied such that a central segment of the plastic overweld has a first thickness and adjacent first and second side segments of the plastic overweld have respective side segment thicknesses, wherein each side segment thickness is at least thirty-five percent larger than the first thickness.

18 . A method of manufacturing a helically ribbed pipe, the method comprising:

using an elongate plastic strip having a base portion having an upper surface and a lower surface, a plurality of ribs extending upward from the upper surface of the base portion, the plastic strip having a first side and a second side;

helically wrapping the plastic strip into a tubular pipe form with the upper surface and the ribs at an exterior of the tubular pipe form and with a first portion of the first side overlapping a first portion of the second side at a helical joint, and, during the wrapping, applying a plastic seam weld between the overlapping first portions for bonding the overlapping first portions;

after the plastic seam weld is applied, applying a plastic overweld that extends over the overlapping first portions of the first side and the second side and over both a second portion of the first side and a second portion of the second side, wherein the second portion of the first side is adjacent to the first portion of the first side and does not overlap with any part of the second side, and wherein the second portion of the second side is adjacent to the first portion of the second side and does not overlap any part of the first side.

19 . The method of claim 18 , wherein the overlapping first portions of the first side and second side are between a first one of the ribs that is nearest the first side and a second one of the ribs that is nearest the second side, wherein the plastic overweld extends onto a first region of transition from the base portion to the first one of the ribs and onto a second region of transition from the base portion to the second one of the ribs.

20 . The method of claim 19 , wherein the first region of transition is defined by a first thickening of plastic of the base portion and the second region of transition is defined by a second thickening of plastic of the base portion.

21 . The method of claim 20 , wherein the first thickening defines a first exterior outwardly curved surface segment adjacent the first one of the ribs and the second thickening defines a second exterior outwardly curved surface segment adjacent the second one of the ribs.

22 . The method of claim 18 , wherein the plastic overweld is applied so as to bond to each of: an exterior one of the first portions, a part of the plastic seam weld that is external of the overlapping first portions, the second portion of the first side and the second portion of the second side.

23 . The method of claim 22 , wherein the plastic overweld is applied such that a central segment of the plastic overweld has a first thickness and adjacent first and second side segments of the plastic overweld have respective side segment thicknesses, wherein each side segment thickness is at least thirty-five percent larger than the first thickness.

24 . The method of claim 18 , wherein a central segment of the plastic overweld is applied to result in a central sement thickness of at least 0.150 inches.

25 . The pipe of claim 18 , wherein a central segment of the plastic overweld is applied to result in a central segment thickness of at least 0.180 inches.

26 . The method of claim 18 , wherein a central segment of the plastic overweld is applied to result in a central segment thickness that is equal to or greater than thirty percent of a combined thickness of the overlapping first portions and the plastic seam weld therebetween.

27 . The method of claim 18 , wherein a central segment of the plastic overweld is applied to result in a central segment thickness that is equal to or greater than fifty percent of a combined thickness of the overlapping first portions and the plastic seam weld therebetween.

28 . The method of claim 18 , wherein a central segment of the plastic overweld is applied to result in a central segment thickness that is equal to or greater than seventy percent of a combined thickness of the overlapping first portions and the plastic seam weld therebetween.

29 . The method of claim 18 , further comprising:

carrying out a pre-heat step prior to application of the plastic seam weld;

after application of the seam weld, applying pressure to the overlapping first portions of the first side and the second side to compress the plastic seam weld; and

after applying pressure, carrying out a secondary pre-heat step, prior to applying the plastic overweld.