Multiwall pipe lip seal joint
An elastomeric lip seal joint for sealing the inner liner and grout layers when joining two sections of multiwall pipe having an outer steel casing and an inner liner. The ring-shaped lip seal joint comprises a gasket with insulating material completely covering its outer surface. The insulating material is capable of shielding the gasket from the heat produced when the sections of outer steel casing are welded together. The use of the lip seal joint simplifies the process of joining sections of multiwall pipe. Each side of the lip seal joint is inserted into one of the annular voids at each end of the pipe, thereby sealing the inner liner and grout. A single circumferential weld then joins the outer steel casing. The gasket remains intact during the welding process due to the presence of the insulating material.
1. A ring-shaped member for use in joining lengths of multiwall pipe to form pipeline systems for transporting pipeline fluids, each length having two ends, a steel outer casing, an inner liner having a uniform outer diameter, and an annulus holding a grout layer, the annulus having a height between the outer casing and the inner liner and an annular void having a width at each of the ends, the member comprising:
an elastomeric gasket having an outer surface and an inner surface;
insulating material dimensioned to completely cover the outer surface of the gasket; and
means for affixing the insulating material to the outer surface of the gasket;
the member having a first side and a second side and a uniform inner diameter corresponding to the uniform outer diameter of the inner liner and further having a height corresponding to the height of the annulus and a width equal to twice the width of the annular void at each of the ends of the lengths of pipe, the member being fabricated so that the first side fits into the annular void at the end of a first length of multiwall pipe and the second side fits into the annular void at the end of a second length of multiwall pipe, thereby sealing the inner liner at the ends of the first length of pipe and the second length of pipe, the member being completely enclosed by abutting ends of the outer casing and the inner liner.
2. The ring-shaped member of claim 1 which further comprises a circumferential, triangular, centrally-located open notch cut into the inner surface of the gasket.
3. The ring-shaped member of claim 2 which further comprises a strip of stiffening material mounted inside the notch.
4. The ring-shaped member of claim 1 , wherein the elastomeric material is selected from the group consisting of rubber, neoprene, Buna-N, silicone, and polyurethane.
5. The ring-shaped member of claim 1 , wherein the insulating material is fabricated from a material selected from the group consisting of titanium, flexible ceramics, steel, and coated fiberglass.
6. The ring-shaped member of claim 1 , wherein the means for affixing the insulating material to the outer surface of the gasket is a bonding agent selected from the group consisting of neoprene bonding agents, nitrite bonding agents, anaerobic activators, and rubberized adhesives.
7. The ring-shaped member of claim 1 , wherein the means for affixing the insulating material to the outer surface of the gasket is selected from friction-mounting and formation thereon.
8. A method for joining lengths of multiwall pipe having two ends, a steel outer casing, an inner liner having an outer diameter, and a uniform annulus holding a grout layer, the annulus having a height between the outer casing and the inner liner and an annular void having a width at each of the ends, the method comprising the following steps:
(a) axially aligning a first length of multiwall pipe and a second length of multiwall pipe, end-to-end in a spaced-apart relationship;
(b) positioning between the first length of pipe and the second length of pipe a ring-shaped member having a first side and a second side and a uniform inner diameter corresponding to the uniform outer diameter of the inner liner, the member comprising an elastomeric gasket having an outer surface and an inner surface, and further having insulating material affixed to and completely covering the outer surface of the gasket;
(c) inserting the first side of the member into the annular void at the end of the first length of pipe;
(d) inserting the second side of the member into the annular void at the end of the second length of pipe;
(e) ensuring that the ring-shaped member is completely enclosed within the annular voids by the abutting ends of the outer casing and the inner liner;
(f) welding together the outer casing at the end of the first length of pipe and the second length of pipe; and
(g) having the member be supported by the outer casing of the pipe.
9. The method of claim member of claim 8 wherein the ring-shaped member further comprises a circumferential, triangular, centrally-located open notch cut into the inner surface of the gasket.
10. The method of claim 9 , which further comprises mounting a strip of stiffening material inside the notch of the ring-shaped member.
11. The method of claim 8 , wherein the ring-shaped member is fabricated from an elastomeric material selected from the group consisting of rubber, neoprene, Buna-N, silicone, and polyurethane.
12. The method of claim 8 , wherein the ring-shaped member has an insulating material fabricated from a material selected from the group consisting of titanium, flexible ceramics, steel, and coated fiberglass.
13. The method of claim 8 , wherein the insulating material is affixed to the outer surface of the gasket by a bonding agent selected from the group consisting of neoprene bonding agents, nitrite bonding agents, anaerobic activators, and rubberized adhesives.
14. The method of claim 8 , wherein the insulating material is affixed to the outer surface of the gasket by means selected from friction-mounting and formation thereon.