Pipes and tubular conduits – Plural duct – With spacer and encircling element
Reexamination Certificate
1999-04-21
2001-02-13
Hook, James (Department: 3752)
Pipes and tubular conduits
Plural duct
With spacer and encircling element
C138S121000, C138S125000, C138S127000, C138S131000, C138S149000
Reexamination Certificate
active
06186181
ABSTRACT:
This application is based on and claims the benefit of German Patent Application No. 198 18 167.1 filed Apr. 23, 1998, which is incorporated by reference herein.
1. Background of the Invention
This invention relates to a flexible line pipe as described in the introduction to claim
1
.
For the offloading of intensely-cooled, liquefied natural gas from a delivery vessel to a transport vessel, a thermally insulated line pipe is required that is flexible and has good insulating characteristics at a temperature of approximately −160° C.
DE 25 29 259 A1 describes a line pipe for the transport of liquid or gaseous cooled media between two movable objects floating on the ocean, in which one or more thermally insulated pipelines are oriented parallel to a carrier cable. Fastened to the carrier cable are weighting elements that ensure that the pipeline connects the two objects to one another. In this case, the thermally insulated pipeline consists of two concentric corrugated metal tubes, between which there is a thermal insulation layer based on polyurethane foam.
Apart from the fact that this type of tube is complicated and expensive, it has been shown that the polyurethane foam used as insulation becomes brittle at temperatures below −120° C. and crumbles when the tube system bends, thereby losing a major portion of its insulating properties.
U.S. Pat. No. 4,984,605 A describes a pipeline for intensely-cooled media that consists of two concentric corrugated metal tubes, between which there is an insulation layer. A spiral-shaped spacer lies on the inner tube, and a super-insulation layer is wrapped around the spacer so that a ring-shaped gap remains between the super-insulation layer and the inner tube. The term “super-insulation” is used in technical circles to mean a structure that consists of alternating layers of metal films and films of fleece. The purpose of the ring-shaped gap is to accelerate the evacuation process, in particular in long conduits and pipelines.
The line pipe of the prior art is used for the transport of liquid nitrogen, helium and oxygen. It is very expensive to manufacture because, in spite of the measures adopted, the evacuation process is difficult and time-consuming on account of the high degree of evacuation required.
SUMMARY OF THE INVENTION
The object of the invention is, therefore, to create a line pipe that is flexible and can be manufactured in long lengths and can also be used at temperatures below −100° C. without any loss of its thermal insulating characteristics.
The invention teaches that this object can be accomplished by the features disclosed in the characterizing portion of claim
1
.
The essential advantage of the invention is that the cords wrapped in opposite directions provide good insulation because the contact between them is essentially a spot contact, and the selection of material also ensure a piping system that is stable when bent and has a high vibration fatigue limit.
The fleece material applied in the form of a strip fills up to 90% of the space between the inner and the outer tubes, as a result of which the vacuum can be set to a value between 10
−1
and 10
−3
mbar, because the thermal transmission by convection is reduced on account of the filling of the spaces. The amount of heat admitted into the piping system claimed by the invention is higher than with a conventional high vacuum insulation using super-insulation films, but is much lower than with foam insulation systems.
The costs for the line pipe claimed by the invention are significantly lower than the costs of pipes with conventional high vacuum insulation, but are only insignificantly higher than for a foam insulation.
Additional advantageous configurations of the invention are described in the subclaims.
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Alcatel
Hook James
Sughrue Mion Zinn Macpeak & Seas, PLLC
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