Pipes and tubular conduits – Flexible – Braided – interlaced – knitted or woven
Reexamination Certificate
2000-06-05
2002-10-08
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Flexible
Braided, interlaced, knitted or woven
C138S124000
Reexamination Certificate
active
06460575
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to novel thermoplastic or thermoset pipes which can withstand a varied range of internally generated and/or applied pressures for utilization within, primarily, underground liquid and gas transport systems. Such pipes are improvements over standard metal (i.e., steel, lead, and the like) pipes due to construction costs, shipping costs, implementation costs (particularly underground), flexibility (and thus modulus strength allowances) to compensate for underground movements (i.e., earthquakes and tremors), non-rusting characteristics, reduced crack propagation possibilities, and ease in manufacture. Such pipes are preferably reinforced with specific textile reinforcement materials that permit a lower thickness of plastic to be utilized than is generally required to withstand high pressure situations and also serve to prevent propagation of any cracks which may develop within the thermoplastic or thermoset materials. Such pipes exhibit an elongation at break in relation to that provided by the textile reinforcement and not with regard to the same type of elongation at break characteristic for the thermoplastic or thermoset composition.
BACKGROUND OF THE INVENTION
Underground transport of liquids and gases has been utilized for many years. Such underground transport has proven to be the most efficient and safest manner in which to transport potentially explosive, flammable, and/or toxic liquids (such as crude oil, for example) and gases (such as methane and propane, as examples) long distances. The principle method followed to provide such long distance underground transport has been through metal tubes and pipes. In the past, the utilization of metals (such as steel, copper, lead, and the like) was effective from cost and raw material supply perspectives. However, with the population growing throughout the world and the necessity for transporting liquids and gases to more remote locations increases, the continued utilization of such metal articles has become more and more difficult for a number of reasons. Initially, the production of such metal tubes and pipes must be undertaken through high-temperature production methods at specific foundries which are normally located a substantial distance from the desired installation site. Such off-site production thus requires transport of cumbersome metal articles to the installation location and then subsequent placement into already-dug channels. These procedures are, again, difficult to follow since metal articles are rather heavy and must be connected together to form the desired pipeline. Additionally, in order to reduce the number of connections between individual pipes, longer metal pipes could be formed, which adds to the complexity with an increase in required welded connections. Further problems associated with metal pipes and tubes include, without limitation, the potential for rusting (which may contaminate the transported liquid or gas), the low threshold of earth-shifting which could cause a break within the pipeline, and the difficulty in replacing worn out metal pipes in sections, again due to the metal pipe weight, metal pipe length, and connection welds. These break problems have proven to be extremely troublesome in certain geographic areas which are susceptible to earthquakes and tremors on a regular basis. When such unexpected quakes have occurred in the past, the metal gas and liquid pipelines have not proven to be flexible enough to withstand the shear forces applied thereto and explosions, leaks, or discontinued supplies to such areas have resulted. These metal articles have remained in use because of their ability to withstand high pressures. Furthermore, although such metal pipes are designed to withstand such high pressures (i.e., above 80 bars, for instance), once a crack develops within the actual metal pipe structure, it has been found that such cracks easily propagate and spread in size and possibly number upon the application of continued high pressure to the same weakened area. In such an instance, failure of the pipe is therefore imminent unless closure is effectuated and repairs or replacements are undertaken.
Although there is a need to produce new pipelines to remote locations around the world, there is also a need to replace the now-deteriorating pipelines already in use. Aging pipelines have recently caused great concern as to the safety of utilizing such old articles. Unexpected explosions have occurred with tragic consequences. Thorough review and replacement of such old metal pipes is thus necessary; however, due to the difficulties in determining the exact sections of such pipelines which require replacement, there is a desire to completely replace old pipelines but following the same exact routes. Again, due to the difficulties noted above, there is a perceived need to develop more reasonable, safer, longer-lasting, easier-to-install, non-rusting, non-crack propagating, and more flexible pipeline materials. To date, there have been some new thermoset or thermoplastic articles which are designed to withstand rather low pressure applications (i.e., 20 bars or below) and which include certain fiber-wound reinforcement materials (including fiberglass, polyaramids, polyesters, polyamides, carbon fibers, and the like). However, the resultant articles do not include specific textile reinforcements (they are fibers wound around specific layers of plastic material) and thus are difficult and rather costly to produce. Furthermore, such fiber-wound materials cannot be easily produced at the pipe installation site again due to the complexity of creating fiber-wound reinforcement articles subsequent to thermoplastic or thermoset layer production. Additionally, with such off-site production, transport and in-ground placement remain a difficult problem. Thus, although some improvements have been provided in the past in relation and in comparison to metal pipes and tubes, there simply is no viable alternative presented to date within the pertinent prior art which accords the underground liquid and gas transport industry a manner of replacing such high pressure metal articles.
OBJECTS OF THE INVENTION
It is thus an object of this invention to provide such a viable alternative method for replacing or overcoming the shortcomings and difficulties of high pressure (i.e., from about 20 to about 100 bars) underground metal pipes and tubes. Another object of this invention is to provide a suitable fabric reinforcement system which permits a relatively low amount of thermoplastic or thermoset composition to be utilized in order to produce a pressure-resistant thermoplastic pipe article. Yet another object of this invention is to provide an interlocking mechanism to best ensure the textile reinforcement layer remains in place during and after introduction of the outer thermoplastic or thermoset layer. Still another object of this invention is to provide a suitable simplified method of producing such a textile-reinforced thermoplastic pipe article.
SUMMARY AND BRIEF DESCRIPTION OF THE INVENTION
Accordingly, this invention encompasses a pipe comprising at least two distinct layers of thermally manipulated polymeric material and at least one layer of textile reinforcement material, wherein said textile reinforcement material is sandwiched between said two distinct layers of said thermally manipulated polymeric material, wherein the elongation at break exhibited by such a pipe is limited solely to the elongation at break exhibited by said textile reinforcement material, and wherein said textile reinforcement material exhibits an elongation at break of at most 20%, preferably at most 15%, more preferably at most 10%, and most preferably at most 6%. Preferably said pipe is constructed to withstand at least 100 bars of internal pressure before exceeding the elongation at break limit. An alternative yet also preferred embodiment is a pipe which exhibits at most 20 bars of pressure of internal pressure before exceeding the elongation at break limit and a wall thickn
De Meyer Willy
Gilpatrick Michael W.
Brinson Patrick
Milliken & Company
Moyer Terry T.
Parks William S.
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