Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-01-26
2003-09-30
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036300, C428S036400, C428S035700, C428S057000, C428S220000, C428S332000, C428S334000, C428S335000, C428S336000, C428S339000
Reexamination Certificate
active
06627281
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to novel thin-walled thermoplastic or thermoset pipes of at most 5 millimeters in thickness which can withstand a varied range of internally generated and/or applied pressures up to at least 5 bars, preferably at least 20 bars, for utilization within, primarily, liquid 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 higher 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 lower 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.
Of greater concern, however, is the fact that such lower pressure fiber-wound reinforced pipes must exhibit a pipe wall thickness of at least 6 millimeters. This requirement is primarily due to the fact that production of such lower pressure articles is necessarily accomplished at higher temperatures to effectuate proper adhesion between the fiber-wound reinforcement component and the thermoplastic or thermoset resin. Without such adhesion, the reinforcement layer does not remain in proper contact with the resin and therefor cannot provide the requisite limiting elongation characteristics desired. Thus, higher temperatures (above about 170° C., for example) must be utilized during pipe production to provide such adhesion. However, at such high temperatures, the resin component is highly amorphous and thus exhibits little or no structural integrity. The utilization of fiber-wound reinforcement materials requires the actual wrapping of the target resin in specific configurations in order to provide the needed reinforcement properties. Such wrapping itself requires that a certain degree of tension be applied to the fiber-wound material (and thus to the resin component as well) during application. As such tensioning and wrapping must occur during high temperature exposure (again, for adhesive reasons), the lack of structural integrity (particularly with very low thicknesses of below about 6 millimeters) of the amorphous resin component thus results in the impossibility of applying such fiber-wound materials to the resin component to the extent that such materials provide the desired high elongation and thus pressure resistance effects. Considering the need to reduce cost in resin components, the ability to utilize lower amounts of such potentially expensive thermoplastics or thermosets is of great importance. With that in mind, the ability to utilize extremely thin-walled resin pipes which exhibit relatively high (and unexpected) pressure resistance properties is of great interest and need. To date, however, as discussed above, there have been no lower pressure (i.e., between 1 and 80 bar pressure resistance, and particular
Cole Elizabeth M.
Milliken & Company
Moyer Terry T.
Parks William S.
LandOfFree
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