Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-12-17
2004-01-06
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S310000, C156S304300, C525S239000
Reexamination Certificate
active
06673193
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the art of coating and lining fluid containers and conduits, and more particularly concerns systems and methods for chemically joining and sealing coatings and linings together for the purpose of coating and lining fluid containers and conduits.
2. Description of Related Art
Waste water and sewerage are frequently conducted through fluids conduits made of concrete. In some applications, the conduits are made of metal. Sewer systems frequently have reservoirs, containers and ponds, such as settling ponds which also are made of concrete and sometimes metal. Sewerage and waste water often contain material that is highly corrosive, especially with respect to concrete and metal. The closed systems that constitute most sewerage systems in use presently create anaerobic conditions ideal for the proliferation of anaerobic bacteria that result in hydrogen sulfide. Consequently, waste water pipes, sewage pipes, reservoirs, containers and ponds frequently are the subject of substantial corrosion and deterioration. The addition, corrosive material resulting from the digestive by-products of organisms existing within the waste water and sewer systems cause substantial deterioration of the concrete and metal conduits.
As used herein, the terms “conduits” and “pipes,” are intended to include not only conduits and pipes, but also box tunnels and culverts, reservoirs, containers and ponds as discussed above. Such “conduits” and “pipes,” as those terms are used herein, can include, for example, settling or processing “ponds” at sewage processing plants, back-up reservoirs and, in general, building structures involved with such processing.
The deterioration that occurs in such conduits and pipes frequently takes the form of physical decay of the walls of the conduits and pipes, so that the thickness of the walls is reduced. Significant amounts of the concrete or metal can be removed or corroded away over the years. In many instances, sewer and waste water conduits and like structures have walls so thin that the conduits have collapsed under the weight of traffic passing over them, and it has been reported that people have stuck their arms through them with relative ease.
Another undesirable effect of the corrosion and deterioration is that in the weakened condition that thin walls have, the walls crack more easily, resulting in leaks in the sewer system. Such leaks undermine the soil or prepared beds surrounding the concrete or metal pipes. Further, such leaks may contaminate the aquifer, pollute the waterways, and come to the surface to make the environment above unpleasant, as well.
Some of the more common corrosive materials within sewer conduits are sulfuric acid and hydrogen sulfide, which can turn into sulfuric acid under the conditions frequently found in sewer systems. Their corrosive effects may be readily appreciated. Sewer conduits normally have an anaerobic slime deposit along the wall of the conduit which is submerged below the liquid line or level. Various metal sulfates are among the more common ingredients of this anaerobic deposit. In the substantially liquid waste water, the sulfates reduce to sulfide ions, which combine with the hydrogen in the waste water to outgas above the liquid level as hydrogen sulfide.
Hydrogen sulfide, per se, can be highly corrosive to metals, of which some sewer pipes are made. Many concrete pipes have metal, as, for example, steel reinforcing ribs, beams and like support structures, which are sometimes called “rebar.”
Oxygen from the air intakes in the sewer system, such as manholes, as well as oxygen from water condensing on the upper portions of the interior surfaces of the conduit wall which are not in contact with the liquid being conducted, interacts with bacteria within the conduit above the liquid level. The bacteria above the liquid level thus produces more hydrogen sulfide. Oxygen from the liquid and condensing from the water in the air reacts with the hydrogen sulfide gas to create highly corrosive sulfuric acid. The acid reacts with the calcium hydroxide in the cement of the concrete conduit, producing gypsum or calcium sulfate, which has been described as a soft corrosion product. The gypsum drops off the interior of the wall itself, making the wall thinner and substantially weakened. In this manner, whole chucks of the concrete wall are removed or vanish, reducing the thickness and strength of the wall.
Restoring such damaged and weakened conduits and pipes in the past has been accomplished primarily through two fundamental methods. In one basic modality, the concrete conduits are entered and fresh concrete is troweled or applied onto the walls to build the thickness back to the original dimension. This method is somewhat problematic in that applying concrete on the roof of the conduit requires special efforts and time. Frequently, such as in sewer conduits, for example, the repair must be performed within a specified time window. Usually, sewer conduits have a relatively lower flow rate or level during the hours between midnight and the normal waking hours of around seven in the morning. After the normal waking hours, most sewer conduits are so full that entry into the conduit and any repair are not possible.
A second modality involves a process of digging from the top surface down to the weakened conduit. The earth around the weakened conduit is excavated, and a layer of concrete of suitable thickness is poured around the weakened conduit to, in effect, provide a new conduit encasing the old, crumbling sewer pipe. This method has special problems, as well. For example, most such pipes are underneath roadways and streets. Excavating down to the sewer pipe requires removing the surface road or street and diverting traffic often for weeks at a time. The amount of concrete required to encase the old pipe is substantial. The manpower required for excavating, concrete pouring and road and street restoration is substantial, as well. Both in time and material, such repair or restoration is expensive, and the disruption to street traffic is costly to the public.
Other modalities exist, such as for example a method called “slip lining,” in which new pipe is inserted within the old, crumbling pipe to strengthen the pipe walls. Such methods reduce the diameter of the pipe or conduit and create problems with connecting lateral pipes joined to the pipe being repaired or restored.
Many of the methods used in the past result in a restored conduit which has a surface facing the effluent made of the same material that deteriorated before. This problem has been addressed by coating or lining the interior facing surfaces after restoration of the conduit, but such liners or coating have met with only varying levels of satisfaction.
In the past, many such coating have been made of material in which small pin holes develop, through which the corrosive substance seeps to corrode the concrete so coated “behind” the lining or coating. The corrosion taking place behind the liner or coating not only deteriorates the concrete or metal conduit itself, and the lining or coating breaks loose from the conduit to add to the clogging within the conduit.
It has been known in the past to provide lining for the interior surfaces of such conduits and pipes. See, for example, U.S. Pat. No. 4,792,493 issued to Vernie L. Belcher and myself, and U.S. Pat. No. 5,268,392 issued to myself. Such linings greatly enhance the ability of the conduit to resist the corrosive effects of the many acids, caustics, toxins and organic material common in waste water and sewer systems.
In many situations, however, liners are applied to the interior of concrete pipe sections prior to inserting in the ground and connecting with other pipe sections to form the conduit. In one conventional technology, the liners are provided in sheets, and can be secured to the concrete by ribs having a “T” cross-section embedded in the concrete. Such sheets are normally in widths of approximately four feet. Multiple sheets
Aftergut Jeff H.
Goff John L.
Hall Priddy Myers & Vande Sande
Linabond Inc.
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