Pipes and tubular conduits – Distinct layers – Bonded to each other
Reexamination Certificate
1999-08-13
2001-06-19
Hook, James (Department: 3752)
Pipes and tubular conduits
Distinct layers
Bonded to each other
C138S099000, C138S146000
Reexamination Certificate
active
06247499
ABSTRACT:
FIELD
The present invention pertains to corrosion protecting pipe or tubing and associated equipment, such as valves, elbows, tee's, and other equipment typically used with pipe or tubing. More particularly, the present invention pertains to a method of protecting the exposed outer surface of an uncoated pipe or repairing a break in a pipe coating with a corrosion protecting wrap.
BACKGROUND
Pipes, typically used for the transport of fluids such as natural gas and extraction of petroleum crude products, are frequently subject to the harmful effects of corrosion. Such corrosion often occurs when unprotected metal pipes are buried in trenches dug in the ground or used in subterranean well applications.
To protect the exterior surface of pipes against the corrosive effects of soil and/or fluids, various different methods of coating the exterior surface of pipes appear in the prior art. One popular method of coating the exterior surface of pipes involves the application of a fusion bonded epoxy around the outside of the pipe. This fusion bonded epoxy protects the exposed metal on the outer surface of the pipe from the corrosive effects of chemicals in the atmosphere or chemicals contained in soil.
It has been found that because of the brittle nature of a fusion bonded epoxy coating around pipes, the coating is easily broken or cracked if the coated pipe is subject to rough handling. Breaks or cracks in the fusion bonded epoxy coating may allow moisture or corrosive chemicals to migrate through the outer protective layer of fusion bonded epoxy and corrode the exterior metal surface of the pipe. Accordingly, there is a need for a method that will allow for the repair of the corrosion coating placed around pipes after a holiday or break has occurred in the fusion bonded epoxy protective coating.
One prior art method of protecting the exterior surfaces of pipe, tubing, and associated equipment—particularly pipe, tubing, or associated equipment to be placed in a trench or a ditch dug in soil—is to wrap the pipe, tubing, or associated equipment with a fabric which has been saturated with an epoxy. One example of a prior art method and product is a Hempel NAP-WRAP Epoxy 8553. This product is designed for coating the exterior surface of pipelines which have been placed in a ditch or to repair pipe or tubing coatings that have failed in service.
While the Hempel NAP-WRAP Epoxy 8553 product has been effective in some mildly corrosive environments, it will not withstand harsh environments such as those characterized by the presence of either strong acids or high temperatures, (above 225° F.) or both.
Accordingly, there is a need in the art to provide a product which will protect the exterior surfaces of pipes and associated equipment from corrosion in environments which are strongly acidic and which are characterized by a high ambient temperature.
SUMMARY
The present invention provides a system for protecting the exterior surface of pipes against corrosion in environments which are strongly acidic or are characterized by a high ambient temperature.
The inventor herein has found that by using a chemically resistant fabric and selected prior art epoxy resin mixtures, a corrosion barrier system is provided that will maintain protection at temperatures above 225° F., even up to 350° F. Further, the present invention will provide corrosion protection in environments characterized by the presence of a strong acid and/or high temperatures.
The fabric material selected for the wrap and method of the present invention is a non-woven Polyphenylene Sulfide (PPS). In the preferred embodiment, the nonwoven Polyphenylene Sulfide fabric is from 0.010 to 0.050 inches thick.
Before being wrapped around the pipe, the Polyphenylene Sulfide fabric is saturated with a bisphenol A epoxy, lower molecular weight liquid (100% solids) resin. Mixed with the bisphenol A epoxy liquid resin is an epoxy cure agent. In the preferred embodiment, this epoxy cure agent is a cycloaliphatic amine. If desired, fibers and modifiers may be added to the mixture of the liquid epoxy resin and the epoxy curing agent.
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Hook James
ICO, Inc.
Jenkens & Gilchrist a Professional Corporation
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