Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using disinfecting or sterilizing substance
Reexamination Certificate
2001-01-08
2003-08-12
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using disinfecting or sterilizing substance
C422S001000, C422S006000, C422S012000, C422S032000, C422S040000, C422S123000, C122S379000, C034S403000, C034S404000, C034S410000, C034S437000, C169S005000, C169S011000, C239S104000, C239S105000, C239S106000, C239S108000, C239S112000, C134S011000, C134S022110, C134S026000, C134S034000, C134S037000, C134S042000, C510S247000
Reexamination Certificate
active
06605254
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the fumigation and maintenance of closed systems that are susceptible to microbially influenced corrosion (MIC).
BACKGROUND
The maintenance of systems that corrode over time due to microorganism contamination is a significant challenge due to the proliferation, resilience and adaptability of microorganisms. A large number and variety of systems are susceptible to such degradation, and while a variety of methods have been devised to address these systems, including cleaning and scraping, the need exists for a method that addresses the root causes of the corrosion, and that is capable of safe and effective use in a wide variety of systems, irrespective of the material composition of the system.
Systems manufactured of metals, and metal alloys, are particularly susceptible to damage from microbes. These effects are seen predominately in piping and other enclosed systems, where microbially influenced corrosion and biofouling cause occlusion, leaks, and premature failure of materials of construction. There are several types of bacteria responsible for the deterioration, often with more than one species observed in a pipe sample. These bacteria can be found both in installed systems, and on pipe that has never been in service. Without treatment, these microbes multiply, damaging the system and contaminating its contents. While metal systems are particularly susceptible to corrosion, plastic constructions are also susceptible to microbial degradation, which is enhanced by combinations of factors, including environmental factors, such as temperature and solar radiation. These factors combine with the processes promoted by contaminating microorganisms to foul systems, and lead to system failure.
Microbial damage affects a vast number of enclosed systems, ranging from tanks and vessels to piping systems. Potential applications of this anti-microbial treatment include fire protection sprinkler systems, water purification and delivery equipment, cooling towers, ballast systems, and manufacturing or chemical processing, handling and storage equipment.
Commercially available system maintenance treatment options include flushing systems with liquid disinfectants and cleaning solutions such as glutaraldehyde (U.S. Pat. No. 5,160,047) or glycolic acid solution (U.S. Pat. No. 5,885,364). Liquid disinfectants are limited in their ability to reach every surface in the system since it is difficult to flush thoroughly every branch and upright section of an extensive network of piping. Any bacteria that are not directly exposed to the disinfectant will reproduce.
Gaseous sterilizing agents such as ethylene oxide and chlorine dioxide are known and have been used for fifty years in the medical industry to sterilize medical instruments and equipment. Both chlorine dioxide and pure ethylene oxide are explosive. However, nonflammable sterilant blends with an inert carrier gas are commercially available.
The potential effectiveness of fumigants in a method to fumigate systems that are susceptible to microbially influenced corrosion (MIC) is not known. In particular, ethylene oxide is known to be more effective on porous materials than non-porous. Applicants have discovered that, when used in the methods of the present invention, fumigants, and in particular ethylene oxide, may be effectively employed to uniformly expose the inner surface of a system and penetrate layers of corrosion products and/or microorganism growth present on the system inner surfaces to reach the underlying microorganisms of the type that influence corrosion. The method has a wide range of applications but is particularly useful for mitigating MIC in fire protection sprinkler systems.
SUMMARY OF THE INVENTION
The present invention relates to a method of fumigating a closed system containing articles or means in which aqueous media is contained or through which aqueous media flows, which method comprises exposing the surfaces of the article or means or to an effective amount of a fumigant for an effective time of exposure.
More particularly, the invention relates to a method of fumigating a closed system containing articles or means in which aqueous media is contained or through which aqueous media flows, which method comprises evacuating the system; introducing an effective amount of a fumigant; exposing the system to the fumigant for an effective time of exposure; and removing the fumigant.
In a preferred embodiment of the method of the invention, the fumigant comprises a non-flammable blend of ethylene oxide and an inert carrier gas.
In another preferred embodiment, the method comprises humidifying the system to about 30-90% relative humidity, preferably about 50 to about 80% relative humidity prior to introducing the fumigant.
In still another preferred embodiment, the method comprises adding heat to the system to accelerate the biocidal activity of the fumigant.
In yet another preferred embodiment, the method comprises exposing the system to the fumigant under subatmospheric pressure, preferably between about 0.5 and less than 1 atm.
DETAILED DESCRIPTION OF THE INVENTION
The systems treated by the present method comprise articles or means having outer and inner boundaries wherein the inner boundary defines a space. This space is bounded by the inner surfaces of the article, which space may extend directionally and define passageways through which fluids may flow. Said inner surfaces may be of any configuration such as curvaceous or flat and illustratively but not limited to forming a cylindrical or tubular space, or a polygonal space such as triangular or rectilinear space. The articles enclosing these spaces are typically designed to comprise one or more openings providing for the introduction and elimination of said fluids. Exemplary systems include enclosed articles (closed systems) such as tanks, vessels, piping, conduits, couplings, valves, and tubing of all shapes and sizes.
The systems are constructed of a variety of materials by any known process including extrusion, molding, casting, milling, annealing, thermoforming, cutting, drilling, bending, etc. Material properties related to the use of the articles are generally characterized by mechanical strength, chemical resistance, durability, and resistance to heat, light, oxygen, and moisture. In particular the materials comprising the articles are typically chemically resistant to the fluid(s) that contact the inner surfaces of the article, including the fumigants disclosed herein to treat the surfaces at the conditions of exposure. Exemplary materials include metals and plastics. Illustrative metals are copper, iron, steel, aluminum, and alloys thereof and coated metals such as zinc coated steel. Illustrative plastics include elastomers, polyvinyl chloride (PVC), chlorinated PVC, polybutylene, nylon, polyurethane, polyolefin, polycarbonate any of which may incorporate additives including fillers, pigments, plasticizers, antioxidants, flame retardants and UV light stabilizers.
Microbially influenced corrosion (MIC) refers to degradation or corrosion as a result of coming into contact with, or providing suitable growth conditions for, microorganisms that promote and/or catalyze material corrosion processes. The types of bacteria known to cause MIC are low nutrient bacteria (LNB), iron related bacteria (IRB), sulfate reducing bacteria (SRB) and acid producing bacteria (APB). They may also be referred to as metal-damaging microbes.
As used herein the term “fumigate” means to subject to fumes in order to destroy, neutralize or inhibit the growth of microorganisms that influence corrosion. Fumigation of that results in a reduction of at least two logs, and preferably three or more logs, of the contaminating microorganisms is desirable.
The term “fumigant” means an agent in vapor form that is toxic to microbes that influence corrosion. Suitable fumigants include alkylene oxides, chlorine dioxide, fluorine dioxide, ozone, hydrogen peroxide, methyl bromide and the like for an amount of time sufficient to fumigate said systems
Aguilera Anthony Mark
Bitney Ronald Gordon
Conviser Stephen Alan
Decaire Barbara Ruth
Allied-Signal Inc.
Chess Deborah M.
Chorbaji Monzer R.
Szuch Colleen D.
Warden, Sr. Robert J.
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