Chemistry: physical processes – Physical processes – Crystallization
Reexamination Certificate
2002-05-23
2003-12-16
Lefkowitz, Edward (Department: 2856)
Chemistry: physical processes
Physical processes
Crystallization
C073S073000, C073S029010, C116S206000, C096S117500
Reexamination Certificate
active
06663679
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
None
FEDERALLY SPONSORED RESEARCH
Not Applicable
SEQUENCE LISTING, TABLE OR COMPUTER PROGRAM
Not Applicable
FIELD OF THE INVENTION
The present invention is directed to the field of humidity monitoring devices.
BACKGROUND OF THE INVENTION
Humidity, or the level of moisture in an environment, is a critical concern for many applications. There are many systems and materials that can be damaged by the presence of water. Accordingly, it is important to have a method to determine the presence of moisture and even small quantities of water vapor at varying levels of humidity. Additionally, many piping systems contain fluids, principally composed of water, that have a deleterious effect on the piping system itself or on other components or materials external to such a system.
Very often, in a fluid containing system, the corrosive fluid in the system is water. Even in small quantities, due to its formation as a vapor, water can lead to corrosive effects. Water presents a great threat to most forms of carbon steel and some other metal surfaces by increasing surface corrosion. Moisture can negatively affect various chemical, mechanical, and electronic processes and components, as well as the operation of some forms of equipment, if allowed to reach sufficient levels. Even low moisture levels can produce substantial damage. In worst-case examples, where there is a high humidity condition, over a sufficiently long duration, valuable product, processes, and equipment can be destroyed, or rendered useless.
Water is a component of a corroding system and will have a continual action on materials meant to contain it. At other times, ambient moisture needs to be prevented from reaching into a sensitive area.
The present invention provides a method of indicating, as part of a monitoring system, that water has escaped from its containment system or that water has entered a moisture sensitive area.
Monitoring the humidity level in such environments therefore becomes of great concern to both manufacturers and users of such humidity sensitive products and equipment. As a result, various methods of indicating humidity exist, both electronic and chemical.
In developing a humidity sensor, it is important that such a sensor be flexible in its application, error-free (such as avoiding false negative responses), persistent, unequivocal, simple in design and inexpensive to manufacture.
In use to detect the entry of moisture, the present invention may be in the form of a self-contained unit that can be placed in view inside a sensitive area. If it is not possible to have the unit in view, it may need to be incorporated within the walls containing the sensitive components. In such a case, a viewing window would be part of the detection unit. In piping systems, the present indicator invention would typically be part of a fitting mounted into the walls of the pipe.
U.S. Pat. No. 6,131,433 to the author of the present invention (Duncan) describes a corrosion monitoring device and more particularly to a self contained, disposable corrosion monitor for a fluid containing system, which indicates a breakthrough of the integrity of the wall of the system due to the corrosive action of a fluid in the fluid containing system. More particularly, the present invention may be incorporated to provide the indication that water has broken through, when used in a system where the fluid contains water.
Failures of metal pipes, tanks and other fluid enclosures due to the deterioration of their inner wall surfaces are all too common occurrences; currently causing over 10 billion dollars annually in replacement costs alone. While some corrosion induced metal failures may create a great and unexpected financial loss due to replacement cost, down time and water damage, more severe failures of high temperature and high pressure pipes and vessels may result in explosion, extensive physical damage, severe injury and human casualty. Effective corrosion monitoring is therefore greatly desired from such a production, health, environmental, process reliability, economic and liability viewpoint.
Corrosion of metal surfaces is a continuous and generally non-stoppable electrochemical process, which is well known and documented. Given sufficient time, metal failures are inevitable where fluids and metal meet and interact, and where at best, the negative physical effects of corrosion can only be minimized, not eliminated.
Due to the complex interaction of chemical, electrical and mechanical influences which determine the degree of activity of a corrosion environment, and the fact that such corrosion activity often widely varies at different locations within the same fluid environment, there is the need to monitor as many individual locations in a given piping system, tank, pressure vessel or reactor vessel as possible. The inability to monitor the corrosion activity at multiple locations within a piping system is frequently a cause of failure, since a single monitoring point,not representative of the corrosion in the entire piping system, may produce an erroneous prediction of service life and service failure.
Chemical and electrical corrosion inhibitors and other substances exist to help reduce corrosion and are often relied upon exclusively to safeguard piping and other metal components. The use of such corrosion inhibitors does not preclude the need for corrosion monitoring, however, since actual results of anti-corrosion agents vary widely, thereby making it necessary to regularly verify their efficiency and proper application.
A wide variety of corrosion monitors and procedures exist in the literature and in current use with the purpose of measuring the corrosive nature of a fluid or fluid stream against a specific metal surface. These devices are described in U.S. Pat. No. 6,131,433, incorporated herein by reference. Many monitoring devices, therefore, find limited actual field use, provide unsatisfactory corrosion monitoring coverage due to the limited number of sensors or probes installed and provide little benefit to all but the most critical of applications.
Ultrasonic testing is well recognized for providing extremely accurate remaining wall thickness measurements for any metal structure, but typically serves as a survey or an instantaneous measuring tool rather than a long term monitoring device. It has a disadvantage of being a temporary measurement instrument, is expensive, and requires an experienced operator and careful analysis and manipulation of the resulting data, as well as periodic access to the exact same area of the pipe surface for reevaluation.
DESCRIPTION OF RELATED ART
Current humidity indicators work on the basis of some chemical change occurring within a viewable material to produce a color change within that same material. Materials commonly used are based around some form of silica gel or clay or cobalt chloride. Some materials exist just as indicators of moisture, while others provide a desiccating service and also change color only after their ability to absorb moisture has been exceeded, and moisture level increases. Prior art humidity indicators vary depending upon the physical shape and differentiation in indicating ability, such as providing indication in 10% or 20% increments, although they all operate on a basic color change within a chemical compound given a certain humidity level.
The disadvantage of such indicators is that they produce a very faint color change typically varying from a light blue when new and completely dry to a faint pink or lavender when they absorb moisture. Some products offer a mildly stronger color change, or different beginning and final colors. Because the colors are faint and the change is minimal, it would not be immediately noticeable in an industrial environment without some form of prompting to view it closely. It would be unlikely to see such a color change from more than 10 feet away.
A further disadvantage of such products is that, if encountering an actual water condition and not simply a high degree of humidity, they will ty
Myers Joel D.
Myers & Kaplan LLC
Williamson III Thomas R.
LandOfFree
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