Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2001-11-07
2004-08-03
Bell, Bruce F. (Department: 1746)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S196190, C204S196210, C204S196230, C204S196240, C204S196300, C204S196310, C204S196360
Reexamination Certificate
active
06770177
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to compressor tanks, and more particularly to corrosion protection systems for compressor tanks.
BACKGROUND OF THE INVENTION
Corrosion is a concern for compressor tanks. Compressor tanks are commonly made from metal, or other materials that are susceptible to corrosion. The threat of corrosion is greatest near the bottom of a compressor tank where condensation can accumulate. The condensate within the tank can corrode the interior surface of the tank wall and reduce the wall thickness of a portion of the tank. The contents of a compressor tank are under pressure. If the wall thickness of the tank is decreased and the tank wall is weakened, the tank may fail.
Compressor tanks are generally equipped with a let down valve to periodically drain condensate moisture is a gas and is not drained. It can “escape” when the valve is opened from the tank, but a tank rupture may still occur if the let down valve is not used sufficiently frequently. Additionally, it is difficult to determine the amount of corrosion that has occurred in a tank. Even if the condensate is drained from a tank, a significant amount of corrosion may have occurred before the draining. Further corrosion may cause a tank rupture.
SUMMARY OF THE INVENTION
The invention comprises a corrosion protection device for an air compressor tank to prevent tank failures. A feature of the corrosion protection device is to inhibit corrosion of the tank caused by condensate that has accumulated in the tank. The tank has a tank wall defining an enclosed interior volume, and a tank opening in the tank wall. The corrosion protection device comprises a plug that is removably positioned in the tank opening to close the tank and seal the interior volume. A relief passage extends through the plug, and at least a portion of an anode closes the relief passage. The anode, plug, and tank are all coupled in an electrically conductive relationship.
The corrosion protection device is disposed near the bottom of the tank where condensate is most likely to accumulate. The plug has a let down valve that may be opened to release condensate and pressure from within the tank. If the let down valve is not utilized sufficiently frequently, condensate may accumulate and corrode the materials it comes in contact with. The anode has a lower redox potential than the tank, and corrodes at a faster rate than the tank corrodes. Compressor tanks are generally made of steel, and the anode may be made of magnesium. The anode is more likely than the tank to lose electrons and corrode, so the anode inhibits corrosion of the tank by corroding before the tank corrodes. After corrosion has consumed a sufficient portion of the anode to open the relief passage, the moisture and pressure within the tank are released through the relief passage. A consumed anode may be replaced by a new anode, and the tank may then be reused.
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M.C. Miller, Corrosion of Buried Metals and Cathodic Protection, Petroleum Engineering, Apr., May, Jun. 1944, pp. 1-10.
Corrosionsource.com-Cathodic Protection, http://www.corrosionsource.com/learingcenter/cathodic.htm, Oct. 20, 2000, pp. 1-5.
Corrosion Mechanisms, Chapter 2, http://www.corrpro.com/rcs/datasheets/primer/chapter2.pdf, Chapter2.pdf, Oct. 16, 2000 14:13, pp. 3-8.
Thomas C. Fisher, Basic Meter Hookups, Columbia Gas of Ohio, pp. 11-16, Fitzgerald, III, John H., Fundamentals of Corrosion, The Hinchman Company, pp. 17-28.
Keller Charles Tillman
Lewis William M.
Bell Bruce F.
Ingersoll-Rand Company
Michael & Best & Friedrich LLP
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