US2212826A - Refrigerating system - Google Patents

Description

Patented Aug. 27, 1940 v UNITED STATES REFRIGERATING SYSTEM No Drawing. Application October 25, 1939, Serial No. 301,228

Claiins.

A. This invention relates to processes of refrigeration for systems containing iron and copper parts and utilizing a halogenated hydrocarbon refrigerant.

B. In refrigerating systems which use halogenated hydrocarbons such as methyl chloride and dichlorodifiuoromethane as refrigerants a phenomenon is observed which is called copper plating. Parts of the system which are made of non-cuprous metals, notably the moving parts such as pistons and valves, become coated with a layer of copper. This coating may proceed to the point where the efiiciency of the apparatus is materially decreased or tothe point where the 16 apparatus may be unable to function. In these systems mineral oil is generally used as a lubricant and it has been observed that much of the plating occurs on the portions of the apparatus which need lubrication or which are in constant 20 contact with the lubricant. This has led to the Y theory that copper from the tubes or otherportions of system, which are formed of that metal or of alloys thereof, is dissolved or suspended in the lubricant, or mixtures of the lubricant and refrigerant, and deposited on those parts.

C. Regardless of the manner in which itoccurs, however, it is an object of this invention to inhibit copper plating in refrigerating systems of the type described.

= D. The objects of the invention-are accomplished, generally speaking, by including in the system a.small amount of picolinic acid. The picolinic acid can be added with successful results to the lubricating oil which is used in the system. E. Although the manner in which picolinic acid functions as an inhibitor of copper-plating is not clearly understood, it is thought that the copper in the parts of refrigeration systems constructed of this metal, forms a chelate compound with picolinic acid producing a relatively insoluble, adherent film on the metallic surface. The plating of the copper from the relatively small amount of the complex that may be in solution is probably prevented by the formation of a similar chelate iron complex on the iron and steel surfaces where the plating would normally occur in the absence of picolinic acid. However, the applicants do not wish to be bound by any 50 particular theory of operation.

F. The following example illustrates, but does not limit the invention; the plcolinic acid being used in any amount which is necessary to produce optimum results.

Example od of time which is suflicient to produce objectionable copper plating in systems not containing picolinic acid and it was found that copper plating had been entirely prevented. It has been demonstrated that additions of picolinicacid from 0.05% to 1.0% based on the weight of the lubricant employed are suflicient to inhibit or to totally prevent copper plating.

'G. Although copper plating has occurred in household and some industrial refrigerating units, it has been more bothersome in large units employing heavy duty compressors. This has to some extent reduced the application of halogenatedhydrocarbon refrigerants in the heavy duty field. By this invention the objection to halogenated hydrocarbon refrigerants in the heavy duty field is removed.

H. As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A process of refrigeration which comprises condensing and evaporating a, halogenated hydrocarbon in the presence of a mineral oil containing picolinic acid. a

2. The process of claim 1 in which the mineral oil contains from 0.05% to 0.1% of pieolinic acid.

3. The process of claim 1 in which the mineral lubricating oil contains about 0.1% of picolinlc acid.

4. A refrigerating system containing. iron parts, copper parts, a halogenated hydrocarbon refrigerant, a lubricating oil, and picolinic acid.

5. The method of inhibiting copper plating in a refrigerating system containing a halogenated hydrocarbon refrigerant which comprises adding picolinic acid to the system.

FREDERICK B. DOWNING. WILLIAM H. MARKWOOD, JR.