Refrigeration – Processes – Lubricant handling
Reexamination Certificate
2003-01-08
2004-06-29
Jiang, Chen Wen (Department: 3744)
Refrigeration
Processes
Lubricant handling
C062S475000, C062S195000
Reexamination Certificate
active
06755029
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
Ammonia (NH
3
) is a commonly used chemical prevalent in many industrial processes throughout the world. Ammonia may also be naturally occurring and is familiar to most of us as a mild irritant in small doses. In large concentrations, ammonia can be quite hazardous and, accordingly, ventilation and other safety precautions must be undertaken when working near ammonia. At normal temperatures and pressures, ammonia is a colorless gas made up of one part nitrogen to three parts hydrogen. Ammonia is lighter than air and has a sharp, pungent odor that serves as a warning of its presence. Although ammonia is a toxic gas, it is not a cumulative poison. Accordingly, removal from the source serves as the best protection. Ammonia is highly soluble in water and forms a solution known as ammonium hydroxide (NH
4
OH) or aqua ammonia which is commonly used as a household cleanser.
One industrial application that has historically made liberal use of ammonia is commercial and industrial refrigeration systems. For such a refrigeration system, anhydrous ammonia is typically used. Anhydrous ammonia is the liquid form of pure ammonia gas, and is technically water-free. Most refrigeration experts consider industrial grade anhydrous ammonia to be the most economical and efficient heat transfer medium for industrial refrigeration processes.
In an industrial refrigeration system, compressors, piping, and vessels containing anhydrous ammonia are generally prevalent throughout the plant. Such a refrigeration system will generally also feature lubricating oils which are inserted into the compressor to keep the compressor lubricated. Invariably, some of the oil or other lubricant will migrate throughout the system, mixing with the anhydrous ammonia to coat the piping system. Since the oil will serve as an insulator or retardant to heat transfer, a high prevalence of waste oil in a refrigeration system will compromise efficiency of the refrigeration process. In order to prevent deterioration of the refrigeration function, accumulations of waste lubricating oil will need to be purged from the system. Most commercial and industrial refrigeration units will include one or more ports located at a lower level in the piping system and arranged such that lubricating oil will accumulate there to be drained from the pipes for collection and/or discarding.
In the United States, the International Institute of Ammonia Refrigeration (IIAR) is generally recognized as the leading authority on issues related to the operation and maintenance of industrial refrigeration systems utilizing ammonia. The IIAR has set forth various publications detailing proper practices for the operation of ammonia refrigeration systems as well as safety guidelines. Among the most pertinent guides set forth, Bulletin No. R1 (1983) provides a comprehensive analysis of the use of anhydrous ammonia in a refrigeration system. The IIAR has also set forth specific oil draining guidelines which are to be used in removing waste oil from an ammonia refrigeration system. (See the August 1996 IIAR Oil Draining Guidelines.) The guidelines note that draining oil from an ammonia refrigeration system is a potentially dangerous process and should only be performed by properly trained personnel.
In order to remove used lubricating oil from an industrial refrigeration unit, the typical procedure employed is for an employee to use the refrigeration system pressure if it is positive, or otherwise raise the pressure to a positive value above atmospheric pressure. An OSHA-approved ammonia hose should be screwed into the oil drain valve port. Preferably, the drain line should also include a sight flow indicator such as, for example, Model 700 manufactured by Anderson Midwest. Such an indicator will enable the employee performing the oil removal to know when all the oil is removed and liquid ammonia is passing the sight glass. At that point, the employee will quickly close the valve when it is discovered that all the oil has been drained.
A bucket is placed under the oil drain valve port before the valved is opened, and the oil will flow into the bucket for disposal. In the alternative, hand pumps or mechanical pumps may also be used. Even when a pump is used, the waste oil is still typically removed into a bucket or other open container for removal by an employee. Since the waste oil has been in contact with ammonia, invariably the waste material removed will be a mixture of oil with entrained ammonia.
Under the IIAR guidelines, recognition of the inherent safety risks of removal of the oil-ammonia mix requires that an employee proceed with goggles, gloves and face shield before opening the valve port. In addition, the personnel in charge should check the ventilation fan in the area where the oil is being drained and only perform oil removal when appropriate ventilation is available. As the mixture is released, ammonia will be noticed in the ambient air along with the undesirable environmental effects. The maintenance personnel should always be in a position on the up-draft side of the oil drain bucket for this reason. The IIAR guidelines also state that the personnel should remain in position at the oil pot and keep a vigilant watch during the draining process until such time as the valve has been properly repositioned. Of course, for the personnel involved, the foul smell of ammonia will be prevalent. Since many waste removal ports are located within proximity to other industrial systems or personnel stations, oil draining is sometimes not performed as regularly as it should be. Of course, this leads to the inevitable compromising of the refrigeration system efficiency.
What is needed in the art is a means by which the waste oil can be effectively separated from the ammonia and the ammonia neutralized such as to prevent the undesirable side effects associated with draining waste oil from a commercial refrigeration unit that utilizes ammonia.
2. Description of the Related Art
Since ammonia-based refrigeration systems are old in the art, patents related to the composition of such a system are long expired. Many old patents also disclose systems or mechanisms for removing lubricating oil from a refrigeration system. One of the older patents which is also typical of standard commercial refrigeration oil separation can be found in U.S. Pat. No. 1,836,318 by N. H. Gay. In that refrigeration system, the oil separator noted by numeral 26 in
FIG. 1
is typical. Other patents of note include U.S. Pat. Nos. 3,304,697 by Ramsey wherein a centrifugal separator is disclosed for separating the gaseous and non-gaseous components of a fluid stream including a collection pump and dividing means. U.S. Pat. No. 3,304,741 by Weller also discloses an oil separation system for a refrigeration system wherein an oil separator is positioned at a lower level with respect to a refrigeration system, and comprises an oil sump for gravity flow of oil into the compartment. U.S. Pat. No. 3,438,218 by O'Neil features a standard oil separation system wherein separated oil may be returned to the system.
U.S. Pat. No. 5,407,355 by Sarritzu claims a process of recovery of ammonia from a liquid waste stream. The process consists of reacting the stream with pure carbon dioxide or a gaseous mixture rich in carbon dioxide and then reacting the resulting mix with calcium chloride such as to cause calcium carbonate to undergo thermal decomposition. The thermal decomposition step is carried out preferably not lower than 850° C. Accordingly, the system has little utility for use in connection with a commercial refrigeration system.
U.S. Pat. No. 5,001,908 by Mayer discloses an oil separator for a refrigeration system wherein oil is separated from vaporized refrigerant leaving the high pressure discharge side of the compressor. Mayer states that in the preferred embodiment, oil is removed from the incoming refrigerant vapor
Bertrand, Jr. Marvin Ralph
Masterson James A.
Jiang Chen Wen
Waters Robert R.
Waters Law Office
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