Refrigeration – Processes – Lubricant handling
Patent
1995-07-13
1997-06-17
Sollecito, John M.
Refrigeration
Processes
Lubricant handling
62468, 62475, F25B 4302
Patent
active
056386907
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the conversion of a refrigerating machine or a heat pump from operation with a first type of refrigerant to operation with a second type of refrigerant and relates to a method of removing the lubricating oil that is contained by the system and used together with the first type of refrigerant, and replacing this lubricating oil with another lubricating oil that is compatible with the second type of refrigerant. The invention also relates to an arrangement for use when carrying out the method.
Because the refrigerant typically used in refrigerating machines and heat pumps is comprised of CFC-compounds (fully halogenated chlorofluoro-substituted hydrocarbons) which have a deleterious effect on the atmospheric ozone layer, drastic measures have been taken to eliminate the use of such compounds. Since the replacement HFC-compounds (hydrofluoro carbons) are chlorine-free, they require the use of lubricants other than the mineral oils or alkylbenzene oils used today. The lubricating oils are primarily used to lubricate and to seal the compressors of the refrigerating systems.
The oils mainly used together with chlorine-free refrigerants are polyester oils. Since residues of mineral oil in the refigerating system can result in a number of problems, a limit of 1% has been placed on the amount of mineral oil that is allowed to remain in the system. However, since oil is dispersed throughout the whole of the system, only some of this oil can be drained from the system through the compressor drainage hole; it will be observed that not all compressors are equipped with a drainage hole. When circumstances are favourable, about 80-90% of the oil can be removed from the system without difficulty. At least 3-4 oil changes are normally required to reach a residual mineral oil content of 1%. These oil changes must be made while running the system for a given length of time between each change, so that mineral oil is able to mix with the ester oil. The cost entailed by such a process is very high, since it requires several visits by a service technician. Oil consumption also becomes relatively high. The method also presumes that the compressor is functional. If a compressor malfunctions or breaks down, it is not possible to terminate the system cleansing or purging process until a new compressor has been fitted, whereby this new compressor will also be "contaminated" with the mineral oil. The compressors are to a very large part completely hermetic and are soldered in the circuit, which means that solder must be removed in order to allow oil to be drained-off.
Some manufacturers of refrigerating machines and heat pumps recommend replacement of the compressor when converting from CFC to HFC. This requires, however, dismantling the system and buying a new compressor.
The main object of the present invention is to provide a method and an arrangement which will enable existing refrigerating machines and heat pumps to be cleansed or purged of oil in a simple and effective manner, without needing to dismantle the refrigerating machine or heat pump. Another object is to enable the refrigerating machine or the heat pump to be cleansed of oil quickly and at low cost.
The invention is based on the realization that because the refrigerant is able to dissolve oil and because the density of the refrigerant is higher than the density of the oil, whereby the refrigerant is able to lift and transport the oil in the system, the refrigerant can also be used to cleanse the system of oil.
When tapping refrigerant from refrigerant carrying systems, for instance when servicing the systems, it has earlier been normal practice to separate the oil from the mixture of refrigerant and oil drained from the system. In this case, however, the oil removed is restricted to the amount of oil that accompanies the mixture drained from the system. Oil which is located beneath the tapping level will therefore be left in the system.
When practicing the present invention, essentially all oil is removed, by flushing the syste
REFERENCES:
patent: 4441330 (1984-04-01), Lower et al.
patent: 4476688 (1984-10-01), Goddard
patent: 4934490 (1990-06-01), Sapp
AKA Industriprodukter Kyla AB
Sollecito John M.
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