Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Lubricant testing
Patent
1994-04-13
1996-02-06
Williams, Hezron E.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Lubricant testing
73 6441, 73 6169, G01N 1506, G01N 3326, F01M 902
Patent
active
054888557
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of testing, and in particular to a method of testing to be used in conjunction with the so-called "retrofilling" of mechanical vapour recompression type heat transfer devices.
In recent years there has been increasing concern about the adverse effects of chlorofluorocarbons and hydrofluorocarbons on the content of ozone in the Earth's upper atmosphere and in consequence then is a need to replace the use of the most damaging halocarbons and hydrohalocarbons in refrigeration and air-conditioning systems with the use of more acceptable working fluids, in particular 1,1,1,2-tetrafluoroethane (R134a).
A procedure which has been found to be particularly effective and successful in converting existing recompression type heat transfer devices to use 1,1,1,2-tetrafluoroethane is the retrofill procedure which is described and claimed in EP-A-0 468 729. When the term "retrofill" is used in this application the term is intended to mean the procedure as described and claimed in EP-A-0 468 729.
The synthetic ester lubricating oils which are particularly suited to the retrofill procedure are those which are described in EP-A-0 468 729. These esters are available commercially under the trade name "CASTROL ICEMATIC SW" (Trade Mark), different mixtures of the esters being tailored for particular refrigerant applications, covering a wide range of lubricant viscosities.
In performing the retrofill procedure this usually comprises the steps of isolating the compressor from the remainder of the system, draining the mineral oil to be replaced from the compressor, filling the compressor with a synthetic ester lubricating oil, reconnecting the compressor and then running the system to flush the mineral oil to be replaced back to the compressor. The amount of running which is required will depend on the particular equipment which is to be retrofilled, e.g. the size and complexity of the system. After this running of the system the lubricating oil is tested to check the content of mineral oil whose presence in the system when the working fluid has been replaced by the new hydrofluorocarbon would be likely to cause problems due to the immiscibility of mineral oils in 1,1,1,2-tetrafluoroethane.
The present procedure for testing of samples of the lubricating oil for mineral oil contamination involves sending the sample to a test laboratory where the sample is tested, usually by thin layer chromatography, to determine the mineral oil content of the sample. However, the fact that these tests cannot be performed on the spot by the service engineer so that it is immediately known whether reflushing is required or whether the system is ready for retrofilling with the new hydrohalocarbon is obviously a serious disadvantage. Since the sample may have to be sent some considerable distance and the test procedure itself requires time to be spent by trained personnel, there may be a delay of days before the result is known, and a further visit by the service engineer would therefore be required. There is clearly a need for a simple test procedure which can be performed on the spot by the service engineer who is performing the retrofilling of the refrigeration system which does not require of the service engineer significant chemical skill or knowledge, and so that he/she can very quickly determine whether the system needs to be reflushed before putting in the replacement hydrohalocarbon.
According to the present invention there is provided a method of testing for contaminating mineral oil in a sample of synthetic ester lubricating oil from mechanical vapour recompression type heat transfer equipment which is to be retrofilled with hydrohalocarbon working fluid, which method comprises: contaminated with mineral oil with a predetermined quantity of a polar liquid or a mixture of polar liquids, the ester lubricating oil being itself completely miscible with the polar liquid(s) and the resulting mixture having the physical property of manifesting a discontinuous change in optical appearance between turbidity when sa
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Carter Brian H.
Rowntree Richard S.
Swallow Andrew P.
Castrol Limited
Wiggins J. David
Williams Hezron E.
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