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By Grant Laidlaw
GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy ( ACRA ) in Edenvale . He holds a Bachelor of Business Administration and an associate degree in educational administration . He has a National Technical Diploma and completed an apprenticeship with Transnet . He has dual-trades status : refrigeration and electrical . He has been involved with SAIRAC for over two decades and served on the Johannesburg committee as chairman and was also president between 2015 and 2018 . Currently he is the SAIRAC national treasurer .
REFRIGERANT CHANGES AND LUBRICANTS
PART 2
There are many changes as we move into a new natural refrigerant era . You will find that we have almost as many new oils on the market as there are refrigerants . In Part 2 of this topic , we look at oil types and properties .
Recap of question from Part 1 : Gean asks : Grant , with all the changes with regards to refrigerants how does this affect the lubricants in the systems , aside from the older systems , are we even doing mineral oils ?
Hi Gean , continuing from the last issue of RACA Journal ; until the phaseout of CFC , HCFC refrigerants mineral oils were the primary oils used in refrigeration systems . However , mineral oils are not suitable for use with the HFC / HFO refrigerants . The main reason for this incompatibility is the insufficient lubricity ( lubricating ability ) and miscibility ( mixing ability ).
Mineral oils could remain in use with some of the Hydro Carbon refrigerants . Much work has been done to find acceptable lubricants to use with HFC / HFO / HC and natural refrigerants .
WHICH OIL TYPES ARE USED FOR REFRIGERATION SYSTEMS ?
• Poly alkylene glycols ( PAG ) These refrigeration oils have a high viscosity index and thermal stability . However , PAG is hygroscopic , which means it can attract water . PAG is soluble with ammonia .
• Polyol ester compressor oil ( POE ) High-performance Polyol Ester ( POE ) for refrigeration compressors and systems .
Specifically designed for use with ozone-friendly HFC refrigerant fluids ; formulated from synthetic Polyol Esters to provide outstanding lubricity and wear protection , as well as chemical and thermal stability .
Compatible with R23 , R134a , R404a , R407c , R410a , R410b , R417a , R422a , R422d , R427a , R507 , R507a .
• Alkyl Benzene compressor oils ( AB ) Extreme performance synthetic lubricant for refrigeration compressors with and without ammonia refrigerant .
Image supplied
No ice formation at bottom : refrigerant is lighter than oil ( R717 ). This can be clearly seen by indication of the refrigerant causing ice formation on top and the oil at the bottom causing no ice formation .
Wax-free for excellent low-temperature fluidity and evaporator efficiency . Outstanding thermal / oxidative and chemical stability for long oil life , extended drain intervals , less routine maintenance . Compatibility with seals previously used with mineral lubricant for limited risk of oil leakage .
• Polyalkyleneglycol ( PAG ) compressor oils Synthetic Polyalkylene Glycol based ( PAG ) lubricant suitable for specific refrigeration applications .
Polyalkylene Glycol – based . Shear-stable lubricant with outstanding resistance to thermal degradation and the formation of sludge and deposits . Suitable for HC ( hydrocarbon ) or CO₂ refrigerant fluid applications .
Compatible with R290 , R600 , R600a , R134a ( auto-motive compressor applications ) and R1234yf .
• Polyalphaolefin ( PAO ) These refrigeration oils have a good chemical and thermal stability . PAO also has excellent viscosity temperature characteristics . The miscibility with refrigerant is low , which is why the major use of PAO in refrigeration is in applications where miscibility is not a concern . PAO can cause seals to shrink .
• Mineral Oils Naphtenic oils have a low pour point , which make them more suitable at lower temperatures . Naphtenic oil is derived from crude oil and is processed using a separation process removing all contaminants .
www . hvacronline . co . za RACA Journal I March 2022 37