What characteristics would a lubricating oil have if it were to be used for
-air compressors
-internal combustion engines
-refrigeration systems

thanks
pweng2

I/C engines, assuming 4 stroke (4 cycle) require A/W, detergent / dispersant, rust & corrosion inhibitors, oxidation inhibitors, VI (if multiweight), pour point depressants, and sometimes anti-foam typically in general..
Air compressors, depending on the type (recip, screw, centrifugal, vane) may not require all of the above and would benefit from NOT having most of the 4 cycle type additives.
refrigeration compressors (assuming a screw, recip, or scroll type) would also benefit from not having most of the engine type additives.

What are you trying to do?

Hi there,

In addition to what David has stated I would like to add the following:

Do also look for performance values MIL and API specs for Engine oils, DIN 51524 plus.( There is also a DIN spec for Compressor oil, I am not able to recall off hand)

As far as properties are concerned you should seek
1. Demusibility for compressor oils: Many air compressors work in humid conditions and water vapour is trapped and condensation will result in presence of moisture. It is imperative the oil has a good demusibility to tackle this. Many manufacturers use Turbine oils for compressors. Caution however, the moisture will need to be drawn out through a vent.

2. The Pneurop Oxidation for Compressors oils is a must.

As for Refrigeration oils the floc point, cloud point and pour point ( all are related to each other as it indicates Aromatic content) would be good indicators.

Hussam Adeni

I would like to ask Hussam whether for refrigerant compressor oil should have low aromatic content and whether any relatively purer base oil manufactured compresssor oil can perform better for these applications.

quote:

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Originally posted by Hussam Adeni:
Hi there,

In addition to what David has stated I would like to add the following:

Do also look for performance values MIL and API specs for Engine oils, DIN 51524 plus.( There is also a DIN spec for Compressor oil, I am not able to recall off hand)

As far as properties are concerned you should seek
1. Demusibility for compressor oils: Many air compressors work in humid conditions and water vapour is trapped and condensation will result in presence of moisture. It is imperative the oil has a good demusibility to tackle this. Many manufacturers use Turbine oils for compressors. Caution however, the moisture will need to be drawn out through a vent.

2. The Pneurop Oxidation for Compressors oils is a must.

As for Refrigeration oils the floc point, cloud point and pour point ( all are related to each other as it indicates Aromatic content) would be good indicators.

Hussam Adeni

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Dipen,

Paraffinic base oils are preferred for most lubricant applications. However for Transformer oils, Napthenics are the preferred choice.
Technically speaking, synthetic are the best choice for refrigeration oils.

All lubricant base oils are a mixture Paraffinic /napthenic / aromatic contents. Mineral base oils are largely a result of distillation, which is a physical process. The lube oil distillation units adopt purification processes, like vacuum distillation and solvent refining (which removes aromatics & polar compounds) This combination can extract upto 80% of the aromatic hydrocarbons and other undesirable contents. The Lube oil then goes through a process of dewaxing and finally hydro finishing.

Lube oils may then go through a process of polymerization or synthesis which results in a synthetic base oils. In short, a chemical synthesis results in a synthetic base oil while physical process (distillation) is used for manufacture of mineral base oils.

To answer your question, low aromatic content is the best choice for refrigeration oil. As synthetic oils have the lowest or least aromatic content.

Interestingly, the new breed of base oils (the Group II oils) after undergoing hydro cracking and hydro finishing give the synthetic base oils a run for the money. For base oils, on overall performance as a refrigeration oil I would rate (on a 1 to 10 scale) Synthetic as 10, Group 2 as 8 and other Group 1 plus Mineral oils as 5.

Hussam Adeni

quote:

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I would like to ask Hussam whether for refrigerant compressor oil should have low aromatic content and whether any relatively purer base oil manufactured compresssor oil can perform better for these applications.

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Even though you didn't ask me, here is my reply to your question. The situation is more complex than Hussam has indicated. Standard mineral based refrigeration lubricants used with CFC and HCFC refrigerants are mainly based on naphthenic basestocks. Some compressors require white oils (paraffinics) when extra chemical stability is needed. Both of these basestocks are highly refined and treated to remove hetero atoms and waxes. The oil must be very chemically stable and have no impurities that could cause deposits to form inside the refrigeration loop. Sealed tube stability (ASHRAE 97) and floc point are measures for these characteristics. The other main impurity that is tightly controlled is moisture level.

There are synthetics used as well. Alkylbenzenes are used as synthetic hydrocarbons to provide better oil return characteristics with some refrigerants, as well as increased chemical stability.

Ammonia refrigeration systems use naphthenics as well, but the oil is not soluble in the refrigerant. These systems use oil separators to prevent the oil from getting into the refigeration loop. The reactivity of ammonia is a problem with many basestocks unless they are highly refined and treated.

Some of the newer refrigerants to replace the CFCs are highly fluorinated (HFCs) and are not very soluble with hydrocarbons. Polyolester and polyalkyene glycols are commonly used with HFCs. Again, chemical stability is the primary requirement these lubricants must meet.