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What kind of oil should I use for my air compressor?

Compressor

Just like vehicles need a specific grade and type of oil to achieve optimum performance, so does equipment such as air compressors. Employing the correct oil for your compressor can benefit your equipment in several ways, including decreasing how much friction is created between motor components, reducing energy consumption and extending the lifespan of the compressor.

In this blog, we will examine why air compressor oil is unique and what type of liquid lubricant is the best product for an application.

Defining air compressor oil

A specialised lubricant, air compressor oil is used to mitigate premature wear and damage in air compressors. There are two different types of compressor oil, synthetic and natural. However, compressor oils offered also vary in terms of their viscosity and the additive packages they contain. This type of oil is significantly different from motor oil as it has less carbon and sulphur and contains no detergent.

Properties of compressor oil

While compressor oils lubricate the innerworkings of compressors, they also deliver many other benefits to equipment and its use. These include the following:

Heat absorption

Compressor oil absorbs heat that is produced from compressed air, helping to keep the compressor at much cooler operating temperatures.

Oxidation resistance

Compressor oil typically contains additives that can slow acid formation and the oxidation process.

Extended lifespan

Additive packages included in air compressor oil during formulation also increase the specialised lubricant’s active service life, help it become compatible with a broad range of conditions and protect components when they are on standby.

Viscosity at cold temperatures

While some oils will fail to perform once the temperature falls, air compressor oils maintain their viscosity even in cold conditions.

Demulsification

Compressor oils also contain additives engineered to enhance water separability, which can protect a working compressor from oil and water emulsions.

Anti-foaming capability

When large air bubbles rise to the surface of an oil, a foam develops. Unfortunately, this increases oxidation as it exposes more of the surface of the oil to oxygen. If no anti-foaming additives are included, oil separators are saturated by this foam, decreasing an air compressor’s lifespan. The reason for this is because oil separators that become saturated cause a drop in pressure, which leads to increased energy consumption.

Selecting the right oil type for a compressor

As we touched upon earlier, the two most basic types of compressor oil are synthetic and standard. Users will find that each one of these options has distinctive attributes.

Standard air compressor oils are made with a mineral base oil. This type of oil is less expensive than a synthetic oil and is recommended for use by homeowners or operations where compressors do not have to work constantly. As a rule, it can also be a suitable choice in compressors that must only handle light to medium duty work.

Synthetic compressor oils are manufactured with a synthetic base. Synthetic oil undergoes considerable processing, making it a more refined product than standard air compressor oil. If you run a professional operation that uses a compressor at a minimum of three times each week, a synthetic air compressor oil is the best option to select. Synthetic oil will enable your compressor to operate more smoothly with reduced noise. Additionally, it will protect the compressor from overheating. The reason for this benefit is that synthetic oils have a much wider temperature range overall.

Although rotary and reciprocating screw models can operate with a wide selection of oil products, original equipment manufacturers (OEMs) often recommend that users employ synthetic oils as these types of oils have no sulphur or harmful additives that can result in unwanted deposits building up on compressor valves.

What are the main advantages of using a synthetic oil for a rotary screw air compressor?

Synthetic oil has multiple benefits if you are using a rotary screw air compressor. These are as follows:

Extended lifespan – Using a synthetic oil can lengthen a rotary screw air compressor’s active service life by as much as 8,000 hours.

Cooler temperatures – Synthetic oils remain cooler while compressors operate and produce lower temperature air discharge.

Fewer deposits – A synthetic oil can also greatly reduce deposits like sludge and varnish formation that can cause premature wear and harm an air compressor’s performance.

Lower oil consumption – As a rule, synthetic oils are consumed at a far slower rate, resulting in longer oil change intervals.

How can synthetic oil help reciprocating air compressor performance?

Reciprocating air compressors can also access many benefits from the use of synthetic oil, such as:

Extended component lifetime: Synthetic oils can help stop piston rings and packings from premature wearing.

Safer operation – Synthetic oils possess much higher flashpoints and auto-ignition temperatures, making them safer for operators.
Low carbon accumulation – A synthetic oil can reduce how much carbon builds up on the valves and can substantially decrease feed rates.

Always select the compressor oil recommended by the manufacturer of your air compressor.

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Everything you need to know about refrigeration oils

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While refrigerants are essential for a refrigeration system’s cooling properties, a dedicated refrigeration oil is vital for correct functionality of the compressor. Lubrication solutions for refrigeration compressors cut back friction, mitigate wear and work as a seal between both the low- and high-pressure sides.

Although the core function of a refrigeration oil is to lubricate, it must also be capable of withstanding extreme temperature differences and be compatible with any refrigerant at any given time. In this in-depth blog, we will take a closer look at refrigeration systems, refrigerants and the type of oils used, as well as the important properties they must possess to perform their role. Read on to learn more.

How do refrigeration systems operate?

A typical refrigeration cycle is performed by first circulating, then evaporating and condensing a refrigerant within a closed system. Refrigerant evaporation happens at low temperature and pressure, while the condensation process takes place at high temperature and under high pressure. As a result, heat transfer is possible from low temperature areas to areas of high temperature.

First, hot compressed vapour will enter the condenser. Here, it is cooled and then condensed into a liquid form, causing heat to generate. The refrigerant enters the refrigeration system’s compressor during the vapour phase and is then compressed to a much higher pressure. This results in a far higher temperature. Once cold, the mixture then enters the evaporator, and the liquid part of the refrigerant mixture is then evaporated.

The condensed liquid refrigerant now flows through the system via an expansion valve and the pressure is effectively reduced. This reduction in pressure results in the evaporation of part of the liquid refrigerant. As a result, the temperature of the liquid-vapor refrigerant mixture is lowered.

What types of refrigerants are utilised in refrigeration systems?

Chloro-Fluoro-Carbons (CFCs) are the first group of refrigerants used and are considered the most harmful to the environment. Examples include R11, R12 and R13, among many others. Hydro-Chloro-Fluoro-Carbons (HCFCs) are another type of refrigerant that are safer, still slightly harmful to our environment. Examples of HCFCs include R21 and R123. Hydro-Fluoro-Carbons (HFCs) are not harmful to the atmosphere refrigerants or the ozone layer. Finally, Ammonia is sometimes used and, while it is eco-friendly, it is exceptionally toxic to people.

Requirements of refrigeration oils

To be effective in refrigeration systems, oils used must have specific qualities that allow them to help equipment function effectively. The following is a list of the key requirements of a refrigerant oil.

Thermal stability

Dedicated refrigeration oils must be able to function properly over a broad temperature range. Process end compression temperatures within refrigeration compressors can hit top temperatures of 180ºC. As a result, refrigeration oil must have thermal stability. If an oil used contains volatile oil fractions, its lighter ends will enter the compressor system in vapour form, where they will condense and decrease the heat transfer efficiency, while simultaneously increasing the viscosity of the oil.

Chemical stability

To avoid a chemical reaction with the dedicated refrigerant, the refrigeration oil used must be chemically stable.

Refrigerant to oil solubility

Oil and refrigerant mixtures may be partly insoluble or soluble. Total solubility helps lubrication, although it can lead to substantial viscosity drops within the compressor that can cause increased friction and undue wear. To work effectively, the oil-refrigerant solution must have a viscosity that is adequately high to provide efficient lubrication and sealing inside of the compressors it serves.

Vapour pressure

When liquids boil, the extra heat is employed to increase the molecule’s kinetic energy, until they cannot remain in a liquid phase and start to form into a vapour. This occurs at a specific pressure, but if this pressure is increased, the boiling point will also increase.

The relationship between boiling temperature and pressure for saturated conditions is dictated by the “vapour pressure diagram”.

What types of oil types are utilised in refrigeration systems?

There are four different kind of refrigeration oils that are typically used in refrigeration systems. These are as follows:

Alkylbenzenes (ABs) are refrigeration oils with good chemical and thermal stability. They are highly miscible with refrigerants and are entirely soluble with both PAO and mineral oils. This makes it possible to create mixtures to improve lubricant properties.

Polyalphaolefin (PAO) also have a good thermal and chemical stability. PAO also offers outstanding viscosity temperature attributes. It has low miscibility with refrigerants and, as a result, it is mainly used when miscibility is not an issue. PAO can lead to seals shrinking, but this issue is solved when it is mixed with AB refrigeration oil.

Polyol ester or POE refrigeration oil is perhaps the most common synthetic lubricant that is used with HFC type refrigerants.

Finally, Polyalkyleneglycols (PAG) are refrigeration oils with thermal stability and high viscosity index. Hygroscopic, they attract water and are soluble with ammonia.