Cooling systems and refrigeration oils

COOLING SYSTEMS AND COOLING OILS

As En-Ser Contracting and Trade, we have been operating for approximately 25 years, primarily in the field of cooling compressor oils and cold storage room oils.

Particularly from the 1990s onwards, both in the USA and Europe, cooling compressors underwent continuous R&D development and new-generation compressors with higher efficiency operating at lower running costs were manufactured. In parallel with this, new types of oils were developed to meet these requirements.

In our country, in addition to ammonia gas-based screw and piston compressors, new-generation freon compressors using freon gases are also used. Although less common, new-type compressors using carbon dioxide gas are also in use.

Ammonia-cooled compressors are used primarily in large food processing and storage facilities, shock-cooling industrial operations, rapidly perishable fruit and vegetable processing and storage facilities, and in what we call the sensitive category—dairy and meat products as well as the pharmaceutical industry.

Ammonia gases, compared to HFC (Hydrofluorocarbons) and CFC (Chlorofluorocarbons), have near-zero impact in terms of Global Warming Potential (GWP) and Ozone Depletion Potential (ODP) and are recommended within the framework of the Kyoto Protocol rules.

However, ammonia gas compressors are not suitable for portable systems and are preferred mainly in large systems. In freon compressors, the gas that can provide the lowest GWP and ODP values is HC-based R600 (Isobutane), which is used in refrigerators and freezers.

Other freon gases include R134a, particularly preferred in car air conditioning systems, R-290 and R-1270 used in heat pumps, and mixed HCFC (Hydrochlorofluorocarbon) gas compounds such as R404a, R406a and R410a used in air conditioning systems. In ammonia compressors, the following oils are used depending on the type of compressor and operational requirements:

• Naphthenic Base Oils

These are mineral oils, obtained in refineries through vacuum distillation, subsequently refined from asphalt products in solvent and undesirable heavy compounds such as sulfur and nitrogen compounds, and finally purified of waxy compounds at a rate of 85% under 800 atmospheres of pressure with the aid of solvent.

These oils are used mainly in ammonia-cooled cooling compressors using older technology (1980 and earlier) and in screw and piston compressors using R-22 freon gas.

The lowest temperatures reached by these compressors in evaporators generally do not exceed -30°C. These oils are supplied to users by the manufacturer with the addition of necessary protective and reinforcing additives.

• HT (Hydrogen Technology) Refined Oils

These products are base oils refined twice consecutively in refineries under high pressure (at approximately 3,000 atmospheres) and at approximately 400°C temperature, resulting in 99.9% purity and purified of sulfur, nitrogen and all other aromatic compounds. In the final stage, the manufacturer adds protective additives and synthetic additives that reinforce molecular structures and control fluidity.

These oils are called semi-synthetic as they consist of 97% HT base oil and 3% synthetic additives. Operating temperatures reach -40°C.

• Naphthenic Base Semi-Synthetic Oils

Another type used in ammonia compressors is created by adding PAO (Polyalphaolefin), which has characteristics closest to mineral oils, to naphthenic oil purified of waxy compounds through solvent refining. These are also called semi-synthetic naphthenic oils. Operating temperatures for these products generally reach -39°C.

• PAB Base Oils

These are fully synthetic base oils called Polyalkylbenzene. They are used primarily at very high cooling temperatures of -45°C and above.

• PAG Base Oils

These are Polyalkylglycol base oils, products manufactured for more demanding conditions. They are particularly used in compressors with high compression pressures and cooling temperatures.

- In ammonia compressors, oils with 68 cst viscosity at 40°C are most commonly preferred.
In freon gas compressors, oils of different viscosities are used depending on the gas to be used and the oil viscosity recommended by the compressor manufacturer. These oils are generally all fully synthetic Polyolester (POE) base oils and must be used in the viscosities recommended according to the gas used by the compressor.

For example; in freon compressors using r134a, r404a and r410a gas, if maximum operation cooling temperature is -45°C, more fluid 32 viscosity oils are recommended; in compressors with maximum operation temperature of -42°C, 46 viscosity oils; and in systems with operational temperature up to -39°C, 68 cst viscosity oils are recommended.

In the cooling sector, cold storage and shock-cooling rooms generally have various storage environments ranging from +4°C to -55°C. Equipment used in cold rooms must use oils and greases suitable to these conditions, and most of these products must be fully synthetic and even food-certified products.

Generally, special oils and greases with pour points ranging from -30°C to -70°C are recommended for use. Large fans and shock-cooling systems in these environments, as well as IQF equipment (Quick Freezing Systems), generally use food-certified special greases and oils.

In systems with possible food contact, food-approved products must be used, and these certificates must carry the NSF H1 or NSF H3 codes.

In the cold logistics sector, an important link in the cooling chain, cooling systems generally using freon gas compressors are preferred, and in our country such equipment prefer freon gases such as r404a, r408a, r410a.

In some cold transport chains, both cold transport boxes (specially insulated and ice-containing) and freon-cooled air conditioning systems are used.

In these systems too, maintaining the chain is important at every stage, otherwise bacteriological deterioration occurs in fruits and vegetables and sensitive meat-dairy products, resulting in losses in product aroma and essential liquids. A significant portion of oils currently used in our country is imported from abroad.

However, in the last three years, a small number of oil manufacturers following developing technology have begun producing ammonia compressor oils in Turkey.

Oil production is an advanced technology field requiring compliance with certain standards, conducting intermediate and final inspections in analysis laboratories, and carefully using correct reinforcing and protective additives in correct proportions.

In this field, feedback from oil consumers and monitoring of analysis results contribute greatly to product development work.

Kudret Tan - Industrial Engineer - MSc. Industrial Engineer - En-Ser Contracting and Trade - En-Ser Contracting and Trade Co.