COOLING SYSTEMS AND LUBRICANTS
Our company En-Ser Contracting&Trade Co., has been mainly involved in the field of Cooling Compressors and Cold Room lubricants for the last twenty five years.
Particularly, after 1990’s, parallel to the increase of research and development on cooling compressors, more efficient systems have been developed resulting in less operational costs but also needing new types of cooling lubricants.
In our country, besides usage of new age amonium gas cooling compressors, with screw or piston systems, usage of new types of freon gas compressors are also common. With less frequency, carbondioxide compressors can also be seen in the industry.
Ammonia compressors are mostly seen in large food-processing and cold preservation sectors, together with shock freezing industries especially in fastly perishable groups as fruits, vegetables and also in milk, meat and drugs preservation fields.
As to the GWP(Global Warming Potential) and ODP(Ozone Depletion Potential), freon gases as HFC( Hydro Flora Carbon), CFC (Cloro Flora Carbon) have more negative effect on environment than ammonia gas, which has almost zero effect on environment and therefore is mostly preferred in line with Kyoto Protocol.
On the other hand, ammonia gas compressors are proposed for mostly large systems, since these systems are not appropriate for mobile installations.
In freon gas compressors, the least GWP and ODP depletion can be maintained only by usage of R600(Isobutanes), which are mostly utilized in home and market freezers and shock coolers.
Other freon gases as R134a is mostly used in vehicle air conditioners, R 290 in heat pumps, R404a, R406a or R410 are used in bigger air conditioners and coolers. This last group of gases are usually combined HCFC (Hydro Cloro Floro Carbon) gases formed to reduce climate effects.
The following lubricants are commonly used in accordance with the operational requirements and in line with compressor types:
• Naphthenic Based Lubricants
Naphthenic base lubricants, which are mineral oils, are produced with vacuum distillation method inrefineries, which are later refined with solvent in order to eliminateheavy components as nitrogen, sulphur and asphaltic residues, and lastly by applying 800 atmosphere pressure to detach wax remnants almost to %85 from the lubricant.
Naphthenic oil series are mostly used in older technology ammonia cooling compressors(as before 1980’s) and also with R-22, R-12 Freon gas compressors.
In these com pressors, usually the maximum operational cooling temperaturs do not exceed -300C. These oils are introduced to users after enriching and strengthening with adequate additives.
• HT (Hydrogen Technology Applied) Semi-Synthetic Lubricants
These types of oils are double treated with 4000C and under 3000 atmosphere pressure, in order to eliminate nitrogen, sulphur and other aromatic components from the base mineral oil to attain %99,9 purified lubricant.
At the last stage, they are strengthened by synthetic additives as pour point depressants, viscosity stabilizers and anti- corrosives to give best performance under harsh operational conditions.
In these lubricants, about %97 of the lubricant consists of the HT purified base lubricant and about %3-5 percent consists of the above mentioned synthetic additives, therefore they are mostly named as semi-synthetic lubricants. These lubricants can be used up to -400C to -420C degrees in compressor operations.
• Naphthenic Based Semi Synthetic Lubricants
Base naphthenic oils produced with solvent application are detached from wax ingredients are later mixed with full synthetic PAO (Polialphaolephin) in
order to produce a resistant structure to harsh operational conditions, which are also strengthened with synthetic additives.
Such oils are usually used up to -390C operational degrees in ammonia cooling.
• PAB Based Lubricants
Such oils are fully synthetic oils produced with fully synthetic PAB(Polialklybenzene), which can resist to very harsh conditions and can be used up to -450C operational conditions
• PAG Based Lubricants
Such oils are produced with fully synthetic PAG (Polialkylglycol), to resist harder operational conditions and can be used in compressors with mostly high compression pressures and high exhaust temperatures. They can also face higher cooling temperatures.
– In most ammonia compressors, the preferred lubricants are at 68 cst. viscosity.
The lubricants used in freon compressors vary in accordance with compressor type and compressor producer’s advise. These lubricants are generally POE (Poliolester based) fully synthetic lubricants and should also be selected in line with the freon gas type used in the compressor.
For instance, freon compressors with R 134a, R404a or R410a that operate up to -450C operational temperatures, the appropriate viscosity of lubricant should be around 32 cst.
With similar gases, but -420C operational temperatures, the required viscosity will be 46 cst. and with -390C temperature, the viscosity of lubricant would be close to 68 cst.
In cooling systems, cold room temperatures may vary from +40C up to -550C. range. In consistence with the operational degrees and conditions, the types of lubricants and greases should also be selected correctly.
The equipment’s or processing devices employed in the cooling tunnels and rooms should use synthetic and mostly food certified lubricants with varying pour points from -300C up to -700C degrees. In such environment, sizely cooling fans,
IQF (Quick Freezing Equipment’s) and shock tunnel equipment’s, as rolling bands etc. need special high pour point lubricants with generally food grade characteristics, namely NSF- H1 and NSF- H3 coded certificates.
In the cold logistics area, generally employed air conditioners and coolers use R404a, R408a, R410 a freon gases. In some cool chains, cold boxes of various sizes are also used together with freon gas compressors.
In such systems the break down of the cold chain should not be allowed, especially for fruits, vegetables, meat and milk groups, otherwise, big quality and commercial losses may be incurred due to bacteriological destructions and aromatic losses in these products.
Currently, most of the cooling lubricants are imported to Turkey. Even though, in the last years, few companies which follow current technologies and appropriate equipment’s, started to produce ammonia compressor oils.
Lubricants production requires a very sensitive application of production methods, appropriate selection of the additives and continuous follow up with laboratory analysis of the product specifications along
with customer feed backs.
Kudret Tan – Endüstri Yüksek Mühendisi – MSc. Industrial Engineer –En-Ser Taahhüt ve Ticaret – En-Ser Contracting and Trade Co.
