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ammonia refrigeration system Danfoss

Increasing refrigeration efficiency with right lubricant

How does the right lubricant increase refrigeration efficiency and add to your sustainability goals?

Even though the lubricant plays the main role in the seamless operation of the compressor, it can be noted that it operates only within the compressor and does not enter any other segment in the refrigeration cycle. If, by chance, the lubricant enters the condenser, the expansion device or the evaporator the overall efficiency of the refrigeration process deteriorates.

However, in the case of large scale refrigeration where compressors are at work non-stop, it becomes a challenge to make sure that they are working smoothly and food products are preserved consistently at the required temperature. Apart from seamless power supply, Lubricants play a critical role in keeping the compressors running and delivering optimum refrigeration.  

Refrigeration Cycle Diagram
When oil in the system becomes a challenge

Even though the lubricant plays the main role in the seamless operation of the compressor, it can be noted that it operates only within the compressor and does not enter any other segment in the refrigeration cycle. If, by chance, the lubricant enters the condenser, the expansion device or the evaporator the overall efficiency of the refrigeration process deteriorates.

Studies indicate that 1% of oil trapped in the refrigeration cycle reduces the efficiency of the refrigeration process by more than 10%.

Oil separators are placed in the refrigeration cycle to eliminate this problem, but generally, oil separators are only capable of removing oil particles in the droplet form. The greater challenge is that oil gets evaporated in the aerosol form and this cannot be removed by the oil separator. If this oil (in the aerosol form) enters the refrigeration system, it reduces the efficiency of the entire refrigeration cycle.

Klüber Lubrication swabs the oil issue

Klüber Lubrication with its extensive research capabilities has found an effective solution to this
longstanding problem. Klüber Summit RHT 68 is a specialty lubricant. This refrigeration
compressor oil with its highly refined mineral oil and ammonia composition has a very narrow
molecular distribution. The narrow molecular structure of Klüber Summit RHT 68 ensures that the short/light molecules do not evaporate fast and the long/heavy molecules in the structure do not form sludge. Traditional refrigeration compressor oils, in comparison, have short and heavy molecules in them which cause evaporation and sludge formation.

Molecular distribution of Klüber Summit RHT 68 compared with that of a commonly available product sample.
The lower volatility of Summit RHT 68

Using well-accepted test standards like NOACK Volatility (DIN 51581) it has been recorded that Klüber-Summit RHT 68 has a lower evaporation rate – resulting in a 60% reduction in oil makeup rates. This is a distinct advantage vs. naphthenic oils. 

The lower volatility of Klüber Summit RHT 68 influences the amount of oil vapour carryover with the ammonia gas past the separator. This oil normally does not return to the compressor. Since the oil is heavier than ammonia, these oil vapours are later condensed and collected in the oil traps that have to be serviced (drained) on a regular basis. In most cases, the condition of the collected oil warrants proper disposal; however, Summit RHT 68 from these traps can be re-cycled based on laboratory analysis.

Inert to impurities and reduces operational costs

Conventional refrigeration compressor oils develop a high concentration of impurities like aromatics, sulfur, waxes and unsaturated compounds that reduce extended oil drain capability. These substances also form sludge which can damage machine components and drastically reduce refrigeration efficiency. 

 

Klüber Summit RHT 68 is a hydro-treated oil which is highly inert. It literally generates no impurities and thus helps prevent mechanical component damage. The high-potential lubricant also reduces the number of oil filter replacements. All of this help save time, labour and cost significantly. 

Extends re-lubrication intervals up to three times The highly efficient Klüber Summit RHT 68 can extend the re-lubrication intervals to 10,000-15,000 hrs, while conventional refrigeration oils need to be changed after 3,000 – 5,000 hrs of operation.

Stay-in-grade viscosity and superior thermal stability

Traditional naphthenic refrigeration compressor oils have a higher evaporation rate which leads to higher top-up on a regular basis. Besides, with the reduction of shorter/lighter molecules in the overall composition, the system oil viscosity begins to increase resulting in higher temperatures, deposit formation, foaming and a definite decrease in system heat transfer efficiency. For naphthenic oils, the viscosity increase during operation would be along the lines of 109 mm2/s, from the prescribed viscosity of 68mm2/s. 

 

However, Summit RHT 68 has stay-in-grade viscosity control and superior chemicals that ensure thermal stability with no drop in system efficiency.

Popular across the world

Summit RHT 68 is an all-rounder among refrigeration lubricants. It excellent performance in all conditions has made Klüber Summit RHT 68 the favoured refrigeration compressor oil choice for food processing industries around the world. Furthermore, Klüber Summit RHT 68 is approved by OEMs and packagers like GEA Grasso, Stal, Maneurop, MAYEKAWA Axima, Clauger, GEA Refrigeration and Johnson Controls.

Benefits of Summit RHT 68 at a glance

Problems associated with general refrigeration compressor oils

Solution by Summit RHT 68

Compressor oil entering condenser, expansion valve or evaporator and reducing the efficiency of the refrigeration cycle.

The absence of shorter/ lighter molecules ensure lesser evaporation and thereby increases the operating efficiency of the refrigeration cycle.

Sludge formation

The absence of longer/heavy molecules and other impurities lead to cleaner operation. Plus, Summit RHT 68 can be reused.

Increase in oil viscosity leading to wear and lower efficiency

Summit RHT 68 has stayed in grade properties which ensure that base oil viscosity remains at 68 mm2/s.

Lesser operating life and frequent top-ups

With its superior formulation, re-lubrication intervals are typically 10,000 -15,000 hrs with 60% reduction in oil mark-ups.

Higher spare parts cost

Impurities and sludge are easily removed and better lubrication properties ensure a longer life for components.

Testimonies of satisfaction from users of
Summit RHT 68
Our Mycom screw compressors are running continuously. We measured the rise in discharge pressure and a rise in oil temperature while using Klüber Summit RHT 68. The oil has maintained stable and sensible parameters by maintaining its viscosity. We are fully satisfied with Klüber Summit RHT 68 – this innovative and exceptional refrigeration lubricant from Klüber.” Dairy plant in India
In the lubrication of our Howden compressors with ammonia-based Klüber Summit RHT 68, we confirm energy savings of 3.8%, lubricant consumption reduction of 41.56%, and savings in filter consumption by 7.04%”Tomato Pulp manufacturer, Spain, S.A
On-site we had complications with compressors from Sabore, J&E Hall, York, Frick, Grasso and Mycom. I can confirm that since changing all our compressors to Klüber Summit RHT 68 and Klüber Summit RAB refrigeration compressor oils we have experienced no running problems at all.”Confectionary manufacturer, Great Britain
We have piston compressors from Linde and screw compressors from Stal-Astra on which we are using Klüber Summit RHT 68 for the last 2 years. We confirm that we are very pleased with the performance. The efficiency of the system has improved; output has increased, it has a longer life and requires less lubrication. With Klüber Summit RHT 68 we have cost savings from lowered oil consumption and maintenance costs to lower energy consumption”Beverage Manufacturer, Austria
After switching to Klüber Summit RHT 68 the following results were obtained – noticeably less oil evaporation into the refrigeration system, longer oil makeup period, the oil behaves optimally in the evaporator, it maintains its fluidity at low evaporation temperature, better system efficiency providing electrical energy savings and less foaming. The lubricant Klüber Summit RHT 68 met our required expectations; therefore we recommend this product for lubricating MYCOM rotary screw compressors.”Poultry products manufacture, Ecuador

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