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Divide and conquer

Fitting efficient oil separators on a refrigeration system can tackle a number of energy-sapping issues, says Craig Hughes

As well as reduced efficiency and increased running costs, excess oil circulating in a system can create a lesser-known issue – it will also coat the internal drier cores in the system with a film of oil.

This stops the drier cores doing the job they are designed for, which is removing moisture and acid from the system.

Dirty oil circulating in the system will cause the same problems as excess oil, but with the added danger of compressor burnout, moisture, acid and dirt in the oil will degrade the lubrication properties of the oil and this can cause serious damage to the compressor – excess oil reduces efficiency, dirty oil kills compressors.

Excess oil in the system is mainly caused by an inefficient oil separator, the separator may be undersized or of a poor design.

If the oil separator cannot remove oil efficiently, the oil will simply pass through the separator and be re-entrained back into the system.

There are many reasons why oil separators will not separate efficiently, but the main problem is with velocity-dependent separators, which rely on a high velocity through the vessel to separate the bulk of the oil from the refrigerant gas.

If the system load is reduced, then velocity will be reduced dramatically, lowering the separation efficiency of the separator.

An efficient oil separator on a system prevents oil in the discharge gas from migrating through the system – this oil builds up a thin film on the internal surfaces of heat exchangers and acts an insulator, reduces cooling capacity and the systems compressors have to work harder to maintain the design temperature, thus increasing energy consumption.

The oil in the discharge gas should be separated and held in the oil reservoir, before being metered back to the compressor crankcase to lubricate the internal components.

No time to waste

Problems affecting the ongoing business of a supermarket require immediate action to keep the store in business and prevent product loss.

Refrigeration service engineers are under pressure to resolve problems quickly. If the problem is oil-related, the cause may not be easily identified.

The quick solution is to add more oil. The real solution is to stop oil carryover at source and keep the oil in the compressor sump, where it belongs.

An efficient oil separator will eliminate oil carryover.

Retrofitting Temprite into problematic systems has produced significant improvements.

Massive amounts of contaminated oil have been removed. The oil removed is restored to near-virgin state and may even be re-used.

Design efficiency is restored. Compressor lifecycle is extended.

Temprite introduced the first coalescing oil separator to the market in 1998. These coalescing oil separators are not velocity-dependent and can therefore separate 98.5 per cent of the oil from the refrigerant gas down to 20 per cent of the system design capacity.

Temprite coalescing oil separators provide maximum protection and eliminate oil-related problems.

Coalescing separators are capable, with proper design, of removing 98.5 per cent of the oil component of mass flow. This prevents insulation in the evaporator and a reduction in efficiency.

POE oils and new refrigerants have a powerful solvent effect, ensuring that contaminants in pipe work and components are flushed through the system, degrading oil in the compressor sump.

Removal of solid contaminants down to 0.3 microns keeps the oil clean. Non velocity-dependent separation achieves maximum efficiency across a wide range of operating conditions. 


On a site at a large food processing plant, an LT system with four compressors running constantly only achieved -18 deg C of the design temperature of -21 deg C. After retrofitting a Temprite Coalescing Separator, the engineer removed 120 litres of dirty oil from the system. The result was that the compressor run times reduced from 18 to 13 hours a day, achieving a temperature of -21 deg C.

During a major retrofit programme for a supermarket chain, the main contractor stopped cutting out and renewing the low-level piping and valves because they were so clean when a Temprite Coalescing Separator was installed.

Retrofitting Temprite achieves total system clean-up and is a good preparation for refrigerant change, as required in R22 removal.

Craig Hughes is managing director of Temprite

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