Ken Revell, Business Line Manager Sales & Marketing for Atlas Copco’s Compressor Technique Service Division
Few would deny the logic of ensuring the continued performance of production equipment, but recent findings show that not everyone is aware that the quality of spare parts can have a significant effect in terms of costs and efficiency.
In the case of compressor components, it is essential that high quality systems should be maintained and serviced with genuine spare parts to reduce the risk of performance dips, over-usage of energy and reduced lifetime, all of which can have a negative impact on the compressor owner’s capital investment.
Industry survey results indicate that over 30 per cent of compressor owners rely upon third party service providers to maintain their equipment. These compressor engineers may be tempted by the availability of relatively cheaper; non-genuine ‘soft’ common spare components such as air/oil filters, separator elements, line filter cartridges and, importantly, compressor lubricants.
The result is that compressors may be suffering in silence: in the long term, non-genuine spare parts, including lubricants, can be creating unseen damage to machinery, surreptitiously diminishing efficiency or, worse still, affecting process air purity which in turn might result in end-product quality issues. The impact may not be immediate, although the effect on total lifecycle costs can be massive. To illustrate this, a snapshot survey of compressor owners in 2015 revealed that over 40 per cent had suffered compressor breakdowns during the past year, with some instances of production downtime costs in the region of £20,000.
The optimal operation of a conventional screw compressor is dependent upon lubricants to reduce wear and to seal, cool and clean. Non-specific substitutes are likely to cause problems. The wrong specification can result in poor lubrication of the compressor screw element, which may not seal properly, allowing air to ‘slip’ back and be re-compressed. Each compression cycle reheats the air increasing the operational temperature of the compressor thereby reducing its efficiency and pushing up its SER (Specific Energy Requirement) level.
These are a compressor’s first line of defence for its oil circuits and compression elements against external contamination. When correctly matched to a compressor system, they are capable of a >99.9% separation efficiency and able to extract all particles larger than 3micron in size from the incoming air. But non-genuine units, either of competitive design or actual ‘pirate’ parts, may create problems caused by ingress of unfiltered air. These stem either from dimensional differences, whereby incompatibility of the filter element to its housing increases intake of unfiltered air, or the inferior quality of the filter paper. A chain reaction is created affecting the efficiency of the downstream air/oil filter and the air/oil separator, resulting in significant pressure drops.
Cheaper electrical components are equally tempting but not without risk. A rewind operation for a burned out electric motor may be attractive but a subsequent 10 per cent loss in efficiency may prove less so − replacement with an updated, high-efficiency unit can prove a better proposition. In other areas, system control issues are often found to be the consequence of fitting cheaper but unreliable pressure transducers that are responsible for substantial increases in energy consumption.
Overall, the impact on compressor performance from fitting non-genuine OEM components of this type is hard to ignore. A pressure drop of 1 bar from the oil separator will increase energy consumption by 7 per cent. In the case of air filters, for every 25 mbar pressure drop, compressor output is decreased by 2 per cent.
1 - Compressed air industry survey 2015 (Mark Allen Group)
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