LUBRICATION
Working with
Clean Compressed Air
Two key factors play a major role in compressed air generation: high availability of clean
compressed air and generation at reasonable cost. Newly-developed synthetic compressor oils
have proven their worth in practice. Long oil lifetime, high efficiency and a very low oil content
in the compressed air combine to reduce operating costs considerably.
creased performance compared to conven- compressor availability, reduced total cost
Ro b ert Co r n a tional compressor oils. for oil, oil filters and oil separators as well
Sales Manager Compressors as reduced disposal costs. Furthermore, the
Klüber Lubrication Benefits of Synthetic right compressor oil increases compressor
Deutschland KG Compressor Oils performance with the same power input ow-
robert.corna@klueber.com Special oxidation-resistant compressor oils ing to its high lubricity base oil combined
Germany
ensure reduced maintenance costs, higher with the optimum additive package. During
C
ompressed air is the fourth ener-
gy utility after electricity, gas and
water. Few production lines in the
world would run without it. The majority
of compressed air is provided by oil-inject-
ed screw compressors and the compressor
oils play a major role in generating clean
compressed air in an energy-efficient way.
They account for less than one percent of
the cost of compressor operation; however,
the right oil helps save a considerable part
of the total cost. The oil has three key func-
tions: first it ensures that the rotors and ro-
tor bearings in the compressor are lubricat-
ed, second it dissipates the heat of the com-
pression process and third it forms a seal-
ing film at the seal edge between the rotor
and the compressor casing.
For efficient and trouble-free production,
an oil with long service life and good tem-
perature behaviour with low residual con-
tent in the compressed air is required. How-
ever, there are considerable differences be-
tween the performances of different com-
pressor oils. A well-formulated synthetic
product has considerable advantages over
mineral oil-based products and stands out
in particular for optimum oxidation pro-
tection, good adhesion and low residue for-
mation. The newly-developed synthetic oils If and when an oil change is necessary can easily be determined
stand out because of their considerably in- with the Klüber Summit TAN kit.
10 Maintworld 2 • 2012
times longer than with the previously used
compressor oil. Summing the total costs for
oil change, disposal, oil filters, oil separa-
tors and maintenance, the premium prod-
uct turns out to be the most cost-efficient
one. The total cost calculation in the above
example reveals considerable cost savings.
More compressed air can be produced with
the same energy consumption (improved spe-
cific performance).
Special synthetic oils have been devel-
oped especially for the lubrication of heav-
ily-loaded air compressors with projected
oil change intervals of up to 10,000 oper-
ating hours (under normal operating condi-
tions). They are neutral towards most elas-
tomer seals used in air compressors. Special
Oil service life in compressors used by a manufacturer of particle boards could be quadrupled. inhibitors keep compressors clean on the in-
side to avoid cleaning costs and unplanned
the compression process, this product will downtime. Following precise analyses we compressor downtime.
avoid decomposition, oxidation and residue recommended on-line cleaning of the com-
formation of the oil. pressors and changeover to synthetic oil. Af- Easy Compressor Cleaning
A compressor basically “destroys” the ter cleaning, the compressor could be oper- Mineral oil-based compressor oils can cause
oil during operation, with several factors ated up to 15 Kelvin cooler than before. Ad- varnish and carbon build-up, especially in
having an effect on the oil: high pressure, ditionally, the cooler no longer required an oil-injected screw compressors and rotary
continual intake of fresh air, high temper- annual strip and clean, the operating hours vane compressors, which settle in the en-
atures, considerable shearing forces, parti- increased to over 4,000 and maintenance tire oil circuit. In hydraulic systems, mineral
cle intrusion and atmospheric humidity. All costs were decreased considerably while the oils can cause glueing of valves on hot sur-
these factors cause ageing of the oil, which oil price was comparable. faces, resulting in high energy consumption,
shows mostly as oxidation. At temperatures Some synthetic oils have been devel- clogged oil ducts and filters and high main-
between 90 °C and 100 °C or more and oped especially for compressors in the food- tenance costs and downtime.
under continual oxygen intake, organic ac- processing and pharmaceutical industries Effective ester oil based cleaning concen-
ids produced by oxidation quickly decom- where compressed air can contact the end trates with cleaning additives are available,
pose the oil. The concentration of such ac- product during the production process. With they are used in a 10 % concentration in
ids is expressed by the so-called neutralisa- NSF H1 registration and certification accord- the oil filling 60 hours prior to the next oil
tion number; the lower this value is, the low- ing to ISO 21469, these oils support man- change and run normally. The cleaning con-
er the extent of oxidation. ufacturing plants in their compliance with centrate dissolves residues on the surfaces
Condensate produced by air humidity is demanding hygiene requirements. Synthetic while the compressor is in operation and en-
another factor leading to high maintenance oils show very good resistance to oxidation, sures that they remain dissolved in the oil to
costs as it must be processed prior to dispos- which means that the presence of oxidation be flushed out at the oil change. This meth-
al to the sewage system. Unsuitable oils or residues or lacquer in the compressor is min- od is much more effective than flushing the
low-quality additives lead to emulsification imised. Oil change intervals can be extend- compressor with normal compressor oil. The
of the condensates, making it impossible to ed, e.g. up to 5,000 operating hours in oil- operator can easily determine if and when an
separate oil and water in a normal separator, injected screw-type compressors. Besides re- oil change is necessary with quick test kits
which requires more-expensive condensate duced maintenance and operating costs, this to check the ageing condition of compres-
separators and increases cost. Particularly in enables higher operational reliability. sor oils. The test uses the breakdown acids
the food-processing and pharmaceutical in- Another example is a manufacturer of in the oil to indicate by colour the extent of
dustries, the oil content in the compressed air particle boards. Compressor oil changes oxidation of the used oil.
must be as low as possible and compressor were required after 2,000 operating hours
oils must be registered as NSF H1. and the recommendation was to change to Conclusion
synthetic compressor oil. After 8,000 oper- Practical examples show that changeover to
Convincing in Practical Operation ating hours the used oil analysis in the lab- fully synthetic compressor oils can be made
A leading sausage manufacturer was hav- oratory revealed that additive degradation very easily. Oil service life can be consid-
ing trouble with his NSF H1 compressor in the oil had started, however the oil would erably extended and compressor perform-
oils. Oil service life of less than 1,000 hours not have to be changed for another 2,000 ance increased to save costs and valuable
caused high maintenance costs and frequent hours. Hence, the oil service life was five resources.
Maintworld 2 • 2012 11
