The quoted "basic rules" apply to all industries, areas of application and machine elements. In addition, there are still special requirements which must be taken into account, for example, when selecting gear, hydraulic and compressor oils.
Gears can be lubricated with oils based on mineral oil/white oil, polyglycol or ester. Today, PAO-based gear oils are a bestseller because they are usually well compatible with the residues of previously used mineral oils and also contain very effective EP additives.
In most cases, compliance with DIN 51517 alone is not sufficient to describe the performance of gear oils. Often, additional named approvals from the gear manufacturer or special wear tests, such as an FVA pitting test, are required. A thorough used oil analysis can quickly prove whether the wear protection behavior is really sufficient, even if a good FZG value is proven for the fresh oil.
Hydraulic systems can usually be re-oiled from mineral oil-based hydraulic oils to PAO H-1 oils without any problems. But despite good miscibility, it should be checked whether the additives of the oils are compatible with each other. Otherwise, foam may form or the air release properties of a mixture may become so poor that pump damage due to cavitation is imminent.
If a detergent HLPD or a zinc-containing HLP hydraulic oil was previously used, the re-oiling process should be controlled by laboratory analysis until the calcium or zinc value is below 15 ppm.
Rotary screw compressors often produce the compressed air for food packaging machinery. Oil mist constituents can enter food products with the compressed air. Since mineral oil-based compressor oils often only have a relatively short service life, synthetic H-1-based compressor oils should be given preference in the interest of longer oil change intervals. However, ester oils can become problematic in oil-flooded compressors or where there is a high water content.
Oil analyses not only show how long the oil can remain in use in each case, but also provide information about functioning water separation.
The conversion from conventional greases to H-1 greases is much more difficult than with oils. Bearings or lubrication lines can usually not be cleaned of the previous grease without problems or only with considerable effort.
Extreme care is also required when selecting suitable physiologically harmless lubricating greases. Especially here, advice should be given by an experienced sales engineer of the grease manufacturer. In case of missing information, the OELCHECK consulting service, which is subject to a charge, can help. The same basic rules as for oils apply to the procedure for converting the grease previously used to a grease with H-1 approval.
Be sure to clarify the following questions:
- Are old and new grease compatible with each other? Mixing greases with different soap bases (e.g. lithium with sodium) can often make greases extremely soft.
- Does the grease need to be completely replaced and the bearing thoroughly cleaned, or is it sufficient to lubricate through or relubricate at shorter intervals?
- What about temperature stability at high temperatures?
- In most cases, H-1 greases have shorter relubrication intervals due to their structure. How often and how much grease needs to be relubricated?
- Is the grease easy to convey in central lubrication systems?
- Can used grease analyses contribute to operational reliability or clarify unanswered questions?
Lubricants that are NSFH1 certified are now available to supply machinery in the food industry, and they can also almost always perform as well as conventional products. Most lubricant manufacturers carry food grade products in their range, but not all have extensive experience or give an experienced consulting engineer the time to assist the customer with selection or conversion.
Please note: Follow our basic rules.
- Do not generalize hastily.
- Treat each machine and each application separately.
- If in doubt, seek advice from the independent OELCHECK experts.
- Check your machines with oil and grease analyses, especially during the changeover phase.
- Never place food contaminated with NSF-H-1 products on the market.