The use of oil-lubricated vacuum pumps often involves considerable dangers and costs in wood-processing companies. The reason for this is that these systems - depending on their age and maintenance status - release oil as a fine mist to the environment. This almost invisible oil mist subsequently deposits on all surfaces, especially on all semi-finished and finished products, in the workshop. Furthermore, oil-lubricated vacuum pumps may only be operated under vacuum, otherwise they will emit considerable amounts of oil.

Nowadays, oil-free production is of particular importance, as the many disadvantages of oil-lubricated vacuum pumps range from problems in surface treatment to health hazards.

The advantage of dry runners is: they do not cause any oil residue and oil mist, because they work OIL-FREE.

Oil-lubricated vacuum pumps need to be serviced regularly, otherwise their lifespan will be reduced or, in this case, even more oil will be released into the room air.

That means:

• oil level check, every 40 hours
• oil change, at least twice a year
• blow out soiled oil filter - if heavily soiled, filter change
• if necessary, cleaning or replacing of the air deoiling element every 1 - 2 years (depending on operation and dust load)
• If maintenance is neglected, there is an increasing risk of fire due to overheating of the vacuum pump and, subsequently, of the air de-oiling element.

MAINTENANCE COSTS of oil-lubricated vacuum pumps:

• Oil: approx. EUR 35
• air de-oiling element: ca. EUR 60 - 140
• Seal kits, shaft seal ring, etc.: depending on pump type
  
• Working time per maintenance: about 0.5 - 1 hours
• Disposal costs for oil: depending on the quantity
  

• oil lubricated vacuum pumps: 0.95 bar
  
• dry runner: 0.9 / 0.85 bar
  

However, this small pressure difference hardly has any significance in practice.

Of course it is right that the boiling point of the water drops in a vacuum.

The water in the glue boils faster under higher vacuum than under lower vacuum. The resulting steam, however, is trapped between the layers of material in the glue joint and must be absorbed by the materials — also as steam. Under certain conditions this can be a little faster than with the water in its liquid form. However, practical tests have shown that the difference hardly affects the actual drying time.

In summary it can be stated that the advantages of dry runners are significantly higher than the remaining - theoretical - advantages of oil-lubricated pumps.