Oil purification 1

Since nobody has responded yet, I'll throw my comments out there. I'm not an expert in this area, but I do have experience with centrifuges and small lube systems.

Since you say this is a large capacity application, centrifuges is an alternative, of course depending on your requirements. The centrifuge can run continuously separating out the solids as well as any water that has accumulated. Centrifuges come in two main styles, solids bowl and desludging types. If your solids level is low, then a solids bowl may be the better choice (cheaper cost and maintenance), but the machine has to be stopped and cleaned periodically which increaes your operations and maintenance costs. The desludging machines automatically clean themselves, so can keep running, but cost more and require more controls to operate.

Centrifuges typically have a higher capital cost then other systems and must have routine maintenance, which also increases their cost, but a centrifuge can usually fit in a smaller space then a filtering system of the same capacity. Typical overhaul intervals are about 5-6000 hours, but the newer types are supposed to go much longer then that. The cost of filters may outpace the centrifuge if you have alot of solids in the lube oil.

Is this for a product you are selling or in your plant? If for your companies use and cost is a big issue, there are many used centifuges on the market that will bring the cost down significantly.

Mike Bensema

I would think your suppliers of the filtering
devices would have test results of their product.
There must be some base standard that they are
all using for comparison.

There are good, inexpensive canister-type oil filters readily available for removing particulates (and water) from oil. General concepts to design into your systems:

High viscosity oils require more filters, operated in parallel to get adequate flow. Filter manufacturers often design for diesel fuel viscosity (which are most of there sales). Flow and pressure-drop design information for 320, 460, and 680 weight oils are difficult to find, but fairly easy to test. If I remember correctly, 1.5 GPM will flow through a modern 10 micron filter canister, with a 20 psi pressure drop. Older filter media fabrics won’t flow nearly as much.

Old gearbox designs had brass screens (150 micron), if any filtering. Good quality, old gearbox drives from the 1950’s used 40 micron filters, and now the best OEM gearbox manufacturers filter oil on their large drives to 20 micron. For most gearbox applications, 10 micron on-line filtering is optimum. 10 micron won’t filter out most EP oil additives and will remove the bulk of damaging particulates.

Include an over-pressure bypass device for plugged filters (the “can” on a canister filter can handle about 300 psi). I used a 150 psi, in-line rupture disk, and it worked well.

Use a SS screen filter canister (100 micron) prior to the oil pump to keep out the “rocks and rabbits”. You’ll be amazed – in normal application it will rarely (if ever) plug, which indicates most debris in normal gearbox applications are less than 100 micron.

Use an oil flow switch to further protect your equipment.

Include an oil sample valve.

Design your oil piping on CAD – it makes the installation easier and better.

Example: Four 12 micron canister filters on a 600 hp gearbox plugged within two hours after a “clean” overhaul. The filters plugged a second time after 2 days, a third time after 2 weeks, and a 4th time after 2 months. Obviously lots of small dust-size crap was in the 300 gallons of oil, even after the crews did their very best to clean the equipment.

Look at used filter debris under a microscope – you can learn a lot about your equipment and environment.

Call if you want to discuss particular applications. Paul Juhnke, 641-423-9363

I am not sure why you are having problems with particulates I suspect that it may be because of water content above 100 ppm. Water causes corrosion, is a catalyst for sludge formation, depletes additives, and leads to bacterial colonies. You need to get your water down below 100 ppm. My favorite technology for dehydration is air stripping technology because I think it is superior to centrifuges, filters, and vacuum dehydration, for many reasons.