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Old 12-17-2018, 06:13 PM   #1
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Bypass centrifugal filter

We have a Northern Lights 20kw genset on board (I know, it's big, but it came with the boat, brand new). I installed a Puradyn bypass filter on the main CAT 3306 a number of years ago, and have been meaning to install one on the genset as well. The basic reason is that OEM filters are designed to handle particles in the 20 - 40 micron range, but most wear on parts occurs from particles quite a lot smaller than that, or so I am told. A bypass filter simply supplements this stock filtration with a separate path for the oil to flow through that incorporates either a much tighter mesh in a filter cartridge, like the Puradyn that filters down to 1 micron, or via a centrifuge that spins the oil and separates particulates from the oil to about the same level - 1 micron. These particles collect on the side of the centrifuge and can be cleaned out at oil changes, or before if desired.

I thought some members might want an assessment of the difficulty, time and cost of installing a centrifuge as I can't see the downside of having cleaner oil.

The one I purchased for the 33 hp genset is from Dieselcraft, an OC 25. They make an OC 26 that covers 50 to 500 hp. The picture shows the unit as mounted. Oil comes under engine oil pressure enters the unit via the black hose and gets the centrifuge spinning around 6,000 rpm. Another port sprays oil on the inside of the spinning centrifuge, and separates rubbish from oil, which flows out the top of the unit, and drains back to the sump via the blue hose. The little silver box to the left is a small air pump Dieselcraft supplies to help push the oil back to the sump so the drain hose can be small i.d. They told me the unit process about .4gpm of oil.

The unit comes with the bracket shown that allows it to be mounted on any angled surface. They supply some hose, and all the fittings needed to make up the connections. You need to locate a source of 12 vdc power for the pump that is only on when the motor is running. In the NL's case, I could make a connection at the engine kill unit that is activated by the various Murphy switches on the engine. It is a normally closed switch that opens and stays open as long as the engine is running and no low oil pressure or high temperature condition is detected. You tap into the pressure side of the oil path in the engine - usually these taps can be found near the oil filter - and connect the supply line. The return line can be more problematic. In my case, I have the sump of the NL plumbed to an oil extraction pump for oil changes, so it was easy to pipe into that, but absent that, tapping and drilling the oil cap, or worse, the pan itself might be needed. The whole installation took me about 4 hours. Cost for the filter is $420 delivered, plus a few extra parts for plumbing.

The only tricky bit was finding a metric to pipe adapter, but Amazon came to the rescue. The tap on the block of the NL unit is an M10 x 1.0, and all the fitting for the Dieselcraft are pipe fittings.

The OEM filter on the NL is really small, and I suspect that may be why the oil change interval is 100 hours. While they say you can significantly extend oil change intervals with any bypass filter, I have never done so. Oil seems cheap compared to the cost of repair, so saving $100 once a year in oil I could have kept doesn't seem material enough to worry about, given other boat expenses.
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Old 12-17-2018, 08:34 PM   #2
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What a neat idea and nice installation. What is the primary target audience for the unit? Also, in the event of power loss to the unit does the normal oil flow and filter perform as normal?
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Old 12-17-2018, 08:47 PM   #3
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Carl
What a neat idea and nice installation. What is the primary target audience for the unit? Also, in the event of power loss to the unit does the normal oil flow and filter perform as normal?
From their website, it looks like they sell a lot of units to diesel pick up truck owners. On Youtube there are a couple of videos done by truck owners who are somewhat surprised at how much crud the units separate out. This small one they don't even list on their website, so I assume they don't have much of a market, but I don't see why it wouldn't work on any small genset diesel.

I asked about gravity only for draining back to the sump, and they said you would need a 1/2 i.d. line. Without the air pump, which they say is good for 20,000 hours, the amount of oil in the bottom of the unit would probably build up to the point where it would stall the centrifuge, so I suspect it just wouldn't work, but no harm would be done. Further, this little unit drains half of what the larger one they sell for 50 to 500 hp but uses the same 5/16" i.d. drain line, so maybe it would still work. Beats me. I'll be curious to see what gets collected after 20 hours or so.
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Old 12-17-2018, 08:53 PM   #4
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Correction to the model number. What I have is an OC-26, which is smaller than the OC-25.
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Old 12-17-2018, 10:11 PM   #5
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The centrifuge uses engine oil pressure to power spin. Higher oil pressure, faster spin, more/smaller particles removed. So if you can boost the oil pressure to the centrifuge you get better cleaning. I've played with bypass filters since the 1960s. When running engines just like others were using, my engines went almost twice as many hours between rebuild.

I used one of these years ago, but went to a stand alone centrifuge that spins faster and does all the engines. Now I get transparent oil.
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Old 12-18-2018, 06:23 AM   #6
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It would seem that spinning the centrifuge with oil is the most common practice , although so little energy is required an electric motor might work better at even at idle,full cleaning speed would be obtained.

The larger OTR trucks have oil powered models that are serviced by replacing a paper filter like a coffee filter at tiny cost or effort.

The truck units are not white boat priced , BUT the mfg would not allow the unit to filter diesel fuel.
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Old 12-18-2018, 06:52 AM   #7
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While I like the idea, I wonder if it masks engine problems. I do oil analysis at each oil change. Mostly I'm looking for wear metals, fuel, water and antifreeze in the oil. Does this process remove those things? While obviously I don't want them in the oil, I do want to know if something is wearing abnormally or if a gasket between oil and antifreeze is weeping.

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Old 12-18-2018, 09:24 AM   #8
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While I like the idea, I wonder if it masks engine problems. I do oil analysis at each oil change. Mostly I'm looking for wear metals, fuel, water and antifreeze in the oil. Does this process remove those things? While obviously I don't want them in the oil, I do want to know if something is wearing abnormally or if a gasket between oil and antifreeze is weeping.

Ted
It will certainly remove particles from around 1 micron to around 30 - 40 microns, and ones larger than that will get caught by the OEM filter. But I beleve that oil analysis is done with a gas spectrometer and if you have excess wear it will still show up because the particles are smaller than 1 micron. I've read that most wear comes from particles around 7 microns, which are simply passed through by the OEM filter.

In any case, I'm not sure of the benefit of having dirty oil so it is easier to see that it's dirty....
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Old 12-18-2018, 09:26 AM   #9
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It would seem that spinning the centrifuge with oil is the most common practice , although so little energy is required an electric motor might work better at even at idle,full cleaning speed would be obtained.

The larger OTR trucks have oil powered models that are serviced by replacing a paper filter like a coffee filter at tiny cost or effort.

The truck units are not white boat priced , BUT the mfg would not allow the unit to filter diesel fuel.
Diesel craft does sell stand alone motors and adapters for that purpose.
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Old 12-18-2018, 10:58 AM   #10
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I don't understand what problem this solution is fixing? If you change the oil at the recommended intervals and at the rate we use them, most engines will outlive most of us.

Cute thing though, fun gadget.
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Old 12-18-2018, 11:01 AM   #11
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I don't understand what problem this solution is fixing? If you change the oil at the recommended intervals and at the rate we use them, most engines will outlive most of us.

Cute thing though, fun gadget.
No doubt they will. However, since most all wear related to lubrication happens with particles that pass right through the OEM filter, arguing against bypass filtration is arguing for engine wear and dirtier oil.

Kind of like cleaning the boat. You don't need to as dirty boats don't sink any faster than clean ones, but you do anyway.
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Old 12-19-2018, 05:54 AM   #12
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As any engine ages from wear it looses efficiency

It gulps more fuel from worn sloppy or stuck rings and becomes harder to start .

It may become louder as internal slop increases .And will usually smoke more.

None of the wear adds to the pleasure of boating , even if the engine does last for 40 years.
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Old 12-19-2018, 08:30 AM   #13
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Sorry, I don't see it. I can see using it if you are running your boat commercially or have a depreciation concern but for recreational boaters? But like every other type of boat voodoo like anchor size or synthetic oil or stern thrusters, you will do whatever your dad did, or your buddy does and you will be content.

What's wrong with that?
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Old 12-19-2018, 09:47 AM   #14
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Sorry, I don't see it. I can see using it if you are running your boat commercially or have a depreciation concern but for recreational boaters? But like every other type of boat voodoo like anchor size or synthetic oil or stern thrusters, you will do whatever your dad did, or your buddy does and you will be content.

What's wrong with that?
Reduced engine wear and maintaining your stuff is boat voodoo?
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Old 12-19-2018, 09:57 AM   #15
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As any engine ages from wear it looses efficiency

It gulps more fuel from worn sloppy or stuck rings and becomes harder to start .

It may become louder as internal slop increases .And will usually smoke more.

None of the wear adds to the pleasure of boating , even if the engine does last for 40 years.
Like most families, we pass on vehicles to our kids when they still run, but are basically no fun to drive anymore. The last one was a VW Passat. Ran for another 50,000 miles after I have it away. Mine you, my son had to enter it via the trunk for the last 10,000 since the door handles didn't work anymore.

Some people like to maintain their things to a high level and some don't, knowing they still work, more or less. To each his own.
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Old 12-19-2018, 10:35 AM   #16
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No doubt they will. However, since most all wear related to lubrication happens with particles that pass right through the OEM filter, arguing against bypass filtration is arguing for engine wear and dirtier oil.
I think most wear due to particles that get through the filter are, well, particles that get through the filter. If the OEM paper filter bypasses 7 micron particles, and these are really responsible for most of the wear, then one could save money by not fitting them at all. I'd like to see those studies.

That said, it's hard to argue against clean oil. And to the poster saying "why?", I'd agree on a plain white clorox bottle production boat, Delfin is anything but that. No one is going to throw it away when the engine is worn.
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Old 12-19-2018, 11:06 AM   #17
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I think most wear due to particles that get through the filter are, well, particles that get through the filter. If the OEM paper filter bypasses 7 micron particles, and these are really responsible for most of the wear, then one could save money by not fitting them at all. I'd like to see those studies.

That said, it's hard to argue against clean oil. And to the poster saying "why?", I'd agree on a plain white clorox bottle production boat, Delfin is anything but that. No one is going to throw it away when the engine is worn.
Since she has already out lived one diesel, and since changing engines is a matter of cutting a barn door in her side so you could get it out, you're right.

The OEM filter removes larger agglomerated carbon particles that the additives in the oil encourage to stick together so they are large enough they can be picked up. So there is no argument for removing it just because you have a by pass filter. You can make the argument for not changing it as frequently, just as pre-filtering diesel will extend the life of the OEM fuel filter. It's just a question of whether it's worth the money to you. For me, not so much.

Here's a study on particle size and wear: https://p2infohouse.org/ref/31/30453.pdf

If the wear particles in the oil are smaller than the lubrication film thickness, then no wear occurs. Table 2 in the above shows what thickness that film is on different parts of the engine. Get the smallest particle size in the oil to one micron or so and you will eliminate most wear particle caused engine wear.
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Old 12-19-2018, 01:17 PM   #18
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Why wouldn't you mount the filter with the can on the bottom, for cleaner oil changes?
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Old 12-19-2018, 01:38 PM   #19
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Why wouldn't you mount the filter with the can on the bottom, for cleaner oil changes?
I'm not sure I understand the question...
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Old 12-19-2018, 02:01 PM   #20
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In the image posted earlier, the canister is bulkhead mounted with the can on top. How do you change the filter unit without dripping the contents? Drain it back in the sump?
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