Centrifuge and heat or gas to get it spinning?

[camp9]

I recently bought a 65gph centrifuge. Takes a while for it to get up to speed when oil is cool. Is this the nature of the beast? I'm thinking of adding gas to thin it down instead of heating too. Anyone doing this? I can already see a bigger one is in order Thanks.

 

[PsycoBob]

I'd rather heat it- why waste part of the centrifuge's gph rating on clean gas?

I'm thinking you mean 65gph- 65gpm would need a huge pump to keep the pressure up. If the oil's cold, the pump motor may not be able to make it's rated RPM, or the pump may have an internal bypass that's opening from excessive pressure. Cold oil will give huge pressure drops just in a few feet of hose & fittings- the centrifuge may be seeing 1/2 of what the pump's making. It'll also give very slow flow from the rotor's jets, slow flow into the rotor, etc. Frictional losses around the rotor's shaft will be substantial as well.

I have a system based on a Spinner II 76se, a 2.5gpm rated centrifuge. I don't bother turning the pump on until my drum heater's at 100 or higher. If you're using an inline heater, adding a ball-valve bypass to recirculate the oil until it's warm might be an idea.

When I changed my operating temp from the manufacturer's recommended 130 to 200, I got 3-5 times as much accumulation in the rotor. The limit on temperature in my system is the o-ring between the rotor bowl & base, as everything else is rated 300+ or metal. Next time I pull the rotor for cleaning, I'll be measuring the oring, so I can find a replacement, hopefully in a higher temp rating.

 

[gimpyrobb]

Yeah, heat is the key. It will not flow enough to get the rated speeds cold.

 

[camp9]

Yep, your right and I fixed my typo, it's 65gph. Just seems like even when its hot and spinning just fine, I'll shut it down to clean it out, put it back together about 10 minutes later and seems like it just won't go, take it apart again and re-clean the nozzles and still not go, then next time on cool oil it will be up to speed in a few minutes. I'll just make sure the oil is hot and keep playing to find the right combination.

 

[PsycoBob]

With hot oil, after shutting down the pump to clean the bowl, restarting takes maybe 30 seconds to full speed. I usually lower the relief valve's setting before shutdown & readjust once the pump's running hot oil again- takes about as long to flush the lines as it does to turn away from the switch & grab the rag to keep from burning myself on the relief valve.

Do you have a pressure/temp gauge on the line feeding the centrifuge? Mine's intended for a steam table or some such, found it cheap on eBay. My centrifuge had a valve to keep from starving the engine of oil- disabling it improved performance.

I found that at the rated temp a pump rated for well over the centrifuge's flow rating was needed to maintain pressure, but there was a fine line between making enough pressure & having my relief valve dumping oil back into the drum. Looked like a lot, maybe once I'm running again, I'll measure it.

I'm honestly not sure if the small centrifuges have a relief valve built-in instead of a low-pressure safety cutoff like mine did. The Spinner units even have a cute reverse-toilet-float thing going on- they use the truck's air supply to pressurize the outer housing slightly, to keep force the 'clean' oil down the drain to the crankcase. The float maintains just enough air input to keep the oil below the rotor.

 

[G-Force]

Lube oil separating temps should be between 194-212 F (90-100C) to get a good separation. This is for detergent oil which is probably what everybody now days is running. When you get into non-detergent the temps are a little lower but not much.....
If you run it cold you're wasting your time.
And adding gas will just make the gas vaporize when it gets discharged from the rotor and just create alot of fumes for you....so no smoking.....

 

[camp9]

Do you have a pressure/temp gauge on the line feeding the centrifuge? Mine's intended for a steam table or some such, found it cheap on eBay. My centrifuge had a valve to keep from starving the engine of oil- disabling it improved performance.

I have a pressure gauge, no temp. I'll have to look for one of those gauges, sounds handy. I've been putting it on the south side of our machine shed with a black tarp behind it. It's been getting pretty hot during the day, but don't know the temp. I'll check it with the infrared temp gun tomorrow. From what your saying it's not hot enough which makes since. It's hot, but not so hot that I have to be careful about touching it. Time to put some heat to it and give that a try. Thanks