Oil/Water Separator

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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Oil/Water Separator

Post by TriangleTom » Sun Apr 08, 2018 2:20 pm

Those of you running condensing plants, what do you do do remove oil from the condensate before sending it back to the boiler?
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Re: Oil/Water Separator

Post by fredrosse » Sun Apr 08, 2018 4:26 pm

To remove oil from water, you must use an oil that does not emulsify with water, once it is emulsified, you cannot remove the oil, unless you boil away the oily water, leaving the oil behind, but that does not generally work on a steamboat. Pure Mineral oil is separable from water, virtually any typical motor oils or compounded steam cylinder oils will form an emulsion, and oil will end up in your boiler if you use motor oils or compounded steam cylinder oils.

There are many successful arrangements of hotwells to catch exhaust condensate oil, (provided it is NOT emulsified with water), usually several chambers where the condensate enters near the top, oil floats upward, water travels downward and into the next chamber. Filter material absorbs any remaining oil, then the water feeds into the next filter chamber, etc. Good filter material can be paper towels (economy method). WWII Liberty ships used excelsior or lofa sponges. Today steamboaters are having success with marine oil absorbing pads, sold for the bilges of motorboats.

What size steam plant do you have?
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Re: Oil/Water Separator

Post by TahoeSteam » Sun Apr 08, 2018 4:40 pm

We try to use an absolute minimum amount of oil necessary. We have a large hotwell with three compartments that communicate through holes on the bottom of the partitions. Condensate discharge on one end and the feed intake way on the other end of the hotwell. We use pigmat brand absorbant pads designed to absorb only oil as well as lufa sponges in each of the three compartments. The compartment that has the condensate discharge has a slight oily film on it, the one in the middle and the one with the feed intake have zero film in them. After WELL over 50 years of collective steamboating experience between my father and I we've found that the pigmat oil-only products have worked the best for us
https://www.newpig.com/oil-only-absorbe ... ads/c/5002
https://www.newpig.com/oil-fuel-absorbe ... ncQAvD_BwE
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Re: Oil/Water Separator

Post by Lopez Mike » Sun Apr 08, 2018 5:03 pm

I would echo the previous posts only with some added emphasis to the idea that you should think carefully about whether you need internal lubrication. Superheating? Yes. Poor compatibility between sliding surfaces? Yes.

But many of our engines are all cast iron on cast iron with saturated steam and running at relatively low speeds and loadings. No lubrication really needed.
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Re: Oil/Water Separator

Post by TriangleTom » Sun Apr 08, 2018 9:15 pm

fredrosse wrote:To remove oil from water, you must use an oil that does not emulsify with water, once it is emulsified, you cannot remove the oil, unless you boil away the oily water, leaving the oil behind, but that does not generally work on a steamboat. Pure Mineral oil is separable from water, virtually any typical motor oils or compounded steam cylinder oils will form an emulsion, and oil will end up in your boiler if you use motor oils or compounded steam cylinder oils.

There are many successful arrangements of hotwells to catch exhaust condensate oil, (provided it is NOT emulsified with water), usually several chambers where the condensate enters near the top, oil floats upward, water travels downward and into the next chamber. Filter material absorbs any remaining oil, then the water feeds into the next filter chamber, etc. Good filter material can be paper towels (economy method). WWII Liberty ships used excelsior or lofa sponges. Today steamboaters are having success with marine oil absorbing pads, sold for the bilges of motorboats.

What size steam plant do you have?
Fred, thanks for the very detailed answer. I don't have a plant or boat yet, but I've been reading through Audel's Engineering Handbook and Audel's Heat And Power Engineering and the sections on condensate treatment were pretty confusing on the topic of oil removal especially.
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Re: Oil/Water Separator

Post by RGSP » Mon Apr 09, 2018 8:35 am

As mentioned by others, using minimal oil, and then only a non-elmulsifying sort, are the two first steps, with hotwell design third.

Many steam enthusiasts in England use nappy (diaper?) liners (intended for small babies) to absorb oil from the hotwell water. They may not be the best possible oil absorbers, but they do work very well, are very cheap and easily available, and can be disposed of frequently and safely. I hope those words translate sensibly from English into American: it's not a subject I want to dwell on if possible.
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Re: Oil/Water Separator

Post by TahoeSteam » Mon Apr 09, 2018 5:40 pm

RGSP wrote:As mentioned by others, using minimal oil, and then only a non-elmulsifying sort, are the two first steps, with hotwell design third.

Many steam enthusiasts in England use nappy (diaper?) liners (intended for small babies) to absorb oil from the hotwell water. They may not be the best possible oil absorbers, but they do work very well, are very cheap and easily available, and can be disposed of frequently and safely. I hope those words translate sensibly from English into American: it's not a subject I want to dwell on if possible.

As an illiterate Californian I could understand you... Though im sure my mother being from Manchester certainly helps.
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Re: Oil/Water Separator

Post by DetroiTug » Mon Apr 09, 2018 5:48 pm

Quote: "enthusiasts in England use nappy (diaper?) liners (intended for small babies) to absorb"

Aye, nappy's for the wee wains. :)

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Re: Oil/Water Separator

Post by Lionel Connell » Tue Apr 10, 2018 2:36 am

Is there any (reasonable) means of catching any of the oil between the engine and the condenser? i.e. reducing the amount of oil that goes through the condenser?


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Re: Oil/Water Separator

Post by Lopez Mike » Tue Apr 10, 2018 3:05 am

I as far I know, all of the schemes to separate oil from water depend on stagnation. The only places in the cycle where there is any significant stagnation are the condenser and the boiler. And, as far as I know again, it doesn't hurt the condenser to have some oil in there.
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