@jbierling said:
How is your bath heated? What kind of oil?
My bath is used for calibrating temperature sensors above 100degC, it has nothing to do with distilling. But anyway, the bath is heated the same way as those fancy kettles with the element embedded in the bottom of the kettle. We use engine oil, Castrol GTX in the bath, vegetable oils leave a sticky residue on the bath and the probes.
@Mickiboi is your element directly exposed to the oil at all?
I find it interesting how many different recommendations there are for heating transfer fluids. Plain old water (its been suggested vapor pressure never rises too high), mineral oil, vegetable oil, general use frying oil, peanut oil, glycol and now motor oil. Maybe all the oils pretty much work equally well which is why there are so many recommendations. I think one real difference is the smells, but it seems to me that given the oil would be sealed, that there shouldn't be much smell.
My thought at the moment is to try water and vent either manually at 10psi or through an automatic safety valve at 15psi. If water doesn't work out, its easier to dump it and try oil rather than the other way around.
@jbierling said:
My thought at the moment is to try water and vent either manually at 10psi or through an automatic safety valve at 15psi. If water doesn't work out, its easier to dump it and try oil rather than the other way around.
Yes, that would be the way to go. Here in Austria nobody we've met so far has anything other than plain water in his bain-marie still. The specification for a bain-marie is to be found in the Austrian Alcohol Tax Law, which lists "Waterbath up to 0.5 bar" or "Oilbath" as the only allowed options (means steam is not possible here in the "farmers" class up to 150L boiler volume).
All the stills up to 150L we have seen from the large commercial builders (Carl, Kothe, Holstein,...) use only water in their waterbath, a gauge with a red mark at 0.5 bar and a safety pressure valve for 0.5 bar. They are mostly heated by wood-fire and driving them hard (means lots of fire) never seems to exceed about 0.4 bar (though we've heard some stories about having a 0.6, 0.8 or even 1 bar valve at hands somewhere hidden in a closet for swapping and getting it maxed out with a nice little hell fire). Pretty much nobody uses anything other than a bain-marie with agitator around here.
StillDragon Europe - Your StillDragon® Distributor for Europe & the surrounding area
There are slightly different interpretations of bain-marie - particularly to the home builders.
Many home built bain-marie boilers have the internal pot loose from the outer pot, and the seal between the two is maintained by weight or by clamps. There tends to be slight leakage of oil vapor or water vapor into the still room, which can be inconvenient. As these are unsealed (and even if sealed they have an open fill / expansion vent) then they can not be above atmospheric pressure.
In this situation the oil can be maintained at higher temperatures than water. If you use water there is also a tendency to turn your still room into a sauna because of the steam leakage.
With the jacketed boilers that are bain-marrie style, the water is used at up to 0.5 bar HIGHER than atmospheric pressure and this increases the working temperature.
I used to say that you should not home build a pressurised boiler, although I would now qualify this to say that if you were competent and sensible, then you could probably manage to do the sort of boiler mentioned above. Less than 1 bar, with safety devices, and a bit of common sense.
I still maintain you should not try a 3 bar self build, unless you have the professional skills to do so.
Comments
How is your bath heated? What kind of oil?
My bath is used for calibrating temperature sensors above 100degC, it has nothing to do with distilling. But anyway, the bath is heated the same way as those fancy kettles with the element embedded in the bottom of the kettle. We use engine oil, Castrol GTX in the bath, vegetable oils leave a sticky residue on the bath and the probes.
need to find some Castrol R..... or Klotz.... nothing like the smell of bean oil..... at least in a racing two stroke!
@Mickiboi is your element directly exposed to the oil at all?
I find it interesting how many different recommendations there are for heating transfer fluids. Plain old water (its been suggested vapor pressure never rises too high), mineral oil, vegetable oil, general use frying oil, peanut oil, glycol and now motor oil. Maybe all the oils pretty much work equally well which is why there are so many recommendations. I think one real difference is the smells, but it seems to me that given the oil would be sealed, that there shouldn't be much smell.
My thought at the moment is to try water and vent either manually at 10psi or through an automatic safety valve at 15psi. If water doesn't work out, its easier to dump it and try oil rather than the other way around.
Yes, that would be the way to go. Here in Austria nobody we've met so far has anything other than plain water in his bain-marie still. The specification for a bain-marie is to be found in the Austrian Alcohol Tax Law, which lists "Waterbath up to 0.5 bar" or "Oilbath" as the only allowed options (means steam is not possible here in the "farmers" class up to 150L boiler volume).
All the stills up to 150L we have seen from the large commercial builders (Carl, Kothe, Holstein,...) use only water in their waterbath, a gauge with a red mark at 0.5 bar and a safety pressure valve for 0.5 bar. They are mostly heated by wood-fire and driving them hard (means lots of fire) never seems to exceed about 0.4 bar (though we've heard some stories about having a 0.6, 0.8 or even 1 bar valve at hands somewhere hidden in a closet for swapping and getting it maxed out with a nice little hell fire). Pretty much nobody uses anything other than a bain-marie with agitator around here.
StillDragon Europe - Your StillDragon® Distributor for Europe & the surrounding area
No mate its embedded in the base of the bath, it never gets exposed to the oil.
There are slightly different interpretations of bain-marie - particularly to the home builders.
Many home built bain-marie boilers have the internal pot loose from the outer pot, and the seal between the two is maintained by weight or by clamps. There tends to be slight leakage of oil vapor or water vapor into the still room, which can be inconvenient. As these are unsealed (and even if sealed they have an open fill / expansion vent) then they can not be above atmospheric pressure.
In this situation the oil can be maintained at higher temperatures than water. If you use water there is also a tendency to turn your still room into a sauna because of the steam leakage.
With the jacketed boilers that are bain-marrie style, the water is used at up to 0.5 bar HIGHER than atmospheric pressure and this increases the working temperature.
I used to say that you should not home build a pressurised boiler, although I would now qualify this to say that if you were competent and sensible, then you could probably manage to do the sort of boiler mentioned above. Less than 1 bar, with safety devices, and a bit of common sense.
I still maintain you should not try a 3 bar self build, unless you have the professional skills to do so.