So from all this I presume that as far as the "crucial" 68deg. F temperature goes that if the test is done at temps under 68 that this should cause more fall out (sort of a worse case scenario) & if the test is done at higher temps this should keep more unconverted oil (if any) in solution, therfore less fall out? Also how long is the time period that all this is supposed to occur in ie: how long is it necessary to maintain 68F?
Thanks. P

Yes, high temps cause low conversion fuel to appear to pass and low temps cause good fuel to appear to fail.

I like to do my final check on the test at 30 min. maintained at 68f in a sealed jar in a water bath.

HTH.

quote:

Originally posted by PD.Vancouver:
Can anyone here explain what variables exist that perhaps I may not be controlling properly

PD, I won't mention temperature again, as it has been covered well enough, but I did have a period when I started failing 3/27 tests, even when I carefully controlled the temperature. In this case I suspect the problem was that the methanol had absorbed moisture from the air. When I mixed up the 3 ml of bd in the 27 ml of methanol it became quite cloudy and i would get small droplets of oil dropping out. When I got the same results after reprocessing I tried fresh methanol and the BD passed easily. So make sure your methanol does not absorb water by keeping it in a tightly sealed container.

Methanol that has been exposed to air can indeed cause a false fail of this test. It will not however cause variation from test to test, unless the methanol had different amounts of contamination.

quote:

Originally posted by Biotom:
Andrew
-this past summer I seen biodiesel made from bacon fat. at amient temp, that day, was 28C there was a white solid layer on the bottom of the sample about 3/16 of an inch thick (high melt temp esters). this biodiesel passed the GC tests. I can just imagine what 3/27 would looked like on that stuff even at 68f.

That would be very unusual to see Biodiesel from Bacon Fat to have a melting point as high as 28C. Even the hardest animal fats tend to produce biodiesel with a melting point below 20C.

I too would be interested to see the results from the ASTM test on that fuel as it sounds quite strange for there to be so much solid at such a high temperature (unless it had just come out of a fridge when you saw it).

quote:

Even the hardest animal fats tend to produce biodiesel with a melting point below 20C.

My experience too. And, if well converted, they will pass 3/27 with no problem at 20C/68F. In my experience.

I've found it usually take more like an hour plus before the 3/27 test reveals results. The alcohol usually goes thru a mirky phase then after about 45 minutes to an hour or more it will turn clear again with any fall out, or not. Is this not how it works for others?
P

quote:

I've found it usually take more like an hour plus before the 3/27 test reveals results. The alcohol usually goes thru a mirky phase then after about 45 minutes to an hour or more it will turn clear again with any fall out, or not. Is this not how it works for others?

I have never done the test at temps. much above 68f. That could be a factor in taking more time. Also, what size do you do the test? Is your jar tall and thin? Is it sealed?

In my testing, it always cleared in 30 min. or less. If there was going to be fallout, 30 min. was enough for that to show. But, the sequence you describe is what I see. Except for with clean passing fuel, then it is clear right away with no cloudiness.

quote:

Originally posted by PD.Vancouver:
The alcohol usually goes thru a mirky phase then after about 45 minutes to an hour or more it will turn clear again with any fall out, or not. Is this not how it works for others?
P

I experienced this earlier from the same batch of methanol that later produced the false negatives and would not clear. If your BD is relatively dry, it should clear up quite quickly, (a couple of minutes..) I now draw fresh methanol from the drum for this test.

Well I'm usually pretty conscientious (fussy) about the process & all ingredients etc. I use a small, about 100 ml sealed bottle (small jam jar type), always careful about keeping lids on all chemicals, dry BD & to do processes in a repeatable way, properly to the T, & try to do the test when conditions are at 68F but sometimes get varying results. Just trying to get some answers from others to be able to "compare notes".
P

As mentioned by TDIGuy, the purity of the methanol seems to affect the outcome of the test. Methanol that has been exposed to air can cause false fail results to appear.

I suggest two things to keep tests consistent:

use yellow heet as you methanol and keep the jar closed at all times.

use a water bath to control the temp of the test jar with measured methanol in it. Even better, put the bd in the water bath too. Keep the bath at 68f for 30 min prior to the test and then for 30 min during the test.

HTH.

What is your technique for maintaining 68F in the water bath for an hour?
P

My water bath is a large flat tupperware. I start with the water at 68f. If the air is hotter than that, I gradually add a bit of ice cold water, in amounts small enough to keep the temp. at 68f +/- 1 degree. If it is cooler, I add a bit of hot water. If the ambient temp. is extreme, I use a bigger container. I rarely have to add water more than once or twice.

HTH.