Test Methods for Water in SVO

Collecting, filtering and dewatering of WVO SVO vegetable oil. For Biodiesel producers too.

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Test Methods for Water in SVO

Postby John Galt » Sun Mar 09, 2008 11:36 am

Water in vegetable oil and biodiesel exists in three phases. One is dissolved water, which is characterized by individual water molecules dispersed throughout the oil. Dissolved water in oil is similar to humidity in the air - the water is there, but it is too small to see because it is dispersed molecule-by-molecule. Thus SVO or biodiesel can hold a significant concentration of dissolved water and still appear clear. Most vegetable oils can easily hold 200 to 600 PPM of water (0.02 to 0.06 percent) in the dissolved state depending on the temperature and age of the oil. Used oils can hold three to five times more water in the dissolved state than new oil.

Oil becomes saturated with moisture when the amount of water exceeds the maximum concentration for it to remain dissolved. In this second phase, the water is suspended in the oil in microscopic droplets known as an emulsion. This is like fog on a cool, spring day. In that case, the amount of moisture in the air is greater than the saturation point, and a suspension of small droplets of moisture or fog results. In SVO or biodiesel, this “fog” is often referred to as haze and the fuel is called 'cloudy' or 'hazy'. Haze usually indicates moisture above 1500 PPM [0.15%] at 'room' temperature. Therefore SVO or biodiesel that appears clear may not necessarily be dry enough for use as motor fuel.

The generally acceptable amount of water in SVO or biodiesel fuel is 500 PPM or 0.05 percent.

Adding more water to an emulsified mixture will cause a separation of phases to produce a third phase of free water as well as the dissolved and suspended water. This is similar to rain falling when the amount of moisture in the air exceeds the dew point. This free water is usually found on the bottom of containers of used SVO, where it's mixed in with the fatty sludge and food particles. If free water is evident then it's likely that dissolved and suspended water is also present in the SVO or biodiesel.

Testing for water in Vegetable Oil or Biodiesel:

Image

The Crackle Test or Hot Pan Test

Heat a pan to 320°F (130°C), then add a drop of oil in the center. Moisture in the oil is indicated by the number of bubbles seen when the water boils off. A few small bubbles is about 500 to 1,000 ppm (0.05 to 0.1 percent) water. More bubbles of a larger size show approximately 1,000 to 2,000 ppm water, and a crackling sound is evident if moisture levels are in excess of 2,000 ppm. The Crackle Test is reportedly only sensitive to free and emulsified water.

A variation of this method is the Hot-Pan-Test
http://www.vocontrol.com/wiki/Pan_Test
The "Hot Pan Test" is a quick, unscientific and non-quantitative test to check for the presence of water in vegetable oil [SVO]. The HPT is similar to the Crackle Test, but uses a larger sample. These videos illustrate the HPT procedure.
http://www.youtube.com/watch?v=0ChUkpeZuow
http://au.youtube.com/watch?v=2Cs6mo85Cfg

The HPT is not "foolproof" by any means. False positives can be obtained if the pan is WAY too hot or if solvents are mixed in the SVO. False negative results are possible if the sample contains suspended water that has high concentrations of salt/sugar/acids.

Another variation is the hot spoon test. It's quicker, uses much less oil and is much easier to clean up while producing the same results. It uses a teaspoon, a tablespoon, a plumbers propane torch and paper towel over the sink. Smear a little oil on the tablespoon and heat it over the propane flame till it begins to smoke. Use the teaspoon to scoop 1/2 a teaspoon of oil to test and pour it into the hot tablespoon. Look for bubbles as per the hot pan test. Dump the hot oil on the paper towel, rinse in water to cool. Wipe the spoon with paper towel and it's ready for the next test. The same limitations as the HPT apply.

A method that can be used on VO/diesel blends is the Weigh/Heat/Weigh method. It works to quantify the percent moisture in a sample of fuel. The larger the sample the more accurate the test, 250ml is the minimum amount for a common 1/10 gram scale. This is a standard moisture test commonly used in the agriculture industry. It can be used for VO, diesel fuel, or mixes of the two, but won't work with mixes containing volatile solvents.

One can also use a metal container and a hotplate instead of a microwave to heat the fuel. In this case the thermometer can be left in for all the weight measurements. This reduces the error from oil removed with the thermometer. Using a non contact IR thermometer would be better. This hot plate variation can be better for testing blends where the solvent smell could otherwise stay in the microwave and cause concern with other users heating food.

Another method: the Sandy Brae water test. Expensive but accurate.
http://www.sandybrae.com/watertest.htm

A DIY version of this is the "Carbide Manometer"
http://make-biodiesel.org/Quality-Testi ... rbide.html

The recognized industrial standard is:
ASTM E203 - 01 Standard Test Method for Water Using Volumetric Karl Fischer Titration
http://www.astm.org/Standards/E203.htm
Many oil analysis labs offer this test.

Additional water testing analysis information at:
http://www.machinerylubrication.com/Rea ... l-analysis

This discussion is for methods to measure water in SVO, and feedback on the methods to measure moisture content.
Last edited by John Galt on Thu Jun 21, 2012 1:48 am, edited 33 times in total.
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Postby jordanmills » Sat Mar 15, 2008 5:07 pm

Well that explains why I'm getting bubbles on the HPT when my stuff is clear and dry. Must be that I still had some diesel in the barrel I used to collect.
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Postby SunWizard » Sat Mar 29, 2008 6:44 pm

(edit:) Now that I have bought and compared most of the water testing methods listed in post#1, ASTM D2709, Sandy Brae, and HPT, the water test I like best is one not listed: capacitive % saturated meter
Its easier and faster than any of them.

I like the hot pan test much better than the heat/weigh method. We are trying to get the water to below 300-500ppm, which is 0.05%. To use the heat weigh method you need a very accurate scale and a large amount of SVO. If your scale reads to 0.1 gram, it won't measure 500ppm in 100g of SVO. Larger amounts of SVO usually exceed the capacity of the scale. And larger capacity scales usually don't have good resolution. Its also very hard to ensure that you have boiled out all the water from your SVO sample, suspended water is hard to remove by simple boiling, it often is present even after coming directly at 350F from a fryer.
Last edited by SunWizard on Wed Oct 13, 2010 9:09 am, edited 2 times in total.
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Postby John Galt » Sat Mar 29, 2008 9:18 pm

If you want a simple "go - no go" test, the HPT is adequate.
If you want to know how much moisture is present, or test a diesel fuel blend then the WHW is more accurate.
Triple beam balance, 0.1 gm resolution, 200 gm capacity is adequate for the job. One method isn't inherently better than the other; it depends on the application.

Is a fork better than a spoon? Depends on what you're eating.
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Postby David » Sun Mar 30, 2008 4:16 am

I like the hot pan test for its simplicity. I have instilled a measure of consistency to it by using an electric hot plate with a tempostat to heat the oil. It will get the oil well and truly Smoking hot but never hot enough to self ignite. I simply let the oil reach Max temp and test.
I believe it is probably hotter than needed but I see this as adding a measure of accuracy. If there are no bubbles at all at really hot temps, I can be sure the oil is well and truly dry enough.

I also use a pool of oil rather than testing on the pan surface itself. this allows multiple tests of different samples if needed and a reasonable amount of oil to be tested which easily shows any bubbles without cooling off what is in the pan too much.

I believe the quantitative method probably shows more testing margin of error than accuracy when done in the home/ Backyard environment.
When Drying my oil, I can read the hot pan tests pretty well to tell me how long the oil is going to take in my dryer. I can perform multiple tests throughout the drying cycle to let me know how far off I am and have learned from these how wet my oil is as far as bloody wet, average wet nearly dry and dry as a bone.

That is plenty accurate enough for my needs!
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Postby John Galt » Sun Jul 13, 2008 6:12 pm

There is also a quick go--no go test using a spoon and a propane torch to heat the sample of oil. Not as definitive as the HPT but quick.
Last edited by John Galt on Mon Jul 14, 2008 12:32 pm, edited 2 times in total.
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weight, heat, weigh tests

Postby david p » Sun Nov 23, 2008 5:14 pm

i recently got my filter/de-water setup up and running. i'm using something very similar to john galt's upflow system. i tested the oil using the weigh/heat/weigh method. i used a small camping pot and heated the oil on the stove so i didn't have to remove the thermometer (when using the microwave). i heated the oil to 250 degress and held it there for 15 minutes, then weighed. i tried 20 minutes also, but only .1 grams of water was burned off in the extra 5 minutes, so i figured 15 was plenty. i used a triple beam scale with .1g accuracy and 600g capacity. here are my results of 3 seperate tests:

#1
oil = 349.5 g
water = .8 g
% = .23%

#2
oil = 348.6 g
water = 1 g
% = .29%

#3
oil = 351.8 g
water = .7 g
% = .2%

average = .24%

so, based on this result i have about 5 times more oil than the 500 ppm standard. is that correct? i just want to make sure i'm interpretting this correctly.

also, i was wondering about the calculation. the webpage on utah biodiesel that gives directions on how to do the quantitative water test shows the % calculation as water weight divided by wet oil weight. wouldn't it make sense to divide the water weight by the dry oil weight? this makes very little change in the outcome, but i think it's technically correct.
'02 VW Jetta with Elsbett 1 tank system (plan to run on WVO)
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Postby John Galt » Sun Nov 23, 2008 5:24 pm

based on this result i have about 5 times more oil than the 500 ppm standard. is that correct?

That appears to be correct. I would do a confirmation with a HPT since 500ppm is considered the lower limit of the HPT sensitivity.

The webpage is correct. Percents are calculated on total amount. For example, a 100 liter mix of 20 liters VO plus 80 liters ULSD, is 20% VO.
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hpt

Postby david p » Sun Nov 23, 2008 10:16 pm

i tried the hop pot test originally, but i was just not comfortable with interpretting the results. it just seems so subjective. there are definitely some bubbles that come up. but, since i have no previous experience i don't know how many bubbles means exactly what amount of water. i tried looking at the youtube video link you suggested, but the bubbles were hard to see. the problem is the glare off the surface of the oil makes it impossible for the camera to see the bubbles. i even tried filming my test so i could post a link to it on the forum, but again it was too hard to see the bubbles because of the glare.

do you have any suggestions for how to get rid of the water? my current plan is to buy a drum heater and some insulation. then try heating the oil and letting it settle and hoping that gets the water out. currently, the oil is in a metal 55 gallon drum, so i can heat it easily enough.

i've thought about running a small experiment on my stove to see if heating and settling the oil will remove the water from a sample. (heat on low in pot, let settle 12 or so hours, siphon off the top and run the weigh, heat, weigh test) don't know if this will work, but i just thought it might be worthwhile before speding a couple hundred dollars on a heater and insulation. your thoughts?
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Postby SunWizard » Sun Nov 23, 2008 11:29 pm

No bubbles is what you need to try for, I get that on all the VO I burn.
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Postby John Galt » Mon Nov 24, 2008 12:54 am

do you have any suggestions for how to get rid of the water?
Not here. This discussion is on methods to test for water in VO.

Go search for discussions on dewatering. Don't hijack this one.
Last edited by John Galt on Mon Nov 24, 2008 6:29 pm, edited 1 time in total.
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Re: weight, heat, weigh tests

Postby karma » Mon Nov 24, 2008 5:54 pm

david p wrote:plenty. i used a triple beam scale with .1g accuracy and 600g capacity. here are my results of 3 seperate tests:

David,
Well done to follow through and complete a few trials for the WHW test.

I recommend you also do a control test. Take a known dry oil sample (eg 500ml) and weigh it. Then add some water, say 5 ml or about 1% of the total volume, and weigh it again. Shake it up to observe the effect and distribute the water. Then perform the WHW test and compare the result.

What clarity was your oil before the WHW test? Comparing your calculation with the graph in John's post at the top of the thread, your oil should have been cloudy.

If there was any volatile solvents in the oil, they would also evaporate during the WHW test and appear to be water.

As an aside, I did an error calculation with your data.
The average weight loss was 0.24% +/- 0.06 %. The actual weight loss could be as low as 0.18% and as high as 0.30%.
The error in the final calculation is high for 2 reasons. Firstly the weight loss is calculated as the difference between 2 measured weights and this doubles the error for the weight loss. Secondly, the weight loss is small compared to the starting weight The net effect is a +/- error that is large compared to the data.
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Postby dadsdiesel » Mon Jan 26, 2009 7:25 am

First - Thanks for linking my video. It was my first try at a taped instruction video.

I bought a Sandy Brae water tester this past Christmas and have yet to try it!
If I can assemble a few experiments, I will try to post them here, and in the other two major related discussion boards. (I may also try and update HPT video)
One Update - I now use a cast iron Fajita pan to heat the oil. Temp is more even and gives better results.

I agree with Sun Wizzard. Try and acheive NO BUBBLES! I don't think there is any way to place a ppm value on number/size of bubbles with repeatability.
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testing testing

Postby Darren » Mon Nov 23, 2009 5:58 am

I've been trying to test for water in a sample of used cooking oil that has been through a cold upflow system.

I've got a caste iron skillet and heated on a gas hob. I monitor the surface temperature withwhich is 160 C a IR temp gun until it is above 320 F (which is 160 C not the 130 C John stated above) I then stop heating and let the temperature fall to 320 F and then perform a crackle test.

I pour in a small amount of oil from a teaspoon (less than 1/2 a teaspoon) that spreads less than an inch in the pan. I can see no bubbles in this sample.

I then start heating the pan again until this sample starts to smoke (about 370 F measured with IR gun) and then peform a hot pan test. I dump half a cup in which is enough to give about 1/4 inch depth over the pan. This shows some bubbles.

Anyone got any comments on these methods. I've repeated this test a number of times with the same sample and get the same results every time. Wondering about the discrepancy between the two test methods.
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Postby SunWizard » Mon Nov 23, 2009 9:47 am

Try changing only 1 variable at a time, amount of VO or temp. Changing both at once its hard to compare.

1/2 a tsp is more VO than a normal HPT, which uses a thin film of VO smeared with your finger, wait until it smokes. Then the IR temp isn't needed. I think its better to not stop heating, for several reasons, mainly that the temp drops when you pour in the VO and you want it to rise again quickly at a consistent rate.

1/4 cup is what I use, with this amount its easier to see any bubbles compared to 1/2 tsp. This could be the cause of your different results.
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