To use the carbide manometer, place the plastic cup on a digital kitchen scales and pour in precisely 100 grams of biodiesel. Using a hammer break up a small stone of calcium carbide and crush it into powder. Fill a plastic drinks bottle cap with the powder and gently place it in the cup of biodiesel. Without delay screw on the cap and mark the level of the righthand side of the manometer.
Hold the cup by the cap to avoid heating the biodiesel with your hand and shake gently for 5 minutes or until there is no measurable movement for a minute. Now measure the increase in the level of the manometer in millimeters.
With my manometer a measurement of 150-180 mm indicates that my biodiesel is dry to ASTM specifications but to be truly accurate you should calibrate your manometer as described in a previous post. Your plastic cup may be a different size and give a completely different reading to mine.
What about the amount of the carbide, should it be the same weight each test?
Yes, the capful of carbide is enough to react with several grams of water so there is no need to add more for the larger 100 gm sample of biodiesel.
Sorry Raften I misread you question, there is no need to weigh the carbide as you have at least 10 times more carbide in a capful than is needed to complete the reaction.
Imake, How do you know that 100% of the water has been reacted with the calcium carbide? Have you done a vapor test on the "spent reacted" sample?
I havent done any tests on the spent reacted sample, in truth I just assumed that all the water would react with the carbide. The reaction is so fast and vigorous that I cant imagine there would be any water left, but I will check. Thanks for the idea.
The carbide manometer can also be used to measure the water content of wvo. Typical wvo will contain a lot more water than biodiesel so it is necessary to adjust the measurement. One option is to make a manometer 50 feet high but I dont think thats practical for most people.
The other more sensible option is to mix a small amount of wvo with a larger proportion of a dry solvent. White spirit, kerosene or biodiesel will do as long as it is perfectly dry.
20grams of wvo/ 80 gms of solvent would be a good start. Multiply your reading by 5 to obtain the correct calibrated reading.
If thats still too much water try 10gms wvo/90gms solvent and multiply the result by 10
I wonder if a 0-15 psi pressure gauge will work with WVO?
`The problem with wvo is there is a wide range of water content possible. I measured 2 different samples today and got results of 1500ppm ( my normal source of good clean oil) and 5200ppm (some old smelly stuff with a layer of water in the bottom of the container.). A pressure guage probably would not show any reading on the drier sample.
Taking things a bit further it should be possible to measure the water content in methanol with the carbide manometer. There might be as much as 5% water in methanol so I will try mixing 10gms of methanol with 90 gms of dry solvent and multiplying the result by 10.
I had a go at measuring the water content of methanol today. I mixed 20gms of methanol with 80 gms of dry White spirit. I added the capful of carbide and mixed. I got an immediate rise of 150mm and then over a 10 minute period a total rise of 750mm. I multiplied the result by 5 to get a true reading of 3750mm. From my calibrated scale that gives a reading of 12050 parts ppm or 1.2% water. I contacted my supplier and he was only able to say the his supplies are guaranteed to be "better than 98% purity." So my reading is in the right ball park.
I have some reservations about this test, Its possible that a capful of carbide is not enough to react all the water in a sample of this size. Also at a reading of 750 the coloured water is right down to the bend at the bottom of the manometer.
I might repeat this test with 10gms of methanol and 90 gms of solvent. This would effectively double the amount of carbide available for reacting as well as making the reading scale more manageable.
I finished washing a batch of biodiesel today and will try an improved drying routine. This time I have heated the bio up to 60degrees C before beginning to blow dry. I shall blow dry for four hours and take a test sample every hour. Ill test the samples tomorrow when they have cooled.
I tested my samples from the improved drying routine and the results are spectacular. The biodiesel was fully washed and then heated to 60 degrees C. The sample I took at that point was cloudy suggesting a high water content. When tested it read 3200ppm.
After an hour of blow drying the sample looked very clear but I know better than to judge by clarity. The sample tested at 300ppm! I was so shocked at this reading I did it again and got the same reading. I was still suspicious so I tested my 2000ppm reference sample and got a perfect reading, the manometer was working correctly.
I tested the sample taken after 2 hours and it read 145 ppm.
Just to remind you of my previous drying routine I used to blow dry washed biodiesel at 25 degrees C and when tested I found that it was taking 7 to 8 hours to dry the fuel to below 500ppm.
With the new routine of heating the biodiesel to 60 degrees it only took one hour to blow dry to below 500ppm.
Note that simply heating the fuel had almost no effect on the water content.
From my point of view the carbide manometer has proved to be a valuable tool. It has enabled me to make my drying routine both more effective and more energy efficient.
It will also allow me to make regular checks on an important aspect of fuel quality.
i told you so
If it’s not broken don’t fix it if you do you’ll break it.
The black dog can be beaten
Yes Copper, I have to admit , you did. In fact it was you who got me started investigating water content in fuel. Next time you call in bring some samples of your own biodiesel and Ill test them for you.
Raften , Im having trouble answering your pm so I going to post my reply here.
From your description of your drying system it would seem that after heating the biodiesel you blow dry with cold air, how long does that take? I use a hot air gun that consumes 1600 watts per hour and Id be glad to dump that and use cold air. Also you describe the fan as a muffin fan, what is that?
The container I use for my mixing vessel is a screw top cup of the sort kids take juice to school in. Here they are really common and cheap. There is another type for sale which is a square cup with a lid that has four lugs that you press down to seal the lid. I didnt go for that type because it has a rubber seal which might not last long in contact with biodiesel but otherwise it should work ok.
Over here they are called Nalgene bottles. They are made from Lexan (Polycarbonate). A canning jar should also work well.
I had a look for Nalgene bottles on Wikipedia, They are close to what I use but the cap seems too small. The one I use is just a plastic cup with a screw on lid. I chose plastic because I was concerned about producing pressure inside a glass jar. In fact the pressure is so low and the gas can always push its way out through the tube so a glass jar with an airtight screw on lid would be fine.
Nalgene bottles comes in different mouths. You want a wide mouth such as this one:
Yes that one looks more suitable. The sort of thing made by Tupperware or Rubbermaid would work. Even what we in Ireland would call a jam jar would be ok. Jam = Jello in US.
What is the availability of calcum carbide where you live?
In response to IMake's question about finding calcium carbide, not much luck in the SF Bay Area but I am still looking. I recently threw out some 20 year old stuff and am second guessing that decision now. Most likely it was not good anyway.
If this was not so expensive to ship (from Belgium?) I'd buy it. Calcium carbide used to be dirt cheap when Carbide lamps was used.
How many test will 1 oz give ya?
Here's 1 oz for $8
An oz wont last long, 2 or 3 tests at most. There are a couple of possible other sources if you cant find it in stone form.
Caving supplies, although led lighting has mostly taken over from carbide lamps, caving supply shops and sites still stock carbide.
Building inspection and surveyor supplies. Carbide is used for testing moisture content in masonry samples in a tester similar to the Sandy Brae tester.
Foundry supplies. Green sand used for metal casting is tested for moisture using carbide.
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