I just released an article in my latest newsletter, Biodiesel Review, ( http://www.biodieselreview.com ) on all the different ASTM tests that make up the full ASTM D6751-08 panel and a brief summary of what they test for and in some cases how the test is done.
Click Here To See The Article.
I figured some of you might be interested in what I found & wrote about.
For those with more experience with the tests, feel free to chime in & give more details on them or correct any errors that I may have.
Also, Bently Biofuels has an excellent write-up of the different tests performed as well and what they may indicate. http://www.biodieseltesting.com/tests.php
(Also, new in this post, I'm including the Home Brew Equivalent (HBE) tests that I'm aware of.
If I don't list one, it means that I'm not aware of an equivalent test. If you know of one, chime in & I'll add it to this first post.)
ASTM D6751-08 Tests
ASTM D6584-Total & Free Glycerin Total 0.24% Free 0.02%
This test is by far the most important one. It's a measurement of how much glycerin is left in the finished product. Too much glycerin indicates the reaction didn't go well or that the fuel wasn't properly washed.
HBE - 3/27 Biodiesel Conversion Test
ASTM D445-Viscosity @ 40 deg. C Limit 1.9-6.0 cst
This is an indicator of how viscous the Biodiesel is. If it's too thick it won't flow right in the fuel system. It's very rare that Biodiesel ever fails this test. If it does, it's usually an indication that there's still a lot of oil in the fuel or some other contaminant.
HBE - World Famous Dr Pepper Viscosimeter
ASDM D664-Acid Number Limit 0.50 mg KOH/gm
This indicates how acidic the fuel is (similar to what a titration measures, only much more accurate). If fuel is acidic it's an indication of high free fatty acid levels or other acidic contaminants still present in the fuel. Highly acidic fuel can corrode fuel injection components.
HBE - Titration testing, to a point
ASTM D1160-Distillation Temperature Limit 360 Deg F Max
This is a test that measures what components "boil off" as a sample is heated. Biodiesel has a known boiling point. If during distillation the sample exceeds that point excessively, it's a good indication that there may still be oil in the sample. If it all distills off too low, then other contaminants may also be present.
ASTM D613 Cetane Number - 47 Minimum
This test relates to how well the sample will ignite. Biodiesel purposely put this number higher than diesel in the specification to brag about how good Biodiesel is. It's extremely rare that this test fails, if it does, it means your sample probably isn't Biodiesel or has high levels of contaminants in it.
ASTM D2500 - Report To Customer - No Limit
This indicates at what temperature a sample of Biodiesel clouds up. It gives an indication of when Biodiesel will begin to gel. Granted, clouding & gelling are two different things, but this test will give you a good ball park figure.
HBE - Shove it in the fridge w/ a thermometer & record the temperature at which it clouds.
ASTM D93 - Flash Point Limit 93 Deg C Minimum
This test indicates at what point a sample of Biodiesel will ignite in the presence of a flame as the temperature of the sample is raised. If it ignites before 93 Degrees Celcius (approx. 200 Deg. F), it indicates the presence of a highly combustible material in the fuel (usually methanol). This also impacts how the Biodiesel may be shipped. If its flash point is too low, the transport vehicle must be marked as flammable and hazardous. If this test is failed, it usually means you haven't removed all the methanol from the Biodiesel (ie. The Biodiesel wasn't properly washed all the way).
HBE - Carefully raise the temperature of Biodiesel in a pan OUTSIDE. Introduce a small flame to the top of the heating Biodiesel. Measure at what temperature the flame ignites the fumes from the Biodiesel.
ASTM D5453 - Sulfur Content - S15 - <=15PPM, S500 - <=500 PPM
This test is looking for the presence of sulfur in Biodiesel. Onroad Biodiesel can only have 15 parts per million (0.0015%) of sulfur. Biodiesel for off-road use can only have up to 500 parts per million (0.05%). This is a mandate by the EPA. Fail this test and you can't sell the Biodiesel in the US. This also applies to diesel fuel too. It's rare for Biodiesel to fail this test unless there are contaminants in the fuel.
ASTM D4951 - Phosphorus <= 0.001% , Sodium & Potassium <=0.005%, Calcium & Magnesium <=0.005%
This one is actually 3 tests combined and is done by spectrochemical analysis. The limits for Calcium & Magnesium combined are a max of 5 ppm, Sodium & Potassium have a max of 5 ppm. Phosphorus is 1 ppm. If you fail this test it's an indication that the fuel wasn't properly washed. It's also a good indication that there's still soap in the fuel too. I've seen some customers fail this simply because the water they were using to wash with had some of these components in it. This is also the test that is extrapolated out to identify the 41 PPM limit of soap in NaOH reacted Biodiesel and 66 PPM limit of soap in KOH reacted Biodiesel when testing fuel for soap content.
HBE - Soap testing to a certain extent
ASTM D2709 - Sediment & Water - Max 500 PPM (0.05%)
This indicates the presence of free water and sediment in Biodiesel. The test is performed by spinning a sample of Biodiesel in a centrifuge at high speed. Water obviously will cause problems in fuel systems and sediment can plug filters and leave deposits. There some speculation that this test may be removed in the near future for ASTM D6304, which is Water Testing by Karl Fisher because the Karl Fisher is a more accurate representation of all water in the fuel. If you fail this test, you most likely haven't dried or filtered your fuel enough.
HBE - Hot Pan Test
HBE - Heat, Weigh, Heat
HBE - Sandy Brae Water Tester
ASTM D874 - Sulfated Ash - Max of 200 PPM (0.02%)
In this test a sample of fuel is burned and the ash residue is measured. If the ash levels are too high (ie. sulfated ash) then the sample fails. It's usually an indication that there are contaminants in the fuel since Biodiesel will burn completely.
ASTM D4530 - Carbon Residue - Max 500 PPM (0.05%)
Carbon residue in fuel can lead to carbon deposits in the engine. Too much can cause engine problems down the road.
ASTM D130 - Copper Strip Corrosion Rating - #3 Maximum
This tests the corrosive nature of the Biodiesel sample. If it's too high, then it can corrode internal engine components. It usually indicates contaminants in the fuel.
EN14112 - Oxidation Stability - 3 Hours Minimum
The fuel is tested to see how quickly it oxidizes. If it oxidizes too quickly this means the fuel can go bad too fast while in storage. Several variables will impact this measure such as the type of oil that's used, however there are several additives on the market that can help improve oxidative stability. Even adding Vitamin E to Biodiesel in small amounts can help.
ASTM D6217 - Cold Soak Filter Ability Max 360 or 200 seconds
The fuel sample is chilled to a certain temperature, then brought back up to ambient room temperature. The fuel is then passed through a small micron screen. The time the fuel takes to pass through the screen is then measured. This measurement indicates how well the fuel will do in cold weather at gelling up. The standard is 360 seconds for fuel used in temperatures -12 Deg Celcius (about 10 Deg. F) and above. It should take less than 200 seconds for fuel that will be used in temperatures below -12 Deg C.
There's an excellent description of how this test is performed here:
HBE - Get an equivalent vial and filter screen & cool your Bio down, heat back up & pour through a filter & measure how long it takes. This message has been edited. Last edited by: Graydon Blair,
That cold soak filter test is incorrect!
It specs a 21 psi vacuum for the test. A complete vacuum is around 15 psi(29.92 in/hg at sea level).
They probably meant 21 in/hg vacuum.
He just fixed it.
For the D93, you need to heat up the biodiesel while covered. It's a closed cup flash point test. Also, subsections of D93 stipulate to for 'alcohol control' you need either less than 0.2% methanol or else a flash point above 130 Celsius. So for a homebrewer's test, one should be testing at 130C, not 93C.
Senior Mechanical Engineer
Springboard Biodiesel, LLC
Keep em coming everyone..
I know it may be stating the obvious but the flashpoint test should be done on a SMALL sample only not on any large quantities and certainly no where near the main batch or stores of methanol etc.
If you do happen to have a low flash point due to residual methanol and you try the closed cup test you may lose more than your eyebrows especially if you are trying to test a large sample. 50 to 100ml would be more than sufficient for a homebrewer to see the flash point, you should be able to get away with a lot less.
A quick search of closed cup flashpoint equipment shows a 2-4ml sample size.
That is right for a controlled sample with a controlled flame size in a piece of laboratory equipment. However if you are just trying it in a cup with a lid on then opening it to stick a lighted match or similar in then you typically need a bit more of a sample. It is not always that easy to see the flashpoint of a tiny sample in nything other than ideal conditions.
Hi Graydon Blair,
Thank you for the informations on collective test methods for biodiesel... I have read the link on World famous Dr Pepper Viscosimeter, but it would be more helpful if there is pictorial representation of constructing it... Have you got any info on this Dr Pepper Viscosimeter
I personally don't have anything picture wise on it.
You may poke around on the forum thread where I've linked back to though.
Someone may have done pictures of how it works in the past.
Just curious if anyone has run across additional home-brew equivalent tests for any of the ASTM tests above that haven't been covered.
I may be able to add to your list.
The carbide manometer is a useful alternative way to measure water content. Essentially it works in the same way as the Sandy Brae but can be improvised by the homebrewer,
The falling ball viscometer can easily be constructed from standard plumbing fittings as is shown in my utube video. The formula that I used to translate the readings into Centistokes turned out to be wrong but the viscometer is still useful as a way of comparing viscosities of different liquid. Incidentally if anyone could help with the formula I would be very grateful.
The copperstrip test can easily be replicated . A small heated bath of biodiesel, controlled by a cheap PID controller with polished strips of copper suspended in it for the required time. However its hardly worth the trouble as Ive never had biodiesel that fails.
I test for flash point in an open cup which I realize is technically wrong but can be done. If you practice doing the test with fuel of a known flashpoint such as kerosene FP38°C you can get a decently accurate result.
In this test I wrongly state the flashpoint at 40°C, it actually occurred at 35°C. This result is only 3°C off the flash point of kerosene at 38°C.This message has been edited. Last edited by: imakebiodiesel,
I can offer a possible test for residual glycerol. I dry wash my biodiesel using my own system and like most drywash methods glycerol is not removed as effectively as with water washing. So my biodiesel can be as low as 20ppm of soap and still contain a significant amount of glycerol.
If I test the bio with the Wash Test I get clear separation of the 2 layers inside 15 minutes but a trace of cloudiness in the water layer. This indicates to me the the soap is sufficiently low but there is some residual glycerol. If I retest after a days settling the test will show perfectly clear water in the lower layer indicating that the glycerol has settled out.
Rereading this I should make clear that I confirmed that the soap levels in both tests were 20ppm measured by the soap titration test so the soap levels remained the same but something else changed, methinks glycerol.This message has been edited. Last edited by: imakebiodiesel,
Thanks for the updates!
dang I hadn't been here in quite some time. I guess i'm outdated now. Good news is my Appleseed processor has been working fine for nearly a decade
Home of the biodiesel drinking bears.
2005 Jeep Liberty, 2003 VW Jetta TDI
1992 Dodge Dually Cummins Peirce Arrow Dumpbed
Good to see you!
All the Isuzu's still running well?
I performed a 50/50 shake up test yesterday on some high conversion biodiesel which was <10ppm soap.I also knew this sample contained a small amount of glycerol.
I can confirm the water phase is cloudy when glycerol is present.
This test is probably more useful for those who don't water wash.especially if an Ion Exchange media is used. These resins will reduce soap levels but not reduce any glycerol present.
how can you know that glycerol was present? with a soap test of less than 10ppm the biodiesl to me is top notch. I suspect your soap test is in error or there is a higher amount of mono or di glycerides in the biodiesel which would account for the cloudy shake em up test. Is the liquid in the 3/27 test clear?
" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
No, there would not be any excess of Di's or Mono's in there.
I know what it was as it happened doing one of my experiments.
I will explain.
As I've mentioned before I use "spent glycerol" to de-soap my bio. A friend who also uses this method managed to have a totally clear 50/50 shake up test simply by settling (several days) then heating and bubbling,without water washing.
I thought I would try this (after all if it would dispence with the water washing stage that would be good) but it didn't work for me,I don't think I left it to settle for long enough.
I took a sample before I water washed it and sure enough next morning there was a residue of glycerol on the bottom of the container.
Thanks Tom and thanks for the PM's,appreciate it.
Can you explain "spent glycerol" for me. Byproduct is loaded with soap it works as a degreaser as is so I am having a problem understanding how this product which settles out of the biodiesel can now be used to remove soap from the same biodiesel. Sorry Dave I must have missed something. Keep up the good work!
" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
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