ok finally made some time to fix/complete my manometer
the first calibration did not work well due to the plastic tube leaking as it passes through my mason jar lid (hot glue gun glue did not hold-up, fixed with plastic epoxy)
adding a large marble when mixing seems to help the reaction (John previously mentioned)
my 2000ppm calibration sent the water so high i thought it was going to come out the top!
here are my calibration water measurements
DRY - 10cm
500ppm - 37cm
2000ppm - 130.8cm (had to break seal on jar to prevent water overflowing out of tube
I'm gonna make a calibration using 1000ppm & maybe 1500ppm sample
i like the sensitive nature of my system
john - any comments please...?
p.s. - i'm starting to burn bio again (B50 in TDI PD) because i'm confident moving forward my bio is real dry (<500ppm)
You probably have too small a headspace in your jar which will result in very high readingS. I would just use a smaller sample size, say 50 gms. This will halve your readings and still be very accurate.
how does that happen? the manometer only measures pressure increase.
Ideal gas law... smaller the headspace the steeper the pressure vs water content curve. Meaning if you calibrate at a certain headspace volume you have to use that volume each and every time
Would using the calcium carbide to dessicate the oil for the calibration work? Say take some new oil and add some crushed calcium carbide then settle it for a few days? I'm thinking it could get the oil drier than heating it up.
I really like that tube mortar idea of yours.
I made a tube mortar using a heavy bolt instead of a piece of steel rod which I didn't have.
I made my tube mortar by taking a 6" long 3/4" diameter black pipe and capped one end.
I used a 24" piece of rebar laying around and use it to pound the carbide. Slipped some plastic tubing over the end of rebar to make comfortable handle.
I used my hand grinder and made the end of rebar round and somewhat pointed.
I use the screw on end cap as a "measuring cup" so I use approx. the same amount each time.
Using calcium carbide to dry biodiesel samples would work. Just keep adding a small amount at a time until the bubbles stop. Do it somewhere very well ventilated.
Maxoil burner, did you try a smaller sample size?
If you're looking for a small amount of crushed carbide to experiment with, you can get it at most hobby stores as Bangsite. It comes in a toothpaste looking tube and it's resealable. I have one of those repro cannons that uses it. Rattles all the neighbors windows. I saw it on ebay too.
1987 MB 300D Turbo
Summer Blend - WVO w/10%ULSD,5% RUG, splash of acetone and gum turp. Afterglow mod,EGR delete, gutted cat.
1999 MB E300 TD - My own 2 tank system. EGR delete
have not tried smaller sample yet, just started a new 40 gal. batch. going to try it on this new batch. thanks to you i finally have a easy way to check water content
I prepared calibration samples for 1000 ppm and dry in one liter jars. The 1000 ppm sample is noticeably turbid, the dry sample is clear and bright. Calibration gives a 31ppm/cm factor which is consistent with the values reported by others. However I was surprised that the BD sample tested didn't become clear. After settling for days there are particles of un-reacted carbide in the bottom but the BD remains only slightly less turbid than the 1000ppm reference. If the carbide is reacting with all the water in the sample then why doesn't the BD sample become clear and bright after the test?
What have others observed?
Calibration reference samples: Dry BD and 1000 ppm [1ml H2O per liter BD]
So your fail point (500ppm) is 16cm, which is a good readable scale and not far from my calibration. The unreacted carbide will settle to the bottom but some the reacted carbide ( calcium hydroxide) will remain in suspension for a long time, in fact it would take a centrifuge to remove it completely.
Going back to a question asked by Rickdatech, can you dry the samples using calcium carbide? I replied yes without thinking it through properly.
You could dry a sample of biodiesel to virtually zero using carbide but only by adding more carbide than was actually needed. The extra carbide would react the instant you added the reference amounts of water
Recently recalibrated using 50 grams of each sample (dry-500ppm-2000ppm), much better results because the 2000ppm sample stayed in the tube!
I'm drying down to approx. 250ppm weather permitting & using the bio as I produce it...not sitting around for more than a couple of weeks.
How about another method.
New oil from the store. Test as is then make a sample that is +2000ppm (1ml to 500ml). Test the second sample. Plot them on graph paper with cm of reading on the left and ppm across the bottom. Draw a line between them. Move the line left or right so it crosses the line at 0cm = 0ppm.
Just trying to simplify the calibration a little.
I think 250 is a good figure to aim at, although 500 is permitted it really is too high. Drying much below 250 can take a lot of time and energy. I did an experiment last Autumn ( fall ), I left biodiesel in an open topped container and retested it every week. On average it absorbed 50ppm per week, but properly stored it should remain dry.
I like your simplified calibration method, Rickdatech. I would make a couple of suggestions, first it might be better to use dino diesel rather than veg oil as veg oil can be very slow to give a full reading.White spirit,kerosene would do as well. You need to make it clear that the first reading is plotted with the ppm at zero, and it might be simpler to say "draw a parallel line to the first line passing through the zero point" rather than move the line to the left or right.
The 500 ppm reference solution was always difficult with a syringe
I changed the jar on my carbide manometer this week so I thought I have a go at calibrating it using Rickdatech's method. I tried to use kerosene but it did not work. My kerosene is so hydrophobic that even after a minute of vigourous shaking the water dropped out almost as fast as I could pour out the sample. So forget my suggestion to use kerosene or white spirit.
I used new rapeseed oil ( canola) this time and got an initial reading of 18cms. I added 1ml of water to 500ml of the oil and shook it vigourously for a couple of minutes. When tested this sample read 120cms. I plotted the graph and drew the parallel line through the zero point.
My fail point (500ppm) is now 27cms so its just as well I did recalibrate.
just a couple of points to look out for...
If the 2000 ppm sample gives a very large reading as mine did and your manometer tube is too short, use a 50gm sample and multiply the result by 2.
Veg oil can take 15 minutes or more to stop at a final reading, dont rush it.
Hold the jar by the cap to avoid warming the sample as you shake and dont shake so hard that oil gets into the tube.
Thank you Rickdatech, your method is excellent and simplifies the calibration of the carbide manometer. If you want to change the text on make-biodiesel.org please do.
Rather than cutting the sample size, how about cutting the reference back to 1000 ppm?
How about these instructions:
To calibrate the carbide manometer, you will need a bottle of new store bought vegetable oil.
1. Test a sample of the oil straight from the bottle and record this reading.
2. Prepare a 2000 ppm sample by adding 1 ml of water to 500 ml of oil and mix thoroughly.
3. Test a sample of the 2000 ppm oil and record the reading
4. Plot the two recordings on a graph with ppm marked along the bottom and cm along the left side of the page.
5. Draw a line between the two points.
6. Draw a line parallel to the line above that crosses the 0cm, 0ppm point on the graph.
7. Erase the line you drew in step 5 above.
If the 2000 ppm sample creates too much pressure for the manometer to read, then you need to start over using a 50g sample. You will need to always use a 50g sample size or your calibration will no longer be valid.
When you buy oil at the store, it has some water in it. In this test we ignore that initial water in the beginning of the calibration. When we draw the parallel line, we are adjusting for the fact that the purchased oil has water in it. The advantage of this method of calibration is that we no longer need to “dry” our calibration oil.
When performing the calibration, make sure all the tests are performed at the same temperature. Room temperature (68F) is best.
edit - changed sample size from 1000 ppm to 2000 ppm
edit - changed the note about sample size to emphasize that if one changes sample size, then all calibration tests AND subsequent tests need to be performed with the new sample size.This message has been edited. Last edited by: RickDaTech,
I found it easy to dry 2 liters of BD, then add 1ml to one liter for 1000ppm, and finally mix 300ml of each to make the 500ppm sample. The 1000ppm tested at 31.0 to 31.4 cm and the 500ppm at 15.4 to 15.8 cm, for a calibration constant of 32ppm/cm.
The manometer tube is attached to the meter stick with 1" binder clips,
masking tape was placed on the meter stick and the calibration levels marked on the tape.
The manometer assembly hangs from a hook and the 500 ppm calibration marks are a convenient go/no-go reference. A short piece of 6mm OD tube is sealed into the jar lid so the manometer is easily connected/disconnected.
I found the most important point for consistent results was to pulverize the carbide to a very fine powder.
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