Testing WVO and biodiesel for water.

[dgs]

Since posting more and reading the posts on the UK forums I have noticed the few (if any) that actually test for water in oil and bio. Even dry washed biodiesel contains around the 600ppm level. The simplest way to get an accurate figure for water is to use the carbide manometer. I have used mine only a few times, the drawback being crushing the carbide is a pain in the backside.

About 18 months ago I purchased a Sandy Brae from Utah Biodiesel, it works really well and is very accurate. Drawbacks, well there are a few. The machine with all the bits and pieces paid is the thick end of £300. Also no way will it give you a result in the 20 mins or so that it states, it's more like 2 hours. The chemical is also very expensive £53 for 25gms. This, however is enough for 50+ tests.

About 1 year ago I picked up a second hand Karl Fischer, brilliant thing. After callibration it will do one test every 2-3mins if the water is low. Drawbacks, price of the solvent and titrant @ £150 for 2x small bottles.

All this is leading up to the fact that some time ago I saw a post on infopop by a guy that calls himself Sun Wizard. The idea is excellent. A cheap capacitive RH sensor linked to a capacitance meter. After trying to get one of the honeywell sensors for the last 18 months (now discontinued) I have now found a UK company that sells an equivalent sensor and am in the process of setting up this simple little system.

Total cost will be around £20-£30  but the meter and sensor can be left set up on the bench, all ready to be lowered into the next sample. This has got to be the most convenient way ever to test for water. I will report how I get on.



   This is Sun Wizards original post.
I am testing a Capacitive water in oil meter I made and its giving very good results so far. I am doing many calibrated samples and tests in the Science project thread which are also useful to test this device. I have compared it very closely to my Sandy Brae tester which is $2 per test, uses hazardous hyrdride so I have to put on gloves, goggles, protective shirt, etc. This meter is much quicker and simpler in every way, dip it in the sample, wait for a stable reading for 30-90 seconds, compare to a chart to get % saturation and PPM water.

It gives results in the same way a $3000 unit like the Eesiflo Online Water in oil Monitor I got a high accuracy (0.5%) capacitance meter ($45) and a honeywell humidity (RH) sensor for $5. Here is a thread with full details, links to parts, how to calibrate: Homebrew capacitive water in oil meter testing The only drawback is that above 100% saturation, it maxes out and reads the same value. Getting below 100% saturated is a very good thing and should be a goal for everyone. Because if you are near saturated, humidity brought in from your tank vent, or a temp. change could mean free water condensing in your tank.
Here is a chart of my 1st data points from it:

This would also be very handy for the Bio folks, so I will post this there too. They don't have to account for the widely varying FFA as we do. I came up with a way to calibrate without a sandy brae tester.

I will be curious to see some others data points. I know some of you will want one of these right away. I wish I made one long ago. If you already have a digital voltmeter that reads capacitance, its only $5 for the humidity sensor to try it!

                     Just click on the graph to enlarge.

[Julian]

That sounds interesting, especially if built into a processor or drying system with a remote readout if it could be done safely.  That could go a long way to automating part of the process.

What is the maximum operating temperature for the sensor?  Stat that, just found the answer for the Honeywell one at least ... it's 120°C ... well within our limits.

As you say HCH-1000-001 is discontinued, but Farnell spookyly offer a Honeywell HCH-1000-002 as an alternative at £3.49 also with a max temp of 120°C.

There's also the HIH-4000 Series, although a little more expensive at £16.10, it's temperature compensated, looks to have a simple voltage output, but only works up to 85°C.

[dgs]

I think I looked at all those Julian, the 002 is 3 pin? from memory but also discontinued. I think all the others work on resistance which I have been informed will not work for our purpose.
The one I have found is from Omni Sensors, It's an HC201.

I have spoken to a few on Infopop since reading Sun Wizards posts (he doesn't seem to post anymore) who have set up similar devices and all seemed to get accurate results with very linear responses.

As you say, one built into the drying system would be very informative.

One very interesting thing about the graph is that the saturation point increases as a result of the FFA %

[Jamesrl]

Hifly, Vince, got hold of some sensors a while ago to connect to a capacitance meter,  I still have the one I bought of him.

If I knew how to build and set up a little moisture test kit I'd have a go at it.

I haven't a clue as to whether Vince actually built one.

[Julian]

Yes you're right, sorry, 002 (although two pin) is also discontinued ... strange they should offer a discontinued item to replace a discontinued item!

The 16 quid HIH-4000 Series has three pins though.

There's a DHT22 capacitive humidity sensor with a built in thermistor that's used quite a lot with Arduino projects, so there'll be loads of code available, it should display on an LCD or PC and works up to 125°C.  It looks a lot more bulky than the alternative you found though.

Any idea why a three pin sensor isn't suitable?



Jim, have you got any info on the sensor ... does it look like this ...

[Bill]

I use one of these, Honeywell HIH-5031-001. I got it from CPC, about £10.  It is a capacitive sensor with a built in circuit to convert to a voltage output. Its a three wire deice and it does require a low voltage input to drive it but its straight forward to use. Read the output with a DMM. Link to tech doc.  http://sensing.honeywell.com/index.php?ci_id=49692
I use it to monitor the humidity of the airspace above the biodiesel when drying to determine the point at which the moisture content decreases no further. At this point the bio is clear.

[Bill]

Just checked and the HIH-4000 is the same as the HIH-5031 with wires instead of smd.

[Chug]

Dave, slightly OT but did you see the guy on infopop posting about removing water with epsom salts?

[Julian]

I use one of these, Honeywell HIH-5031-001. I got it from CPC, about £10.  It is a capacitive sensor with a built in circuit to convert to a voltage output. Its a three wire deice and it does require a low voltage input to drive it but its straight forward to use. Read the output with a DMM. Link to tech doc.  http://sensing.honeywell.com/index.php?ci_id=49692
I use it to monitor the humidity of the airspace above the biodiesel when drying to determine the point at which the moisture content decreases no further. At this point the bio is clear.

Sooo ... what happens if you stick the sensor in the bio?

[Bill]

Never been brave enough to try that and its now hard wired into the control circuit so its not so easy. Had a look at the sensor in its housing and it looks like it has got wet with splashed bio over the course of time. It still works OK, gives sensible readings and its repeatable.
I can feel the urge to get another and experiment. I made a carbide manometer for checking water content but I'm not so sure about the results from it, an electronic device would be better.

[Julian]

Understandable!

One thing that came to mind was the effect of methanol.  I played for some time trying to dewater methanol by various means and none seemed to work.  Silica gel, for example, stank heavily of methanol so I assumed that was being absorbed in place of or even in preference to water.

Assuming you haven't already tried, is it possible to expose your sensor to concentrated methanol fumes ... may be by holding a jar with methanol in the bottom over it to see if the reading alters?

[neisel]

Is all this really necessary or is it just getting a bit anal?

I water wash at a high temp & then dry at a high temp by circulating the BD through a pierced 'L' shaped pipe about 18" length in total with a fan blowing over the top.

After about 2 hours I take a sample, cool it in water for 20 odd minutes & then put it in the freezer until it begins to freeze. I remove it, let it stand until it all becomes liquid (but is still very cold) & do the small print read test. All the time the drying process is continuing so it is drying for at least another 40 minutes after the sample is taken. It always passes. I leave the sample in the fridge overnight & it remains as clear as glass.

I reckon that is in the groove & will do. How much better does it need to be?

[Julian]

Neil .... it's not compulsory!

But I think you've posed a rhetorical question.  I admit I use a lot of guess work when it comes to how dry my oil and bio are, but if I went to the trouble you do I'd be grateful of an instrument that costs relatively little and gives a reasonably accurate reading in a few seconds.

[dgs]

Dave, slightly OT but did you see the guy on infopop posting about removing water with epsom salts?

Yes, I do remember that and I'm pretty sure that IMB tried to replicate the results and it didn't work for him.

[dgs]

I take your point niesel. If you are happy with the way you dry and you have had no problems then I wouldn't try to change your thinking. It's just that over the last couple of years I have had quite a few callers wanting their bio testing for water. One in particular whos sample was really clear was over 1000ppm.

It is very rare that I check someones water that has a nice low level (2-300ppm)

As Julian said, for such a small outlay and the convenience this seems such a good idea.