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Non-Invasive Tank Level Detection

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robski

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Hi all,
I'm looking for some help with a project i am working on. I am looking to design a system to monitor the level in a tank. The tank is metal and approx 1.5 metres X 1 metre and about a metre deep. Its a large fuel tank you would get on a big industrial generator, the type you would hire out.
I am looking for a non-invasive method of detecting the fuel level. I have looked at many methods but am struggling a bit. The difficulty obviously comes because it is required not to break into the tank. I was looking at a way of sweeping a signal through the tank and having a series of detectors to pick it up and depending on the time each recieves it could work out the level??? I also looked at various capacitive and inductive sensors but it would appear they will not be able to sense through the wall of the tank.
Any help with this would be greatly appreciated.
Thanks
Rob :)
 
Can you put the tank on weight sensors? Will give you a very accurate and totally non invasive method to sense it's level.
 
One way of doing this which I have thought of for my farm equipment is put a Tee-peice at the lower fuel outlet and arrange a SS pipe or thick walled plastic pipe to run up the side of the tank. Then encase a strong barrel Neo magnet in epoxy or fiberglass to ride up in the tube. Then put some 1101 hall effect sensors along the height of the tank so as the magnet passes each hall effect it will output a 5 volt pulse. One could even arrange for the lowest hall effect to stop the motor so it doesn't run out of fuel. Depending on the nature of the unit will depend on just how robust it needs to made but this idea can be a cheap easy way to solve the problem.

Cheers Bryan
 
What type of fuel is it? An idea would be to use a method similar to that used on propane tanks. They measure the temperature at various positions from the top to the bottom of the tank.
The propane causes the temperature of the tank to be lower than the empty parts of the tank.
 
Through a thick wall of metal I think that method might be difficult to get any kind of decent results with, regardless of the fuel type, at least with any precision.
 
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Hi all,
Thanks for the relpy's. The weight sensors are an option which would require someone being present when they are delivered to ensure they are put down correctly on them.
Unfortunately breaking into any of the pipe work is not possible because they are hired out and therefore cannot be interfered with.
The temp sensing is interesting although i'm not sure it would work on a diesel tank??
Like you say, getting a reading through the wall of the tank is going to be very difficult, if not impossible. Perhaps i'll need to re think things.
Does anyone know of any other methods or have more info about those discussed??

Thanks
Rob
 
Just been looking at hydrostatic pressure devices. Would it be possible to drop one into the tank to the bottom and measure from there??
It would need to be small enough to fit through the filler cap hole.
Thanks again.
 
You could mount ultrasonic transducers at various levels down the outside of tank. You will a significant echo when liquid is behind the transducer. Its speed will depend on fluid composition. Water will be about 1480 cm/sec. A round tank will partially act as a parabolic reflector returning a strong echo from other side of tank.

No fluid behind transducer point returns insignificant echo.
 
I've had this question before and devoted a lot of thought to it then. I just devoted a little more now. I still can't come up with anything reasonably accurate, if you aren't able to modify the tank at all. Another solution, instead of measuring the level of the tank, you could calculate it. I assume the fuel line coming out f the tank is a small diameter rubber hose (or similar) that you could remove, insert a flowmeter, and reconnect without making any permanent modifications to the the tank or generator. You could simply remove the flowmeter and clamp the hose back onto the tank when you're done. output from the flowmeter could go to a totalizer circuit which could even give you a digital readout scaled for "XX gallons/liters remaining"
 
My original thought was to have a series of some sort of sensor down the outside to pick up the level at different points. If the ultrasonic transducers would work through the metal wall of the tank it would be perfect. Would that be the case? Do you have any idea of exactly which type of ultrasonic transducer to use?

It would also be possible to use some sort of flow meter in one of the fuel lines but i need to have a proper look at the generators. I haven't yet been to look at them but its on my to do list because obviously its difficult to properly assess the situation without knowing exactly the type of generator being used.

To give you an idea as to the scale of generator being used: **broken link removed**

Thanks again :)
 
Just had a quick look at ultrasonic devices and they have ones with transmitter and receiver on same board. Would this work when on the side of the tank or would it be better to have the transmitter on one side and the receiver lined up with it on the other side of the tank? I appreciate it would require a lot of experimentation to get it set up to try and see through the wall, things such as frequency, etc. ( Sorry if i've got this wrong and it wont work, i'm very new to this. :) )
Thanks
 
Ok let me get the info straight.
Is this tank something that you are renting from some one or is it something you are renting out to a customer.

And is the reason you cant make any modifications to the tank is that you will void the warranty of the equipment.

is the fuel fill inlet directly welded onto the tank or is it on the side of the equipment.
What I am getting at is that you can mount a sensor in the cap of the tank if it is directly on the tank.
A picture of the tank would be of great help.
does it have to be an electrical means of sensing the fuel level or just the amount of fuel used.
There are ultra sonic fluid level sensors that you can mount in the fuel cap.
the only problem is that if the cap is not put on securely or all the way on it can skew the readings.
also there will be wear and tear on the connections every time you refuel the tank.
is it a diesel generator or welder or aircompressor.
 
Sorry for the lack of info, i appreciate its difficult to come up with solutions when its not clear exactly whats happening. I haven't been to see the exact generators in question but i'll try to give you as much as i know.
The generators are to be hired out for use on sites such as music festivals. They are large diesel generators.
There is a problem with them running out of fuel because they can be situated up to 1-2 miles apart. Obviously when they run out the vendors like hot dog and burger stands etc, get very upset :( Because they are rented out it means i cnat start chopping into its wiring or anything hence the need to come with something which wont interfere with it.
I'm not sure where the fuel inlet is im afraid.
The measurement does need to be electrical due the requirement to send the information wirelessly back to a hub to monitor it.
I have considered the filler cap as an option. It would be quite easy to come up with something which could replace the filler cap, it would however need to be an exact fit.
I'm not sure if the filler is directly on the top, if it has a spout protruding from the top and whether it is straight or at an angle. Sorry again, i know this doesn't help much.
Thanks again for the help :)
 
Robski I don't thin that you are in the US.
in your country do you have FSR (family service radios) the opperate on a 400mhz range.
if so you can use a Arduino Fio to interface with the fsr radio and a float sensor you can put in the tank via the fuel inlet if it doesn't have strainer or an anti siphon device.
You can program the Arduino Fio to key up the radio and transmit a pulsed code to tell you what gen needs fuel.
and have the system run off it own battery or the starting battery with alligator clips.
these radios in the US have a good 1 to 2 mi range and no licence is needed to operate them.
you can make your own float switch with a mercury switch and a float made from thin aluminum or something that is not reactive to diesel fuel.

I did some research if you are in the UK then the proper radios are the pmr 446mhz radios they sell on ebay from 16 to 50 pounds. and you can get up to 4 mi range.
 
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Here at work we have a oil heating system, I fitted a fuel guage to our outdoor tank.
The tank just has a nylon pipe inside it with a brass weight that holds in on the bottom (pipe goes in from the top breather hole).
In the guage there is a mini air compressor (fits in your hand), it compresses air untill it blows bubbles through the tank at which point the pressure doesnt go up any further, from this the guage tells you how much is in the tank.
The only thing the guage needs to be set up with is the density of the fuel at a known temp.
You could build one of these or buy one, I'll go and look at the manufacturer of the guage if you like.
 
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Thanks very much for that. I appreciate the advice. yes i am in the UK. I looked into the wireless side of things and to be honest, as it is something that i have had very, very little experience of it seemed like a whole seperate task so i was going to handle that seperately.
I looked briefly into the bands i could use that dont require a licence and i got a bit lost. I also had a bit of trouble finding a transmitter/receiver unit that would give me that range so your advice about the Arduino Fio is very usefull, thankyou. Any more knowledge you have on those would be greatly received :)
As i get more and more into it i'm starting to think i'm going to have to go in through the top, possibly using the filler cap or a breather. Again, i'll have to get some more definitive info on the exact generator being hired.
Dr Pepper, if you could get some information about the manafacturer of those gauges that would be great.
Thanks everyone.
 
No probs.
Its a PIUSI instruments, this one is fitted to a 50,000 litre tank, probably a little bigger than yours I presume, the same company do them right down to portable equipment tanks.
Good job I looked, we need some more juice before winter.

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Have you checked if they come with a level indicator of some kind? Sorry for the question but it is quite common for gensets for renting

The level of tanks in CO2 batteries (used in ships) with several tens of tanks is checked by weight or with an ultrasonic system. This last when you do not want to disconnect them from the pipe line.
 
Thanks for that i'll check them out.
I'm not sure if they come with any level indication or not. I would guess they would have some sort of gauge on the side but i'm not sure if it would be possible to use it without causing damage. I also need to get it from a mechanical signal to an electric one which could also prove difficult. :)
 
Most high end generators have alarm outputs to show like low fuel , over crank , over load , ect ect most of the time it is via a RS485 data and some time just dry contacts.
 
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