Propane volume detection

Pretty much just getting into this programming ,tried several programs and was able to recreate,that being said, copy someone else project is not really programming. Taking some lessons and decided I wanted to attempt a new project.Sorry for all that but just trying to let you know where I am at in this Arduino learning.

So here is what I would like to attempt,I have a buried 500 gallon propane tank the I obviously can get to the level meters.When it is to filled capacity (80%), it is approximately 400 liquid gallons ,at least that is the way I read it,so 10%=50 gallons and so forth. Is it possible to safely remotely monitor this tank , possibly using something like an ESP8266 ? Tank is around 30' from house and monitor area that I would like to read the value from is not more that 75 feet away.

What I currently own :
Buried 500 gallon propane tank
2 Arduino uno
hand full of components, resistors and such
ESP 8266
Raspberry Pi r3
Thanks for taking the time to read this.

One key part seems to miss: some sensor that tells you how much propane is in that tank.

When you got that, just connect it to your ESP (at a safe location in relation to your tank, with sufficient power supply & water proofing etc), and you can call up your current tank status over WiFi.

Yes sir , I do understand that ,I don't have a clue as to how i would be able to monitor the tank volume ,thought of just viewing it from a camera but that is not really what I want to do. I know that or heard that some propane suppliers have a way to read that value and wirelessly transmit it back to their station so they know that the tank level is low.I worked at a company that also did that for their oxygen tank supply that was being used for manufacturing but other than the fact they used a solar cell and some other transmit device is all I know. Thanks again for your thoughts .

Also considered attaching a 5 volt pressure sensor to the supply line and reading it's value and somehow sending its analog voltage reading through a wireless device(ESP8266). Kinda of like reading water flow from a device similar to a YF-85 water flow sensor.

That is an interesting question. If the tank only contained propane gas then reading the pressure in the tank would tell you how much propane was left. However if the tank contains propane both as a liquid and as a gas I am not sure what happens. My guess would be that the pressure in the tank remains constant as long as some liquid propane remains in the tank.

How are you charged for the propane? Presumably either the tank or the truck delivering the propane has some kind of flowmeter that measures the volume of liquid delivered?

You said you could use a camera. The camera must be looking at some kind of meter, what is the range of the meter and what units does it display?

I obviously can get to the level meters.

Are those mechanical? Of course, you'll need an electrical signal. You might want to do some research... Maybe ask your propane supplier how it's normally done.

I've seen it done by weight (for a small BBQ tank) but that won't work underground.

When you buy propane they measure the liquid flow (gallons in the U.S.), just like when you buy gasoline.

It could be done ultrasonically (measuring the distance to the top of the liquid) but anything inside the tank would have to be installed professionally or done "at your own risk".

Also considered attaching a 5 volt pressure sensor to the supply line

As far as I know, that won't work very well. There is a certain amount of pressure to liquefy it, and that pressure is constant (as long as temperature is constant). As it gets used-up, there is more in gas-state and less in liquid state because the liquid evaporates inside the tank until vaporization pressure is reached, holding constant pressure.

I believe there are only two ways to ascertain the contents.

  1. weigh the tank - not such a great idea in your case

  2. have a float inside the tank that reads the liquid height - hence reply #1

I would imagine a tank that size would either already have connections for remote reading on the existing level meter, or at least have a remote reader that can be installed in replacement.

Once that is sorted, the ESP8266 should be all you need

Using a camera seems downright silly, and measuring the flow out isn't much better.

I would imagine a tank that size would either already have connections for remote reading on the existing level meter,

Does the tank really have a level meter, it does not seem likely to me. I think we need to know how the OP knows manually what is in his tank, and how the person filling his tank know it is full and how much was put in. That will gives clues on how to remotely read the contents.

Small tanks can be weighed which, as has been mentioned, is obviously out of the question here. Another trick used with small tanks is that the part of the tank with liquid in it conducts heat away faster than the part with gas. Potentially that lets you extrenally measure the liquid level, but I am not sure what sensor you could use and since the tank is buried it may not be practical.

1/ Measuring the pressure would give you a good idea of the temperature, but no idea as to the volume of liquid in the tank.

2/ You must already have a pipe from the tank to the house, so why not just run a piece of wire along with it?

3/ Weighing is an obvious mmethod, but probably not practical.

/4 I think that some tanks have an internal float rather like a car petrol tank, with a mechanical gauge sealed to the tank. If yours has, some method of converting that into an electrical signal could be arranged.

Allan

ardly:
Does the tank really have a level meter, it does not seem likely to me. I think we need to know how the OP knows manually what is in his tank, and how the person filling his tank know it is full and how much was put in. That will gives clues on how to remotely read the contents.

The OP says he can get to the level meters, which is as obvious as he says it is, and even implies there is more than one. I submit that the person filling the tank knows the tank is full when the filler stops filling it. He also knows how much went in by reading the flow meter on the filler. I can't see how either of those gives any clue on how to remotely read the contents.

allanhurst:
1/ Measuring the pressure would give you a good idea of the temperature, but no idea as to the volume of liquid in the tank.

I don't think that is quite right. There are are level gauges that work on pressure but I think they tell you you either have heaps or virtually nothing. I believe the same sort of thing is used for automatic changeover valves.

The pressure will only tell you whether there is liquid left in the tank. Propane has a boiling point of -42C at 1 atm pressure, but can be liquified by pressure alone if above it's critical temperature (-187C).

At 20C this pressure is about 150 psi and will remain constant however much liquid propane there is.

If all the liquid has gone and you have only gas left, it's pressure will be governed by the general gas law -

PV = nRT.

and will quickly drop as gas is consumed. That's how the auto-changeover valves work.

Allan

I obviously can get to the level meters.When it is to filled capacity (80%), it is approximately 400 liquid gallons ,at least that is the way I read it,so 10%=50 gallons and so forth.

Most likely, your tank has a float connected to a gauge as shown in the image below. Perhaps you can replace the gauge with a version containing an electronic sensor, or modify the gauge mechanism itself to detect the pointer position.

Got it, I know how it works;

The tank itself does have a float inside it. The float rotates a wheel which, via a magnet, causes an external gauge to display the approximate percentage of propane in the tank.

When your tank gets to about 30% you call your supplier who fills the tank to 80%. The tank gauge gives the delivery truck driver a rough idea of how much propane he can supply based on the tank size. The truck has a flowmeter that accurately measures the volume of liquid gas supplied, and that is used for billing.

So to remotely read the rough percentage fullness of the tank you would need to remove the existing gauge and fit something that can determine the position of the magnet inside the tank.

This product flashes a light when the tank is getting empty. Possibly it could be modifed to use WiFi and give a remote reading it depends how it senses the magnet position.
https://www.youtube.com/watch?v=EfB_MaIB_Tk

Warning : I think most tank gauges use a magnetic system like this where the gauge does not actually penetrate the tank. Howeve in reasearching this I have discovered a method in use where the level is determined by moving a lever and seeing if gas or liquid is dischaged through a vent. Before tinkering with a gauge make absolutely sure it is completely external to the tank and does not penetrate it.

If there's a moving magnet, perhaps a linear Hall sensor could be used? Rather like the throttle on electric bikes....

Allan

ardly:
https://www.youtube.com/watch?v=EfB_MaIB_Tk

The forum screwed up the URL. Here it is fixed:

However, I think you posted the wrong link because that's just an explanation of how you need to thump the gauge to get a good reading (I guess some part of the system can be a little sticky). So that might be something to consider for this project anyway.

@Larryfos what is your application for this? Do you just need an alert when the tank reaches a certain volume or do you need to know the current volume at all times?

I don't know how feasible/expensive it is to replace the current gauge with a digital one that has output that can easily be read by the Arduino. Of course that would be the best solution but I'm thinking of ways you could get a reading from the current gauge. The simplest would be an IR reflectance sensor. When the needle of the gauge reaches the sensor location the reflectance value should change so you could get an alert when the gauge reaches that point. It's possible the clear cover on the gauge is IR opaque so you'd need to do a test but those IR reflectance sensor modules are super cheap.

You could also use a Raspberry Pi with a camera on the gauge then do CV processing to interpret the volume from the needle position in the captured image. I would tend to look for a more simple solution before resorting to that. It will certainly entail much higher power consumption than other options but you may be able to sleep the Pi and only do occasional or on-demand readings.

pert:
The forum screwed up the URL. Here it is fixed:
https://www.youtube.com/watch?v=EfB_MaIB_Tk
However, I think you posted the wrong link because that's just an explanation of how you need to thump the gauge

Just some silly old fart with a hammer, but nearby is a guy who actually knows what he is doing
https://www.youtube.com/watch?v=XeCplibHX_8 and installs a remote reader as described in reply #6. He mentions that there are several different types of dials and sizes. And there will be several different types of reader - including ones that read the whole range. I see there are already phone, wifi and bluetooth systems - all using the remote reader in the above link.

That replacement gauge almost looks like its only purpose is to provide a mount for the sensor and a dial that is not visually obscured by the sensor. So that seems promising for DIY. The question is what the sensor is. I think allanhurst might be on the right track with sensing a magnetic field.

I wonder whether the person filling the tank uses the gauge? If so they would not like it if you covered it up but it should be possible to make something that can be easily removed before they show up to fill the tank.

pert:
That replacement gauge almost looks like its only purpose is to provide a mount for the sensor and a dial that is not visually obscured by the sensor. So that seems promising for DIY. The question is what the sensor is. I think allanhurst might be on the right track with sensing a magnetic field.

I don't think he is. The device looks exactly the same as those on a water meter, which are optical. The whole-range readers read the magnet on the gas side concentric with the dial magnet (if there is a dial).

I wonder whether the person filling the tank uses the gauge?

Surely not. As I said, you just fill it until it stops filling, and/or read the kosher flow meter on the pump - rather than some vague percentage on a tank gauge that may have been attacked by a clown with a hammer..

Sorry for messing up the links. The one that Nick_Pyner posted is actually the one I meant to send. However the video of the old guy with the hammer is also useful. He demonstrates that the gas dial is free spinning using a hand held magnet. His comments about banging the tank might also be relevant, maybe it is only his tank but perhaps the float mechanisms are prone to sticking.

Regarding using the gauge to fill the tank I think it is used. To allow for expansion the tanks are only ever filled to 80% so the truck driver cannot just fill it until it stops filling. The gauge reading does not need to be very accurate. After filling the tank might actually be say 75% or 85% full it does not really matter as the customer will be billed by the accurate flow meter on the truck.

So, what sensor could be used to detect the orientation of the rotating bar magnet in the tank?