Petrol/Gasoline detector for a 12v fuel pump. - Page 1
Forum section: electronics / projects

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: February 26, 2016, 07:56:27 am
content: Instead of siphoning the contents of two 25L portable fuel tanks into a inbuilt tank in a boat that's hard reach with an ordinary fuel dispenser, I'd like to run a small 12v fuel pump to do this.Would like to have a sensor near the end of the rubber hose feeding the tank that stops the pump should the tank fill before the supply tank is exhausted.A set-up that didn't cause explosions would be a bonus.Any thoughts?

author: Muttley Snickers
author_rank: Unknown
timestamp: February 26, 2016, 08:53:21 am
content: I use and make my own jiggler syphons in various sizes and they do the job just fine, otherwise have a look at the gear Whitworths have available.https://www.whitworths.com.au/

author: jeroen79
author_rank: Frequent Contributor
timestamp: February 26, 2016, 05:34:49 pm
content: Does the tank already have a fuellevel sensor?Can you modify the tank?In that case all kinds of fuelsensors are commercially available.DIY could use a float with an optical sensor or magnetic sensor that closes a contact when the tank is full.The fuelnozzles at gasstations have an autoshutoff that works by sensing the air pressure at the end of the nozzle.

author: davebb
author_rank: Frequent Contributor
timestamp: February 26, 2016, 05:48:25 pm
content: Hi you could try a boat bilge pump, I don't know if it will be ok with fuel? the pump goes in to the fuelDave

author: rich
author_rank: Frequent Contributor
timestamp: February 26, 2016, 06:47:33 pm
content: Petrol or diesel?Did you specifically want to make something yourself as 12V diesel transfer pumps with automatic cutoff nozzles and fuel meters aren't massively expensive. Here's an arbitrary example (the cut off nozzle is an option):http://www.centretank.com/products/detail/piusi-pico-drum-mounted-diesel-transfer-pumpFor safety having the outlet sense and cut seems sensible. Youcouldinstall a gauge into the tank but that runs the uncertainty of correctly hooking it to the dispensing equipment each time.Usually (always?) there is an air tube in filling station nozzles sucking in air and when it gets blocked with fuel the pressure change triggers the sprung loaded cut out. There are plenty of small electrical pressure sensors available, here though I think the challenge is more in designing the correct layout of fuel and air pathways in the nozzle. I'm definitely not qualified for that part

author: RobertBG
author_rank: Regular Contributor
timestamp: February 26, 2016, 07:43:47 pm
content: Quote from: davebb on February 26, 2016, 05:48:25 pmPLEASE steer clear of a bilge pump for this,if you've ever seen gasoline vapors blow a boat to bits you'll understand why.The simplest solution I've seen was a float switch where the float rides along the fill tube.The length of tubing works as a fill nozle and when the float reaches the switch it cuts the fuel pump off.You simply open the tank and drop the tube in and turn it on.As long as it is the right length it works like a charm and to help the pump you can also use holes along the length of metal tubing up until the upper part of the tank.Or you can also design it to hang from the fill with a shorter tube as long as the float is able to move freely.Just be sure to use a proper pump and float/switch assembly,if you're on a budget chances are you can find most of what you need in a junk yard

author: Gyro
author_rank: Super Contributor
timestamp: February 27, 2016, 10:14:12 am
content: Not wishing to inject too much of a note of caution, but Europe's biggest peacetime explosion occurred in 2005 at the Buncefield fuel storage facility roughly north of London. It measured 2.4 on the Richter scale and was heard as far away as Belgium, France, and the Netherlands.The cause.... Failure to detect that a tank that was being filled was already full, due to a probably faulty level detector!https://en.wikipedia.org/wiki/Buncefield_fireJust saying that you need to be really, really careful about the reliability of whatever sensor you use, what happens to the displaced fuel vapor, possible overflow, and any possibility of either of them getting near any switching contacts, motor, connections, fuses, etc. If the tank is hard to reach then that implies a confined space such vapor could collect! Even installing it might void your insurance.

author: tggzzz
author_rank: Super Contributor
timestamp: February 27, 2016, 10:17:30 am
content: Quote from: Ed.Kloonk on February 26, 2016, 07:56:27 amDrat. That rules out my suggestion for stopping the pump.

author: Ian.M
author_rank: Super Contributor
timestamp: February 27, 2016, 10:55:54 am
content: One option that might be suitable would be to run a return line back to the portable tank to provide its vent. The return line would be terminated something like 1" back from the tip of the fill nozzle (or be T-ed into the vent line for a fixed installation) and all connections to the portable tank would need to be vacuum tight. Any overfill would be sucked up the return line back to the portable tank and that could continue indefinitely without problems. For belt&braces protection, you'd also have a fuel sensor (e.g. a self-heated bead thermistor) to shut off the pump and operate anti-syphon valves. N.B. A return line will not work if the portable tank is too large as the amount of fuel that has to be dispensed to pull enough vacuum to make the return line suck up the overfill as fast as it is being dispensed is likely to be greater than the reserve capacity in the filler neck.Obviously all pumps, valves, fittings etc. + the thermistor probe must be rated for the fuel used. The power delivered to the thermistor probe must be strictly controlled low voltage low current so that even under dual fault conditions, it cannot approach the auto-ignition temperature of the fuel and to minimize any spark energy, and it must be totally enclosed by an explosion-proof metal gauze to prevent any local ignition propagating to the tanks' headspaces.

author: RobertBG
author_rank: Regular Contributor
timestamp: February 27, 2016, 05:54:25 pm
content: One thing that you dont want to overlook is static electricity,one spark is enough to ignite the fumes in a tank.If you take a look at your cars fill you'll see a ground strap and hopefully your tank is grounded.It is also a good reason to avoid any sort of plastic fill device as they will create static while filling the tank whereas a metal fill is self grounding in most cases.I forget the exact equation but essentially one pint of gasoline that has evaporated is enough to cause a 50ft boat to explode into flames,but its a different case if you simply toss a match into it in a pint glass.This is why it is pounded into peoples heads to always run the bilge glower and or open a hatch while refuelingWhen I was younger I worked summers at my friends marina running the fuel dock and saw one boat blow the hatches off and burst into flames because of a few drops spilled from a vent hose that had come off.Luckily no one was seriously injured but the blast was enough to throw one of them over the gunnels of a 30 ft'er into the water and the boat was a total loss as we had to cut her loose and send it adrift.It burnt to the waterline in about 10-15 minutes.I currently do a bit of composite work for a few companies(Viking and Egg Harbor Yachts)and most of what you need to stay safe can be found in the ABYC Standards.http://abycinc.org/?page=standardsindexI dont know if the info is available to nonmembers through that link but I'm pretty sure you can sign up for a 3 or 5 day trial membership for free.

author: woodchips
author_rank: Frequent Contributor
timestamp: February 27, 2016, 07:46:39 pm
content: Never, ever, pump petrol from cans to anywhere, it is far too dangerous. See photo above!

author: Ian.M
author_rank: Super Contributor
timestamp: February 27, 2016, 08:06:20 pm
content: With the right equipment, and a fully trained operator its reasonably safe.There are even commercial products for exactly that purpose.e.g.https://www.fueltankshop.co.uk/120-litre-adr-petrol-dispenser-12v-pump-cemo-ks-mobile-easy/p4480Use the wrong pump, nozzle, omit a safe static discharge path, let the fumes get into an enclosed space or let an untrained operator use the system and you'd probably be safer juggling live hand grenades.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: February 28, 2016, 03:08:02 am
content: Quote from: woodchips on February 27, 2016, 07:46:39 pmThe Concorde aircraft is a fine example of how fuel can be safely pumped in and around it's various fuel tanks.

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: February 28, 2016, 05:29:54 am
content: Ed- Not the best example to give !Incidentally, many commercial airliners pump fuel between tanks to rebalance the aircraft in the cruise when the centre of lift moves at high speed. Many have tanks specifically for this purpose, usually in the tail to give max moment. This eliminates the need to use aerodynamic surfaces for trimming, which would cause drag and thus increase fuel consumption.BT