Minimum energy for explosion ignition
Minimum energy for explosion ignition
(OP)
the minimum ignition energy is 100 micro joules. we have a pressure switch rated 28 VDC at 0.5 amp to be installed in a fuel tank.
how can we show any spark/arc (during break and make) is below 100 micro joules?
thanks.
how can we show any spark/arc (during break and make) is below 100 micro joules?
thanks.





RE: Minimum energy for explosion ignition
FWIW, you might try posting this in the Electronic Engineering forum, where more sparkies are likely to lurk. If you do that, just post a link back to this question, don't repost your question there, that is considered rude.
RE: Minimum energy for explosion ignition
i do not see electronic group in this eng-tip. have a link?
if energy = 0.5 * L * I^2, L will be, for 100 uJ, 800 microH. if the system has no solenoids... is this L number too high for all the wiring?
RE: Minimum energy for explosion ignition
RE: Minimum energy for explosion ignition
I ask because of a real incident at a small refinery.
The product was lubricating oil. On the line to the loading dock, there was a full flow paper filter to ensure that no particulate matter was shipped. Unfortunately the filter built up large static charges in the lube oil. As the oil was loaded into the tank trucks, it was common for the drivers to report seeing static discharge sparks in the oil.
The energy of the discharges was well below the ignition point of the lube oil.
Then one day a truck delivered a load of gasoline and then came to the refinery to load lube oil.
Unfortunately the static discharge energy was well able to ignite gasoline fumes.
The explosion blew the driver (who was on top of the tank watching the loading level) up into the air.
He may have died from the explosion, he may have died from the fall, he may have died from the burns.
Somewhat moot. He died.
Do a google search on intrinsically safe devices.
Consider methods to locate the pressure switch out of the hazardous area.
Another possibility may be an intrinsically safe transducer outside the hazardous area with an intrinsically safe pressure sensor in the tank.
This thread has an old tune running through my head:
To the tune of My Bonny Lies Over the Ocean.
My Bonny leaned over the gas tank.
To see what the level might be.
I lighted a match to assist her.
Oh bring back my Bonny to me!
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Minimum energy for explosion ignition
I'm not sure how you guarantee someone doesn't come along and drop a huge inductor into your circuit because they're having a "noise problem" somewhere.
In industry the requirements to prevent explosive mixture ignition in a case like this always requires a 'barrier' which is a certified piece of equipment that actually does guarantee that enough energy can never get to an interruption inside the hazardous area.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Minimum energy for explosion ignition
What Kind of Fuel: Gasoline [Octane X]? Jet Fuel [Y]? Diesel Fuel [Z]?
Perhaps You should consider stepping the sensor voltage and current waaay down... outside of the tank environment.
I have seen static electricity arc/spark and start detonations in tactical aircraft fuel tanks [JP-4... really bad]... only to be 'arrested' within a few inches by the polyurethane ballistic foam stuffed into the tanks and large tubing.
I am sure that fuel quantity sensor manufacturers have this problem and may be willing to share their expertise for $$.
Regards, Wil Taylor
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RE: Minimum energy for explosion ignition