Time for review?

Are we not discussing a FUEL TANK ? A sealed unit for all practical purposes and intent?

Fuels are ignited by heat - produced by any number of methods.
Liquids do not burn - vapors do. HEAT increases production of vapors.
Like the goal posts at the end of the football field - when the Lower Flammabiltiy range and the Upper Flammability Range are within those limits, you have only need for ignition.
Three mandatory components -- FUEL - OXYGEN - IGNITION ( almost always HEAT in one form or another)

Dealing with UNKNOWNS -- is a hazardous business, sometimes with very undersirable results, being death or serious injury.
Residual compounds or component may be present even within the pores of the metal in the tank.

How many have heard or known someone that attempted to weld a fuel tank, cut a drum, etc and had an incident, even with those drums and fuel tanks that have sat for years.

Hazardous Materials Emergency Response Training really opened a whole new world to me. There are many terms involved with "combustion or flammabiltiy" but the basics will help to protect you and your loved ones. My awareness is much keener and my RED FLAGS rise much sooner.

Hope this provokes some thought and saves someone injury.

STAY SAFE - there is no guarentee what you "think" is there is or is not present. Even with high quality proven test equipment, failures do occur, many due to improper use or calibration but the results are always less than desirable.

Winter is upon us here in the USA, Northern Hemisphere. Think about your heat source in your shop/garage and those materials that are flammable/combustible.
Where do the vapors reside? Rise or Sink?

CTS

Hi, Folks.
Here izza link to a page with some safety information about gasoline/petrol. It gives the flash point temperatures for a couple of common grades of the fuel beyween 1/3 and 1/2 way down the page, two small sections which are headlined, "Flash Point".

fuelflowpro.com/flash-point-of-gasoline/

I have known for quite a while now just how low these figures are but it did cause my eyebrows to climb justa tad when I learned it.

Just my 0.02.

Here is what happened to one of my neighbors that tried to weld on a diesel tank!

www.findagrave.com/memorial/35836328/bob-alan-hanchera

be careful with heat you can make things worse. not just in the fire explosion risk. something to remember a fuel tank if heated becomes a pressurised container fuels when pressurised go BANG! how big a bang depends on many things. but a point to ponder butane cigarette lighter contains enough explosive power to remove a boot lid from a car. remember a empty or partially full container is more dangerous than a full one as you have more room for vapour.

there is a book written by retired machinist and tafe teacher Wilf Manning. sadly Wilf is no longer around he passed years ago and his book series is no longer in print. the book is "Around Wilf's Workshop" and he discuses many subjects useful to restorers of old machinery. one of them being freeing stuck components especially fasteners and how heat can make the situation worse if applied wrong. dad has 1 book out of the series of three.

after all the things i have done over the years without bad things happening . , anymore i use a nitrigen gas purge with a good flow to keep welding , heating or other kinds of ways to cause ignition at bay

Dry ice can be a convenient way to purge a tank of oxygen. Also exhaust from an internal combination engine.

This subject has been broached by multitudes in many different venues. Volumes of materials written, documented cases of incidents, and to some of us, very personal experiences.

Regulations, rules, laws, do not prevent death or injury, it is up to "you" to protect yourself and others around you! SAFETY DOES START WITH YOU!

(1) Dry Ice is FROZEN Carbon Dioxide, as it "melts" it returns to a vapor. (The frozen state also condenses the volume, thus when it does "thaw" it can result in over pressurization of the vessel if it is contained or trapped.) Nothing states where those vapors of non-combustible gases may or may not leave a pocket of combustable vapors! Other fittings, dents, bulges, are all possible sources of pockets.
(2) Exhaust from any internal combustion engine - nothing says it does not contain unburned fuels, that is one of the problems with any combustion product ( IE - Exhaust Gases)
(3) Many methods have been used, some with satisfactory (no injury or death) and others that did not come out well.

Heat of any type and fuel are a perfect recipe for disaster. The presence of "oxygen" can be in several forms or compounds. One mentioned "Rust", the product of oxidation of iron/steel. Key being OXYGEN. Many forms of oxidizers exist, all producing oxygen.

There was a reason behind using BRASS for fuel caps and many specialized tools are made specifically for combustible/flammable environments. SPARKS ARE IGNITION HEAT SOURCES.

Please remember the "triangle", any one leg broken, combustion "MAY" not occur, but that is under "PERFECT" and absolute conditions. Very seldom do any of us work under perfect conditions!

There is a saying used in HAZMAT Response --- RISK vs GAIN
Weigh the risks vs the gains!
For example - what is that fuel cap worth? Certainly not the risk of an uncontained explosion resulting in bodily injury or death. Both have been well illustrated over many years.

I apologize for "beating this drum to a pulp", howerver, I do not want to learn of you or your loved ones hurt or worse.

THINK - BE INFORMED - PLAN AND EXECUTE.

STAY SAFE!
CTS

Don't let yourself think just because the tank has sat empty for years you are safe ether. The way modern gas goes bad you well could be. But it might have been 60 year old gas rather than 30 year old gas. Back in the 80's I saw the after math of a old empty 55 gal drum. The scraper was only cutting the bands holding it a DW 20 water wagon. It was the last thing he ever cut. Was not a pretty site.

Neil, I have not got back to it yet and 3 or 4 days of rain are here. I certainly did not expect this many comments on my post. Lots of interesting ideas. Thanks to all, Grant.