Thread: oxy acetalyne hose fittings

Originally Posted by Stustoys

Hi Chris,
Nice post but are you sure the water was used for filling Acetylene cylinders?
Stuart

Stuart, yes 100% sure it was water. I believe the adsorption rate of Acetylene in Acetone is very temperature dependant. They need to keep it stable to judge if it is full from the filling time. If underfilled custemrs are unhappy, and I guess oversaturating is not good either. The filling itself happens at about 15bar. The compressor and its tank are kept under water, to exclude any Acetylene leaking getting into contact with air. If interested you cann Google for Acetylene adsorption charts, and you can even find whole descriptions of Acetylene plants. I just found this one as first hit: Acetylene Plants | Acetylene Gas Plants Manufacturer
Chris

Originally Posted by Grahame Collins

Au contaire mon fraire,

The explosion/s are mostly set off due to the affinity of acetylene with oxygen.

Grahame

Grahame,

Two different things.

- The reason Acetylene is not stored like most other commonly used gases under high pressure, but dissolved in a liquid instead, is that it is unstable at high pressures. Acetilene can explode spontaneously at pressures above 2 bar, and it does NOT require the presence of Oxygen to do so!!!

- You are right in that most accidents happen when Acetylene leaks and mixes with air.

Please read this for a better explanation how these two things differ fundamentally: Handbook-Oxygen & Acetylene

Salut, Chris

Chris,
I freely acknowledge that acetylene has the ability to explode spontaneously at pressure of approx. 2 bar-no argument there !

The point is that the likelihood of such explosions being common place is very small in comparison to gas leak explosions and especially those that occur in a confined space mode. the explosions and fatalities that have occurred over the last few years were all gas leaks as far as I know.

If you look at the regulators made probably in the last 10 to 15 years you will find that the commercial quality regulators have been manufactured to mechanically prevent them being wound up over 100 KPa.
That is my experience with regulators going back that far. The very old ones (mickey mouse ears type)prior to the Monitor series could be ,
but apprentices were always warned not to do this..

The reference you gave the link to, Also said the following of acetylene leaks- Ok I was out a bit on the upper limits – but note the wide explosive range.


<The other property of acetylene which you must remember is this: that the flammability range of mixtures of air and acetylene is broader than that of any other fuel gas/air mixture. Let’s explain that more fully: Acetylene/air mixtures can be ignited when they contain anywhere from 2.5 percent acetylene to 80 percent acetylene. Mixtures of methane (the principal component of natural gas) and air are flammable when they contain as little as 5 percent methane and not more than 15 percent methane. The hazards resulting from acetylene leaks are therefore somewhat greater than the hazards involved in leaks of other fuel gases.>

I clearly remember in the seventies 5 men lost their lives when they returned from smoko back into a dragline tub—where they were performing shutdown work- Oxy cutting gouging etc. Someone had not removed the oxy cutting unit which was leaking. When an ignition source was provided- presumably from striking an arc- an explosion occurred in the confined space.

These days confined space entry is much better managed with very defined rules for hot work in confined spaces.


To get back to the original poster’s query, I am concerned that someone may attempt a repair and create a similiar hazardous situation just through lack of experience. Perhaps there is someone close by with experience who can help the poster.

I can see a point in the future where the Nanny state will step in,and one will need a qualification or license just to do some work ,while straight forward ,that still needs the appropriate knowledge and care.

Take care

Grahame

There is a chap I know very well who has a oxy ac welding set , the hoses he uses look like they are 60 years old ... very frayed and worn . This thread has prompted me to remind him to buy new hoses, but its a touchy thing. How do you tell a friend to be more careful without insulting him ? Mike

I worked for CIG/BOC for a decade so I can probably shed a little light on acetylene although my recollection of precise facts is fading over intervening years. We referred to it as DA – Dissolved Acetylene, because it’s dissolved in acetone and the cylinders were filled with a porous mass. I think our production engineers said it was unstable and explosive above 3% i.e. if it exceeded 3% gaseous state and not dissolved in acetone within the cylinder mass. While the cylinders are filling, water trickles over each cylinder to dissapate the heat as it’s dissolving. Acetone will dissolve more acetylene when cooler (15C?)

I can recall three acetylene incidents: the first was around 1991 when the Melbourne (Preston) acetylene filling works blew up after acetylene cylinders were vented prior to refilling. Fortunately no one was injured but CIG had to vacuum several surrounding suburbs to clean up the porous mass resulting from the “acetylene rocket range”.

The second was in the Philippines where a few day prior to my arrival at the plant, staff had filled either an acetylene cylinder with oxygen or an oxygen cylinder with acetylene (I can’t recall which). The cylinder didn’t explode initially until the workers realised what they’d done and began to vent the cylinder. The resultant explosion killed two and injured several others.

The third was when I visited a BOC acetylene works in the UK where they complained about having to pay for dumping the calcium hydroxide (residue after making acetylene). On asking what they did with it previously, they told me they dumped it in the local creek (it’s highly alkaline) but they assured me it was ok since an acid factory further upstream dumped their spent acid which then neutralised the alkaline. Environmental awareness hadn’t reached Bristol back then.
Peter