Hi Morgan

I see you have not yet had an answer to your question, so I will hazard a guess, because I do not know the answer to your question for sure. At least we can try to get some debate going here.

Acetylene is a bit of a problem child from a use and storage point of view. Under the pressures that are required for use in welding and cutting, it is rather unstable. It undergoes an exothermic reaction that can result in the cylinder exploding. A bad news scenario!

For this reason, acetylene is not merely compressed and fed into a cylinder like other fuel gasses. (e.g. Propane) Instead, it is disolved in acetone.

Acetylene cylinders contain a sponge like core into which the acetone gets absorbed. In turn, the acetylene is disolved in the acetone. This arrangement has proven to drastically reduce the chances of the "bad news" exothermic reaction from taking place.

The information so far, I am relatively sure of. Now comes the speculative part...

I would think that the longer a cylinder is stored, the greater the chances become of something going wrong with this whole storage arrangement. Typical problems that you could encounter are:

1) The cylinder "core" is damaged. - In this case, there may be "pockets" of free acetylene that could lead to the "dreaded" reaction. Obviously such damage could occur within a short period of time, but if the acetylene is used rapidly the problem should (hopefully) be spotted by the people re-filling the cylinder and fixed.
2) The acetone leaks out, or comes out of the cylinder due to withdrawal rates being too high. Again, a large pocket of acetylene will form that can give rise to the reaction. Again, by keeping a cylinder turning around rapidly to the re-filler, any problem encountered can be fixed by the re-filler. (e.g. add more acetone)

Just to add another interesting piece of news: This exothermic reaction has occurred within cylinders that have been filled according to the right procedures, when something goes wrong. (e.g. the cylinder becomes too hot.) What I am trying to say, is that this is not a theoretical thing. It actually happens from time to time. I would not really mess with this stuff too much, especially if you are going to store it in your garrage, close to your family! If they say give it back to us within six months, I would preffer to follow their instructions.

I hope that my reasoning makes sense.

Regards
Niekie Jooste
Fabristruct Solutions