is this right?
Pure acetylene is a very unstable gas, and if pressurized beyond 30PSI it is going to explode.
The explosion is called a Deflagration, and requires no spark or oxygen.
The hyper-complex acetylene molecule just disintegrates, generating an enormous amount of heat.
This makes it very dangerous to store or transport in it's pure state.
This also explains the BIG RED BAR at 15 PSI on an acetylene regulator's line pressure gauge.
Beyond 15 PSI you are in the danger zone.
There is never any reason to go above 10 PSI on acetylene.

Think of the acetylene bottle as a 2 litre pop bottle.

In a pop bottle CO2 is dissolved in water.
When you loosen the bottle cap, the CO2 starts percolating out of the water.

In an acetylene tank the acetylene is dissolved in acetone.
This stabilizes the acetylene for transport and storage.

Inside an acetylene tank there is very little acetylene.
The majority of the tank is filled with a porous plaster.
The plaster is saturated with acetone.

The problem with this system is that when the tank is set on it's side, the acetone will settle into the valve head.
When you open the valve, the acetone will be spewed into the regulator.
In most acetylene tanks the acetone is so old that it looks more like maple syrup.
You do NOT want it in your regulator.

To avoid this, if a tank is transported or stored on it's side, it must be left upright for at least 12 hours to make sure that the liquid acetone is settled back into the plaster.