Cutting Gas Volume Loss

Have the temperatures and pressures of the bulk gas containers been checked? Using the gas will cause a lowering of temperature and pressure at the container. The container pressure might drop below that set at the pressure regulator, leading to a reduction of flow...

This is a good point to start. I have seen this phenomen a lot at home in my PNG driven water heater during the winter.

Also, check if all the pressure regulators, solenoid valves and these things in the line are for high flow. With increase in flow, they may cause a significant pressure drop.

Is there any chance that a moving part of your machine is somehow biting a supply hose?

I don't think it's possible or reasonable because I don't know your facility or even how often it occurs, but you could try to simply install a cheap manometer with a drag pointer and see how much the pressure dropped in your machine inlet. If it dropped or not, you can determine if it's your source or equipment is bad.

Is one, or are both, of the pressure regulators freezing as a result of gas expansion?

P1 x V1 / T1 = P2 x V2 / T2

- that sort of thing...

There is missing information:

Is this the only cutting torch that is "dropping" when cutting thick plates?

What is the pressure on the torch side of the final regulator?

While liquefied gas tanks will certainly drop way down in pressure at high flows, this would likely affect other torches as well, unless the torch regulators were set lower. Compressed tanks are at such a high pressure, the only effect at high flows would be that the regulator would get very cold which could easily effect its output, but again this would likely effect other torches as well.

If the problem is only with the one torch when cutting thick plates, that is where to look: in that circuit, the torch itself, how the machine moves the torch, etc.

The volume of tanks can be determined by placing them on a scale. With an electronic scale with data output, and a pressure transducer, volume and pressure can be read and recorded by either a computer, data logger, chart recorder, etc.

did you have heater on oxygen supply? could be freezing.

Suggest manifolding Oxygen downstream of regulators.Also LPG/Acetylene bus from start.

Try Two O2 cylinders to start.Operate your Cut with just one Cylinder.

At first appearance of "choking"-open 2nd one--if this restarts GOOD cut ,try shutting 1st Cylinder. If now " choking" reappears, open second Cylinder again.If now Cut is going fine--let it go on that way. Watch it.

If the cutting goes on fine-you will do well to change over to a manifold at the 160 PSI level as routine.

If that did not solve--you get Instrumentation/Data logging and Ph.D's to solve this.