Pat mentioned 100 psi on trucks.
If I've got this right, failure is occurring often enough and without damage (other than the tyres), so experimenting to find a better setup seems reasonable to me. My paragliding teacher used to design his own shutes and there failure is critical - so his approach was to make marginal changes in design and to keep them if they made an improvement. If you can't make bold changes as a test, you could make incremental changes and look at the effect statistically to see if there are improvements.
Tyres are convex. Where they meet the road the road forces the shape to be flat: the inner and outer radius of curvature at the contact patch is effectively infinite. It seems to me that what the pipes are trying to do is make the tyres buckle inwards at the contact patch.
I assume that inward buckling is beyond what the tyres are designed for. CapriRacer seems to be the man in the know - the tyre expert.
The inward buckling would be reduced by higher tyre pressures. On the other hand there is the driving force at the contact patch which is trying to shear the tread off tyre. The purpose of dropping the pressure from 70 psi to 45 psi might have been to increase the size of the contact patch and therefore reduce this shearing force on any square inch of the contact patch.
On a safety note, are workers well clear of the machine when it is in operation? If tyre failure was considered unlikely when the machine was designed and is now a common occurence in operation ... ugh.
We haven't mentioned horsepower. Are the pipes brutally brought up to speed to get the job done as fast as possible, or gently spun up to speed? If the spin-up time is short, ie the motor is very powerful, can this be done slower, as a test.
The same for stopping. Is the motor turned off or gently brought back down from running power to zero?
On Pat's point about solid rubber tyres, I believe the reason we have air in tyres is passenger comfort on undulating surfaces. You have neither passengers nor undulating surfaces. I'm no tyre expert; these are just my thoughts.
If increasing tyre pressure causes failure due to more shearing on a smaller contact patch, and lowering pressures causes failure due to the tyres buckling inwards, then I'd be tempted to say the curvature of the pipes (compared to the flatness of a road) is the cause of the problem and I'd wonder if using more wheels would be a solution.
There are no strange chemicals coming into contact with the tyres are there? THey aren't getting covered with cement dust or whatever. [Not that I would expect cement dust to influence tyres. I just ask so that we can eliminate chemical attack as a possible cause.]
Sorry for the disjointed nature of this posting - I am being pestered to go an eat!