[Scoundreller]

I have a Presto pressure cooker. The blowout disk is a piece of rubber/plastic built into the cap. I have a hard time imagining it getting contaminated in a way that surpasses the strength of the stainless steel lips on the lid/pot.

Its design hasn't changed since 1977.

It's not a tube that a bean could get into. Maybe you're thinking of the vent pipe? When that gets clogged, the overpressure plug is what blows away to release all the pressure.

[Piskvorrr]

Well...I have seen the whole lid, firmly embedded in the ceiling. IDK what the brand was, but apparently the failsafe (a rubbery thing, off-center of the lid) failed to fail-safe in that case.

Looking into RAPEX, I see multiple recalls for this specific issue (pressure buildup leading to uncontrolled blowout); all for brand names that are unfamiliar to me.

[Scoundreller]

Of the 12 recalls I found on that database, none specifically mentioned failure of a blowout disc/plug1.

1 depended on the rubber gasket itself as the blowout valve. Several could be opened while under pressure, and some were deemed structurally deficient, which I take to mean that the vessel wasn't (consistently) built to withstand the design pressure (and a margin of safety).

[1] 1 did reach 290kpa (42psi), nearly triple the typical pressure cooker. Not sure what happened on that one.