Can pressure cookers accidentally explode when trying to cook with them – quora gas prices


The deal with pressure cookers is that they have a metal interlocking lid that can withstand a great deal of pressure, and a gasket to keep things airtight. And then they have a relief valve that lets out steam to keep things at a constant, useful pressure.

The older cookers from the 1950s and before had a single simple mechanical weighted pressure regulator that could get stuck or clogged by cooking debris, and then the pressure would build up inside without regulation. At some point something is going to give, either the gasket blows out or the valve becomes dislodged or opens suddenly, causing a violent ejection of steam and possibly cooking liquids. Making matters worse, the sudden pressure reduction lowers the boiling point, creating more steam, kind of like a damaged soda can that springs a leak.

If a cooker could build up enough pressure the lid latch could fail and send the lid flying — but due to the mechanics it wouldn’t go very far, probably champagne cork speed at best. It seems even more unlikely that the vessel itself would fail explosively. The reason it doesn’t come to that is that as long as the pressure builds up at a reasonable rate (as opposed to somebody intentionally making a bomb) it will fail at the weakest point, and that’s usually the valve or the seal.

The two bigger dangers, which are still the biggest risks today, are that people will either put their face in front of the relief valve and get scalded by steam that is released during normal operation, or else open the lid after cooking before the pressure inside has a chance to equalize, and then they get boiling liquid and steam shooting out through the gap as it opens. I suppose contents being hotter than normal is also a risk, they cook at about 250 degrees fahrenheit instead of 212 degrees or less for conventional boiling and simmering.

Between the 1950s and the 1980s pressure cookers in the US all got better valves, and sometimes secondary relief valves. They also started making lid handles with latches that would only open at safe pressures, although if you’re persistent or they’re wearing out you might be able to jiggle and force them. Some have additional safety features as well. It’s a safe way of cooking things, safer than pan frying with hot oil that can splatter, spill, or catch on fire. I just wouldn’t put my face directly in front of it or any cooking vessel.

Here’s an article on safe cooking practices, Pressure Cooker Safety. Basically, keep it clean, check the condition of the valve and the gasket (which should be replaced if it gets dry and cracked), don’t overfill, be sure to include some liquid but not deep oil, and don’t cook foods that froth. Most important, don’t try to force the lid off if the pressure hasn’t equalized.

First generation pressure cookers use a weight to control the build up of pressure within the cooking vessel and relied upon that single valve to release any excess pressure but if the weight was accidentally knocked off, a messy eruption could occur, or that single valve could potentially get blocked. A popular form of this were the “jiggle top” style, and later models had a secondary manual pressure release valve to supplement the weight for a more controlled pressure release.

Newer (second generation) pressure cookers have triple-redundant safety features to prevent overpressurization accidents. Not only is there the main pressure regulator, which is now a spring loaded valve that cannot be accidentally knocked off, there is also a pressure interlock that locks the lid in place and prevents the lid from being removed or opened while the vessel is pressurized, and finally there is a engineered failure point in the sealing gasket that will blow out and release the pressure in the event that the main valve is clogged and well before too much pressure can build.

This is our pressure canner. See that little black dot at the bottom of the picture? That’s a hard rubber safety plug which is designed to fail and release the pressure inside if it ever gets to about 20 psig. They used to be made of lead crimped into a set of steel threads. The weight is set to 15 psig and the cookers are typically designed so that the lid grips/lock/gasket won’t fail until they reach 3x working pressure.

Be sure to keep the weight stem clean and clear, and clean the inside of the weight, along with the gasket and lid lock mechanism, every time you use it. And please be sure to R.T.F.M. (Read The Freaking Manual) because even though it won’t kill you if you make a mistake, it could blow the safety plug if you annoy it, which will cause you to need a fresh set of skivvies.

Fortunately no one was hurt, though our ears all rang for a few hours and it scared the bejesus out of everyone. The umm… pot roast, such as it was, had pretty much distributed itself across the rest of the kitchen ceiling and the dog was eyeballing the manna from heaven somewhat suspiciously as it lay steaming on the linoleum.

After he put all those facts into my head, he explained that the 3/8″ hole the safety plug would leave if it failed (as it was designed to do) would allow all the pressure to escape quickly and ^safely^ in much the same way a much bigger safety valve I’d seen at Bull Run power plant do. It would be loud, but it wouldn’t hurt anyone.