Pressure cookers - a word of warning to the wise

My modern pressure cooker has a latch which first releases the spring that keeps the pressure in, and then releases the lid. (The spring also allows different pressures to be set.)

My old pressure cooker is from 1924 or so: no lugs. It can be opened under pressure, though the force required is much greater than when not under pressure.

It has a new lid gasket, a new rubber plug thing (and a new jigglything, because I broke the old one by overenthusiastic cleaning). These were in stock in a small hardware store in a (leftpondian) village -- these parts fit any pressure cooker of that size for the past ~100 years, apparently...

Thomas Prufer

I have never known a safety valve to operate on a pressure cooker.

Can you explain why the weights did not "lift" allowing sufficient steam to vent when the pressure in the vessel had risen to the prescribed pressure?

Do you have photos of the safety valve, or the website page you got this part from?

As I said earlier: I had fitted the safety valve upside-down and the whole valve was ejected, presumable before the pressure was enough to lift the (H) weights. Surprisingly the valve was bought from a local hardware shop, rather than the web - the pack looked like this:

Not with the ones I am thinking of... Similar to:

The lid was held worn by pressure from the bar - if you slackened that under pressure it would start to vent from the main lid seal.

(Note that modern versions like that pictured, may include some mechanism to prevent this)

Never tried one of those... how do they regulate the pressure then?

ISTR recall a friend of the family from way back had one operate - she did not have enough liquid in it, and allowed it to boil dry. So the pintle in the valve melted and let by.

(I think it shook her up a bit, since after that she would always leave the room when it was on!)

Found this when looking for that answer - may be of interest.

Thanks for the clarification, I misunderstood and thought there was some other, more serious, catastrophic failure.

I can see how easy it would be to fit the wrong way!

I have no idea how safe pressure cookers are as they're not generally tested after a few years of use, unlike any other pressure vessel. Yet I have never known one to fail. They were all the vogue a few decades ago, probably when most cooks felt their duty was to cook veg within an inch of annihilation?

I must admit as a child I would feel unhappy being in the same room as one!

The also don't operate at huge pressures in comparison to most "real" pressure vessels... even a normal *vented* domestic cylinder can be operating at a higher pressure in a tall Victorian property.

The main attraction ISTR was the speed of cooking, plus a bit of energy saving and efficiency (where you could do several things at once in them with the added baskets etc)

Fascinated by the "multipack". I have one of those type of pressure cookers (and have had for 30 years) in that time I have had to replace that little thingy once - as the rubber got very hard and the device would fall out - into the pan - with very little encouragement.

Whilst I needed one replacement the chance of ever using (or finding) the other would be remote.

A couple of links that use pictures better than I can use words:

The safety valve lifts when the desired pressure/temperature has been reached. The operator should then reduce the heat so it just closes.

They are massively over constructed. The chance of failure is extremely remote. I suppose that metal fatigue will get them in the end after many thousands of cycles.

They highest setting is normally 15psi. The energy locked up due to enthalpy is easily enough to kill you. Especially if there was too much water in the the thing, thus storing even more energy.

Precisely, not a demanding application.

That wasn't quite how the instructions for our Prestige told you to do it. The safety valve should stay up for the whole cooking time. The adjustable pressure control by the handle vented steam to indicate 'up to pressure' and you reduced the heat shortly afterwards. It should remain just slowly venting steam while cooking. At the end of the cooking time, you can't open the cooker until the safety valve 'pin' drops.