Pressure Cooker question - Boiling or not?

[Raxs]

Hi everyone,

 

So I've got one of those Kuhn Rikon Duromatic pressure cookers - and until recently, I thought it was working fine.

 

Then I was reading at SeriousEats.com - and came across this quote about making stock in your pressure cooker:

 

A pressure cooker solves both of these problems. Not only does the higher pressure achieved inside a pressure cooker allow you to heat water to a higher temperature (up to around 250°F, or 120°C), but it also prevents the water from boiling, leading to less agitation. The end result? Rapid body and flavor and great clarity.

 

But when I use my pressure cooker (even with just water in it as I tested last night) I can hear it vigorously boiling when it comes up to, and holds pressure.

 

Even on low heat, just maintaining pressure, I can hear the water inside bubbling at what sounds like a full boil.

 

So, I guess the question is: Is this how it's supposed to work? Do I have a defective model?

 

Thanks for any input.

 

R.

[gfweb]

When you are at pressure, is there a lot of steam escaping?

[Raxs]

Not a ton, but a little here and there in spurts - and the pressure still reaches the full two bars in a few minutes if I start it on high.

 

The boiling is the dominant sound coming from it.

[Yiannos]

I'm not an expert by any stretch but it sounds like it's possible you don't have a good seal? I remember running the initial test on mine but do not remember any distinct boiling sounds, I'm wondering if yours is not sealing right and so unable to build the pressure needed to tamp down the water action.

[Cyberider]

The water has to boil and vaporize in order to build up pressure.  Sounds normal to me.

[boilsover]

From Moderist Cuisine at Home:  " Water vaporizes into steam, increasing the pressure inside the cooker as it heats.  Because the boiling point of water depends on pressure, it rises too [sic] just enough to keep the water and steam temperature hovering around the boiling point for the higher pressure. The pressure continues to rise until it is stabilized by the valve."

 

I think you need to turn down the heat...

[Martin Fisher]

The same question was asked previously — here.

 

 

[Raxs]

Ah! Thanks. I did a search but didn't come across that one.

 

So it seems like it's malfunctioning? I'll test it again tonight and bring it up to pressure much more slowly and see if I can reach 15 bar or so without it bubbling away.

 

R.

[JoNorvelleWalker]

Don't know if it helps, but after my Fissler reaches pressure it does not make boiling noises.

 

[dcarch]

6 hours ago, JoNorvelleWalker said:

Don't know if it helps, but after my Fissler reaches pressure it does not make boiling noises.

 

 

You may not be able to hear the sound boiling makes. PC has very thick walls.

The only way a PC keeps pressure is by boiling water inside.

 

dcarch

[boilsover]

14 hours ago, dcarch said:

 

The only way a PC keeps pressure is by boiling water inside.

 

 

 

This is not entirely true.  In a sealed environment, there will be vapor pressure generated below the boiling point dictated by the system's valve.  It would be better to say that the PC will hold pressure until it exceeds the valve setting or the system cools.  

[dcarch]

1 minute ago, boilsover said:

 

This is not entirely true.  In a sealed environment, there will be vapor pressure generated below the boiling point dictated by the system's valve.  It would be better to say that the PC will hold pressure until it exceeds the valve setting or the system cools.  

 

In reality, The metal walls of the PC constantly radiates a lot of heat (BTU lost), in order to maintain pressure due to heat lost, the water inside has to be boiled all the time, even there is no steam lost from the valve.

 

dcarchh

[boilsover]

2 minutes ago, dcarch said:

 

In reality, The metal walls of the PC constantly radiates a lot of heat (BTU lost), in order to maintain pressure due to heat lost, the water inside has to be boiled all the time, even there is no steam lost from the valve.

 

dcarchh

 

Well, this is one reason most PCs are made of stainless steel--that material's exceedingly poor conductivity results in a lucky lack of thermal diffusivity and emissivity.  In other words, they're intentionally designed to radiate little heat.

 

IMO, it all comes down to the physics of the boiling point under pressure.  With pure water at sea level, you can predict the boiling point with great accuracy.  The trick on models without a pressure gauge is to stabilize the system at a point just below the boil (if you want clear stock).  Many true pressure canners have a real pressure gauge, and if the relief is set at 15psi, you can easily maintain pressure at 10 psi.  Is this water boiling?  No.     

[dcarch]

There is a way to have the high temperature advantage of a PC without boiling. I modified my PC's valve to increase the pressure (therefore the temperature). I would not advice anyone else to do the same.

 

I can keep the pressure below boiling point and still have temperature higher than a typical PC. As a matter of fact, after stock making, the bones can become so soft (cut with a fork soft) that I can eat them. Lot's of nutrition in bones.

 

dcarch 

[Raxs]

I ended up taking the pressure valve apart and re-installing it. That, combined with bringing it up to pressure much slower (on a lower heat setting) seems to have solved the issue. I can't hear it boiling when it's up at full pressure now.

 

It's pretty quite now, but still vents a tiny wisp of steam pretty much continuously.

 

Thanks for all the comments.

 

R.

 

 

 

[boilsover]

13 hours ago, dcarch said:

There is a way to have the high temperature advantage of a PC without boiling. I modified my PC's valve to increase the pressure (therefore the temperature). I would not advice anyone else to do the same.

 

I can keep the pressure below boiling point and still have temperature higher than a typical PC. As a matter of fact, after stock making, the bones can become so soft (cut with a fork soft) that I can eat them. Lot's of nutrition in bones.

 

dcarch 

 

Yes, this is possible--and inadvisable.  You're making my point--you can maintain constant PC pressure without boiling.  The issue for consumers with gaugeless PCs is knowing when to lower the heat before boiling occurs.