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WMF Perfect Plus Operating Pressures meets 15 PSI ?

I'm trying to understand the pressure ratings of various Brands
of Pressure Cookers. I'm particularily interested in the

1) WMF Perfect Plus and
2) Kuhn Rikon Duromatic

models, since I'm considering buying either the 7L Kuhn-Rikon or
the 6.5L WMF Perfect Plus.

What I'm reading in various forums is a bit confusing and contradictory.

I see mention here that the WMF pressure falls short of the std 15 PSI, while
the Kuhn Rikon meets that 15 PSI std. But, the official technical specs
I find on the manufacturer sites contradict this. So, I'm puzzled as to
where the information is coming from, that says WMF pressure is lower?

Did someone test and measure the pressures of these brands to verify
the manufacturer's official stated claims?


Maybe someone can help me?

I do need clarification on this PSI rating issue.

On this blog review bit:
http://missvickie.com/res...es/cooksreview-part2.htm

Kuhn Rikon : Low 10 psi, High 15 psi
WMF Perfect Plus: Low 8.5 psi, High 13 psi


we find that WMF is only 13 PSI on high setting, rather than 15 PSI for Kuhn Rikon.

BUT.........!!!

The official WMF Manual
downloadable here:
http://www.wmf.com/wmf/up...BAL_en_20070216_4408.pdf


On manual page 7 (which is PDF page 6) the operating pressures are given:

"First ring: approx. 110 deg C
(operating pressure 45 kPa, regulating pressure 90 kPa)
for delicate foods such as fish or compote"

"Second ring: approx. 119 deg C
(operating pressure 95 kPa, regulating pressure 130 kPa, max. 150 kPa)
for all other foods."


We need to convert these numbers into the familiar PSI and Fahrenheit scales:


A kPa-to-PSI converter can be found here:
http://www.csgnetwork.com/presskpapsicvt.html

A Fahrenheit to Celsius conveerter:
http://www.wbuf.noaa.gov/tempfc.htm

WMF Perfect Plus:

First Ring: approx. 110 deg C == 230 deg F
45 kPa == 6.53 PSI
90 kPa == 13.05 PSI

Second Ring: approx. 119 deg C == 246 deg F
95 kPa == 13.78 PSI
130 kPa == 18.85 PSI
150 kPa == 21.76 PSI



That max pressure of 150 kPa == 21.76 PSI on the WMF is also consistent with the article
from "Pressure Cooker World" located here:
https://www.pressurecooke...ront/-1/article/4849717/

Which also says:

Kuhn Rikon Duromatic 1.20 bar == 17.41 psi
Fagor Duo 1.05 bar == 15.23 psi
WMF Pressure Perfect 1.50 bar == 21.76 psi

Showing that the WMF actually operates at the highest pressures of these pots.


What pot operates at 15 PSI ?

From the Kuhn Rikon technical specs found in

--Technical Service Information "SI102-04e"--

http://homepage.mac.com/r...n-Pressure-DUROMATIC.PDF

which has a nice graph of the pressure and temperature relationship for
the duromatic pots..

Kuhn-Rikon Duromatic Pressure Cookers Technical Specs:

First Ring:
Temp: 229 deg F
Pres: 5.8 PSI

Second Ring:
Temperature: 243 deg F
Pressure: 11.6 PSI
max. Pressure: 17.4 PSI, 254 deg F


Nominally stated 15 PSI is actually operating 11.6 PSI on Kuhn-Rikon Duromatic Pressure Cookers,
not actually at 15 PSI. The explanation given for this by Kuhn-Rikon engineers is that the old
style pots would continually emit bursts of steam, causing a fluctuation of the pressure inside
the pot. So, while the max pressure was 15 PSI, the repeated steam bursts would lower the pressure
inside the pot abruptly, so that the average operating pressure was actually around 11-12 PSI. Since
the newer pots, that do not release steam, were calibrated to cook the food at the same rate as
the old style pots, the operating pressure was set at 11.6 PSI to match the actual old style
cooking pressure, while this pressure was "labeled" 15 PSI to indicate to consumers that its
effectively the same pressure measure of the old pots, so recipies need not be adjusted.

Therefore while the Kuhn Rikon actual high pressure is 11.6 PSI the WMF Perfect Plus is 13.78 PSI.

The WMF is operating at a higher pressure than the Kuhn Rikon !

On the low ring, the Kuhn Rikon actual low pressure is 5.8 PSI, while the WMF Perfect Plus is 6.53 PSI.

So, again the WMF is operating at a higher pressure than the Kuhn Rikon !

The pots blow their safety valves at 17.4 PSI for the Kuhn Rikon, and at 21.76 PSI for WMF.

Once again, the WMF has the higher pressure tolerance.

Neither pot operates at 15 PSI true pressure.

Both operate within the US parameters, but the WMF works at a higher pressure for all levels.

Nominally stated 15 PSI is actually operating 13.78 PSI on WMF Perfect Plus Pressure Cookers,
but only 11.6 PSI on the Kuhn Rikon Duromatic Pressure cookers.

This is if we believe the manufacturer's printed claims.

Has anybody checked this and independently verified or contradicted the manuf specs?

I like the Fagor style, and love the price even better. I even had my heart set on the Fagor Duo set. But, then I read all the reviews, and found too many complaints of Fagor units exploding, and other problems with quality control. On the other hand, almost everybody who owns a Kuhn Rikon or WMF pressure cooker is happy with their pots. I only found one guy who complained that his Kuhn Rikon would not seal properly, and kept leaking from the lid. Other than that, it seems the Kuhn Rikon is the best out there. However, I have a slight preference for the WMF Perfect Plus because of cleaning. I went to my local store to examine the Kuhn Rikon, and the sales person there explained to me how I'd have to clean the valve after cooking foods that froth up like beans, and I realised that the Germans had solved this little problem with their design in the WMF Perfect Plus. I also asked if they had a glass lid for the pot, and the std Kuhn Rikon glass lid they brought out looked so cheap that almost all other pressure cookers out there have a better design and better quality optional glass lid. That got me thinking that the Kuhn Rikon, while popular and a good design, is no longer the best. So, from what I've read, Fagor needs to solve their quality control problems. It's WMF or Kuhn Rikon for me. The Kuhn Rikon has the advantage that it's sold in several local stores near me, and parts are always available. However, it's design is showing age. The WMF disadvantage is that I have to buy online and ship the parts in. That's the only negative point on the WMF unit, from my perspective.

The WMF is just the easiest to clean. Clip off the handle and rinse. But, pressure cookers should not explode. Even if the user does something wrong, the safety features should protect the user from his own error. There are just no reported cases of Kuhn Rikon or WMF exploding. Maybe it's because they are more expensive, so sell fewer units. My guess is that the Fagor sells alot more pressure cookers than both of these top brands combined. And generally speaking, people who find problems complain, while happy consumers often remain silent. So, there's a bias there again in reading reviews. There are many people who claim they've had their Fagor pots for years with no problems. Others say the older units were made in Spain, while the newer units are manufactured in China, and it's only since the manufacturing moved to China that problems with quality control started showing up. I just don't know. Since I will be "a new buyer" what concerns me is the quality of the current new units.

I have to agree that Fagor Design must have been UL approved. Which means that properly manufactured pots should not explode. A search with google for "Fagor explode" will turn up several claims of exploding pots. I can only believe this is due to faulty manufacturing and not faulty design. The Fagor design seems ok. How would a newbie know when he gets a defective pot, however? Unless there are some obvious signs of defects, the user has to trust the pot. Again, maintenance could be a contributing factor. These reviewers don't give detailed accounts of what they did leading up to their exploding pot experience. However, entering "Kuhn Rikon explode" in google, or "WMF explode", turns up no examples of such problems for these brands. Maybe it's Fagor's competitor's writing bad fake reviews to help reduce Fagor sales. Maybe some good reviews are Fagor itself promoting it's own pots. It's impossible to tell on the internet, what you read is true or false. That's why I'm very interested in the PSI ratings of these pots from some independent reviewer who's tested them. I myself thought of getting a spare lid for the WMF Perfect Plus and drilling a hole in the lid to attach a Pressure Guage, then measure the actual pressure myself on a test run. But, I'd think that someone out there must have already done this. I just can't find any websites that describe this testing yet. People say things like "I'm a teater for this brand", but they don't describe their test process. So, the claims are all weak. It's very easy to test these pots. Just buy an extra lid for each brand and model you intend to test and punch a hole in the lid to attach a pressure guage and watch the reading on the guage when the pot's own simple guage measure reaches "ring one", "ring two", and "ring three", etc..But, who has done this, yet? People say they test, without describing a thing about the test process. It's not scientific at all. Just opinions. All opinions may be biased when influenced by the need to make sales. So, I'm not sure what to believe out there. WMF's official website, however, gives me lots of information that makes me confident that this German brand is good. Besides, they've been around sicne 1853. So, they have reputation to uphold.

parker wrote:

---

I have just bought the WMF Perfect Plus 6.5 qt Pressure cooker
in the US and so have a bit more information on this product.

From the Manual page 11,

"The cooking temperature is 226 deg.F for the 1st orange ring
and 239 deg.F for the 2nd orange ring.

This WMF Pressure cooker is bought in the US, and looks identical
to the 6.5 qt WMF sold in Europe. However, the product id codes
are different, and from the manual, it appears that the pots have some
differences.

The first important observation is that the WMF-USA Pressure cookers
operate at a "Lower Pressure" than the WMF Pressure cookers in Europe.

So, it appears that what other people have been saying about WMF is true,
i.e. the pressure is lower than the Kuhn Rikon, "in America".

Art No. 07 9313 6040 -- European Model WMF Perfect Plus 6.5 qt
Art No. 07 9313 9300 -- USA Model WMF Perfect Plus 6.5 qt

The American Model 07-9313-9300, does not give the pressure numbers at which it
operates. This model only mentions the temperature. 226 deg.F and 239 deg.F. for
the 1st and 2nd rings.

The European Model 07-9313-6040, gives both the pressure and temperature numbers
at which it operates. These temperatures equate to 230 deg.F and 246 deg.F for
the 1st and 2nd rings.


The higher temperatures indicate higher pressures.

Putting the numbers in perspective to compare:

1st Ring indicator:
230 deg.F -- 6.53 psi -- WMF Perfect Plus EUROPE, Model# 07-9313-6040
229 deg.F -- 5.80 psi -- Kuhn Rikon 7L
226 deg.F -- ? -- WMF Perfect Plus AMERICA, Model# 07-9313-9300

2nd Ring indicator
246 deg.F -- 13.78 psi -- WMF Perfect Plus EUROPE, Model# 07-9313-6040
243 deg.F -- 11.60 psi -- Kuhn Rikon 7L
239 deg.F -- ? -- WMF Perfect Plus AMERICA, Model# 07-9313-9300

It seems to me that WMF manufactures a cheaper pot for the American Market, but keeps the
look and feel of the pot the same as the better European one, to use it's brand reputation to
sell an inferior product.

I still like the WMF for the ease of cleaning and design. But, I'm not sure what other
differences in quality exist between the American and European versions of this
pressure cooker.

I'm wondering if I can just buy the European spare parts, i.e. the pressure valves, and
upgrade the American pot to the European version, or if there are more substantial changes
under the hood.

But, I think I now understand the confusion of the contradictory reports I've seen around the
internet.

There are two different WMF pots that look alike, so the consumer should check model numbers
carefully to determine which cooking pressures he is buying.

At this point, I give Kuhn Rikon high marks for the least deceptive practices.

WMF deliberately left out the pressure numbers from the American Model Manual, because they
didn't want the consumer to realise that it's a different pot from the well regarded European
version of the same brand.

Also, at the bottom of the WMF America Model there's no mark mentioning the max pressure.
European Pressure Cookers are required to imprint the max pressure on the pots, which is usually
at the outside bottom.

If I find more differences I'll update this thread.