Originally Posted by Selkie
This guy doesn't take into account the change in external atmospheric pressure pressing the escape value weight against the valve hole. His calculations don't compensate for change (sea level vs 10,000 ft.). They only speak to a static setup.
As both a pilot and a submariner, I have just a little experience with changing pressure differentials, not that I claim to be without fault. It has been a while since I had work a problem like this, and my aging brain is admittedly rusty.
Now it's time for me to go soak my head! Where's my scotch?
I too worked on submersibles, the U.S. Navy DSRV. Yes the pressure exerted on the hull of a submersible does affect the inside pressure of the vessel, just as elevation requires aircraft to compensate by pressurizing the cabin. However, in both cases, the inner pressure is compensated to a degree by the rigidity of the vessel walls. The inside environment of the Steel spheres of the DSRV resist the intense pressure exerted by the outside water at great depths. This allows the occupants to stay in an atmospheric environment that will not crush them, or even cause excess gasses to dissolve in their bodily fluids. This allows them to safely travel to the surface with no ill effects.
This pressure mechanism is independent of the outside pressure forces, within allowable limits, which is determined by the strength of the materials used to make the spheres.
A scuba diver, on the other had, is subject to the full force of the water pressure. His tank remains at an internal pressure, when full, of 3000 lbs. until he starts breathing. The airflow to him through the regulator is dependant on the water pressure, which when the ambient pressure increases, it presses on a diaphragm, or valve to open the orifice more, and allow a greater pressure of air to flow to the diver. This provides sufficient pressure to allow his/her lungs to inflate properly, even though there is more pressure exerted by the body.
Like the submarine, the PC is a vessel designed to capture and maintain a pressure load, regulated by a weight that requires a certain amount of pressure to lift it and allow steam to escape. Notice that pressure cookers are not designed to work horizontally, but the valve points upward. The weight of the regulator presses down over a tiny orifice, trapping the air inside the PC. When sufficient pressure is achieved to lift the regulator from that orifice, pressure is released. The regulator weight is literally dancing above the orifice on a column of upward moving steam. If more weight is applied to the regulator cap, it takes more pressure to lift it. That's why I said that the main forces that create pressure in the pot are the excitation of liquid, and heating vapor working against the weight, which is a function of gravity and mass. I thus propose that the temperature inside the PC is independent of atmospheric pressure, as that pressure is exerted from every angle, and does not press the weight against the release orifice.
And yes, I dove as well as working on the DSRV. Neither activity qualifies me as a pressure expert. Selkie, if you can produce recognized documents to support your theory, I will step back and state that I was wrong and learned something new.
As to the original question posted by the OP, Check your pressure cooker to verify that all seals, and valves are working correctly. You may have to turn in your new pressure cooker as defective, and obtain a replacement. Again, if you know anyone with a pressure cooker in your area, that would be where the best advice would come from.
One more bit of factual info to support my argument. The weight of air is greater the closer you get to the center of the Earth. The heavier air has greater density that the air above it. When a ballon is filled with hot air, the density of the air is less than that of the air around it. If air pressure pushed downward, the balloon would stay down, as the air around it is heavier. Instead, the more dense air at the bottom pushes the balloon upward. This phenomenon is called bouancy. The air at the bottom of the weight is actually pushing the regulator upward, but with negligible force. The lesser pressure exerted at higher altitudes still works the same way as the air at the bottom of the weight is more dense than the air above the weight.
Seeeeeeeya; Chief Longwind of the North