Does Underwater IP (aka MP) Gauge Exist?

[PhilEllis]

So the gauge was reading 205 psi then?

135psi base IP
+ (4 atm*14.7psi) Ambient
+ (Apeks magical overbalancing number +10 psi?)

The IP was reading 142 psi at the surface and at 125 feet deep, it was reading 152 psi.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

 

[beanojones]

I got a little lost somewhere in this thread, how about telling us what you are trying to do and we can make suggestions from there. If I repeat anything that has already been stated, please excuse me…I'm old.

What I want to do is measure the pressure in the hoses, not the pressure in the hoses over the ambient.

It seems like I could waste a gauge but then I would only be able to read pressure over ambient.

Was the testing done by DiveSports done dry, or in the ocean? Did you try it with other regs to see if it was only the Apeks that ended up with higher IPs?

(This does in fact hit back on an interesting (to me) point LuisH touched on. He suggested that a regulator could be test dove dry. But a chamber dive is not an ocean dive. It may tell you something about how a reg works, but it is hopefully not how APeks tested their dry environmental chamber design.)

I wonder if the 'over-balancing' was an intentional design, or an artifact of the design that was marketed as a feature.

 

[redacted]

What I want to do is measure the pressure in the hoses, not the pressure in the hoses over the ambient..

If the gauge is balanced for the known ambient pressure and you measure the gauge pressure then the pressure in the hose is the sum of the gauge pressure and the known ambient pressure.

 

[Luis H]

What I want to do is measure the pressure in the hoses, not the pressure in the hoses over the ambient.

It seems like I could waste a gauge but then I would only be able to read pressure over ambient.

Was the testing done by DiveSports done dry, or in the ocean? Did you try it with other regs to see if it was only the Apeks that ended up with higher IPs?

(This does in fact hit back on an interesting (to me) point LuisH touched on. He suggested that a regulator could be test dove dry. But a chamber dive is not an ocean dive. It may tell you something about how a reg works, but it is hopefully not how APeks tested their dry environmental chamber design.)

I wonder if the 'over-balancing' was an intentional design, or an artifact of the design that was marketed as a feature.

Like Awap said, measuring the absolute pressure inside a hose is just the same as measuring the IP at any ambient pressure (at any depth) and just adding the known ambient pressure.

You probably have some specific reason to measure the absolute pressure, but the hose hoop stresses are governed by the differential pressure, not the absolute pressure. The absolute pressure doesnÃÕ really affect the structure on a hose, only the differential.



In the old days before they used to test regulators in the ocean, but you get much better test data when you can precisely control the environment. They can use wet chambers to test regulators properties that are affected by the water column.

Some things in nature are hard to replicate in a lab environment, but pressure and depth is not one of them. It is much easier to control the pressure and temperature in a chamber (even in a wet chamber or a chamber with a water compartment) than it is out in the ocean. You can also add a lot more instrumentations and take much more precise measurement when you can control the conditions.



As I have mentioned in other threads, IMHO, the 'over-balancing' (as defined by Apeks) is just a side effect of the dry environmental kit in a balanced diaphragm regulator.

Even if you size the outer and inner diaphragm at the exact same diameter, you will get this effect since the outer diaphragm is softer than the inner HP diaphragm. In essence the effective area of the inner diaphragm is reduce by its stiffness when it is combined with the clamping around the perimeter.

 

[PhilEllis]

Was the testing done by DiveSports done dry, or in the ocean? Did you try it with other regs to see if it was only the Apeks that ended up with higher IPs?

It was done in the ocean. I did also test an Apeks US4 first stage and a FSR first stage. The IP on the US4 remained constant, if I remember correctly. The FSR was the one that increased 10 psi.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

 

[beanojones]

It was done in the ocean. I did also test an Apeks US4 first stage and a FSR first stage. The IP on the US4 remained constant, if I remember correctly. The FSR was the one that increased 10 psi.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

So it seems that LuisH take that the over-balancing may be a side effect of the environmental kit may be what is happening.

 

[beanojones]

Like Awap said, measuring the absolute pressure inside a hose is just the same as measuring the IP at any ambient pressure (at any depth) and just adding the known ambient pressure.

You probably have some specific reason to measure the absolute pressure, but the hose hoop stresses are governed by the differential pressure, not the absolute pressure. The absolute pressure doesnÃÕ really affect the structure on a hose, only the differential.



In the old days before they used to test regulators in the ocean, but you get much better test data when you can precisely control the environment. They can use wet chambers to test regulators properties that are affected by the water column.

Some things in nature are hard to replicate in a lab environment, but pressure and depth is not one of them. It is much easier to control the pressure and temperature in a chamber (even in a wet chamber or a chamber with a water compartment) than it is out in the ocean. You can also add a lot more instrumentations and take much more precise measurement when you can control the conditions.

I have absolutely no reason for wanting to measure things, other than curiosity.

As far as chamber testing versus open water testing, it's one thing to know that the numbers are right, it's another thing for the thing to work in water. I am a big believer in the empirical. It's one thing to know things work at a particular pressure, it is another thing to know that it works in the ocean.

For me, nothing in a chamber is like anything in the ocean. And not just because you cannot wear underwear in the chamber. (I have worked as an inside tender FWIW.) I would never dive in the ocean at 3 ATA PO2, for instance.

(I have never dove a wet chamber.)

An interesting link:
Comfortable seating for underwater workouts