Scubapro chrome plated brass regulators...

[Open Ocean Diver]

Received the gate valve today and wow is it ever feather light to open and close. Waiting for the other pieces to plumb into my upright vacuum.

 

[Open Ocean Diver]

Let's review:
The Intermediate Pressure (IP) is the pressure available at the second stage. (It also closes the first stage valve-but that is not relevant here.)

The second stage does not care about the tank pressure-only that it receives usable and steady IP. Some first stages have greater IP at lower tank pressure-some have greater IP at higher tank pressure. If I'm going to sell a second stage separate from a first stage, I tune it to an IP of 135 psi as that splits the usual tolerances. If I'm selling a second stage with a first stage, I adjust the cracking effort when the IP from the first stage is at it's greatest pressure.

Cracking Effort is altogether different. Cracking effort is the amount of pressure differential it takes to open the second stage demand valve. This pressure differential is usually measured in inches of water. Put simply, it is the amount of vacuum inside the second stage case applied when the demand valve opens. We only observe the IP drop as an indication of when both the first stage and second stage demand valves open.

The second stage may not care about supply pressure, but the first stage sure does and guess who supplies IP to the second stage.

Review:
Quote from Pete Wolfinger... balanced first stages... The primary purpose of balancing is to eliminate or reduce the variance is intermediate pressure produced by the diminishing supply pressure. Depending on 1st stage design it will go up or down. He goes on to say the first stage responds to supply pressure and the second stage responds to intermediate pressure. If the IP is stable and predictable throughout the supply pressure range the adjustment of the second stage can be done more accurately. If a variance in IP exists, adjustment of the second stage must allow for the change in intermediate pressure.

 

[Couv]

If a variance in IP exists, adjustment of the second stage must allow for the change in intermediate pressure.

Which is why the second stage is tuned to the highest IP the first stage will supply over the range of tank pressure. For instance let's say your first stage has IP inversion. If you tune the second stage at full tank pressure, you'll have unwanted freeflow as the tank pressure decreases.

 

[Open Ocean Diver]

Which is why the second stage is tuned to the highest IP the first stage will supply over the range of tank pressure. For instance let's say your first stage has IP inversion. If you tune the second stage at full tank pressure, you'll have unwanted freeflow as the tank pressure decreases.

Sometimes it’s hard to pick the brains of the well-equipped, but I persist... Thank you

just what I was looking for.

Now please... definition - IP inversion?

 

[James79]

Sometimes it’s hard to pick the brains of the well-equipped, but I persist... Thank you

just what I was looking for.

Now please... definition - IP inversion?

Some first stage designs have an IP increase as the tank pressure drops (DA Aquamaster double hose is like that... I don't know which single hoses do) an unbalanced diaphragm reg will be that way.
Respectfully
James

 

[Couv]

Some first stage designs have an IP increase as the tank pressure drops (DA Aquamaster double hose is like that... I don't know which single hoses do) an unbalanced diaphragm reg will be that way.
Respectfully
James

What he said. ^^

I think the ScubaPro MK25-because of the flared piston knife edge and the MK17-because of the environmental cap diaphragm have IP inversion.

 

[Open Ocean Diver]

What he said. ^^

I think the ScubaPro MK25-because of the flared piston knife edge and the MK17-because of the environmental cap diaphragm have IP inversion.

Thanks

 

[Andrew Dawson]

This any help to those looking for the tiny screw for the regulator covers:

Store | Vintage Double Hose

These are for the SP 108 and 109s....but...is the 4x40 size, not metric.

 

[Open Ocean Diver]

This any help to those looking for the tiny screw for the regulator covers:

Store | Vintage Double Hose

These are for the SP 108 and 109s....but...is the 4x40 size, not metric.

I believe mine are metric based on thread pitch. Thanks

 

[Open Ocean Diver]

Oscillation is back. Check it out... Now I can repeat it.

https://share.icloud.com/photos/05STf4-6edQ8nIA1DoRttAnXg#Downtown_Toronto