Intermediate Pressure

[Bambright]

For normal downstream second stage regulator, the intermediate pressure (IP) will be about 135-145 psi. And I heard that for upstream second stage regulator the IP will have to be around 170 psi.

Can any one explain why IP of upstream second stage regulator has to be higer than downstream regulator?

Thanks,

Bambright

 

[scubatoys]

In the olden days... Poseidon used to run very high IP... They don't anymore... and it's not necessary for an upstream design... they just happened to do it.

 

[ZenDiver]

In the olden days... Poseidon used to run very high IP... They don't anymore... and it's not necessary for an upstream design... they just happened to do it.

What he said....

 

[DA Aquamaster]

155 psi has been more the norm for the Poseiden regs I have seen. But their second stages also seem to do quite well around 140-145 psi when attached to a "normal" first stage.

The IP on a "normal" reg can be anywhere from 120-145 psi.

 

[pipedope]

And most hooka regulators run an IP of about 40 psi to reduce the load on the compressor.

 

[Bob3]

The Cyklon is a downstream design & still runs about 170 - 180, works OK lower.
The Jetstream/Odin & Xstream have a servo assist that's upstream & runs at 135 psi, still works at 125 psi.
Lots of bum info out there on the subject.

 

[Chad Carney]

Poseidon was always a unique line of regulators. Brilliant and obtuse all at once. Their IP on many models started out in the normal range and would climb as the tank pressure decreased, (a compensation principle.) They had overpressure valves in their second stage hoses.

Most mainstream regulators today run, as previously stated, at about 125 to 145 PSI.
Their most important factor is a solid lockup...that it not creep upward.

Chad

 

[rescuediver009]

The answer is there just note that this IP is only as the tank pressure is drained .. to about 300 psi I think. Therefore it breathes easier as the dives goes on. That is why they are setup at this pressure and may seem a little out of sort at the beginning of the dive. The servo assist valve is also something unique that plays a large role....

 

[Tim Wong]

Another question here. Would there be an effect on the IP pressure (and by how much) when air is drawn from the second stage? Thanks.

 

[ZenDiver]

Another question here. Would there be an effect on the IP pressure (and by how much) when air is drawn from the second stage? Thanks.

Can be from 15 to 30 psi drop on a breath....depends on regulator.