Pressing Question

[tauchmieze]

Student was asking about different reg pressures, and I wanted to confirm what the correct/best answer is.

If the first stage converts high pressure to intermediate pressure, and the second stage converts to ambient pressure like I learned in my PADI materials, then what's with the low pressure hose between the first and second stages?

Another instructor barged in and stated there is really only high and low pressure, but that seems oversimplified?

Appreciate some clarification from you techies.

 

[herman]

IP..
I have seen it called mid pressure as well but bottom line is, the first stage converts tank pressure (aka high pressure) to around 140 psi (10sih bar) that is distributed into all of the LP ports and any hoses connected to them. Any second stage drops the IP in the hose to ambient pressure..I suppose the confusion is calling the port/hoses low pressure but at the same time, refering to the the actual pressure in the hose as IP.

 

[Hickdive]

1st stage reduces the pressure to about 8-10 bar above ambient, second stage reduces to ambient. Because the hose connects the two stage reduction in pressure it is known as the "intermediate" pressure hose.

All the other "low" pressure hoses coming from the 1st stage are also pressurised to about 8-10 bar above ambient but there is no second stage reduction to ambient; gas from those hoses arrives in the BCD or drysuit inflator at 8-10 bar above ambient. Thus there isn't a two stage reduction in pressure therefore there is no "intermediate" stage.

However, this is basically semantics as both the BCD and regulator hose are at 8-10 bar above ambient and therefore, in scuba terms, "low pressure" hoses. The only difference between them is that the regulator one has a fitting at one end that screws into a second stage and the BCD one connects to a BCD or drysuit inflator nipple with a quick-release fitting.