Difference between High Flow, High Pressure and Intermediate Pressure ports ?

[Nemrod]

Th so called High Flow ports may flow a bit more air, at wide open, as if you took a knife and cut the second stage hose in two and turned the air valve full on.

The restriction in flow occurs at the volcano orifice for a diaphragm first and at the piston knife edge for a piston regulator first.

The next restriction occurs at the knife edge at the second stage seat.

The hose, length of hose, diameter of hose, high flow or not (ports) are generally not a restriction of note at normal sport diving depths.

As some discover, time to time, another restriction is not turning your tank valve on partially or barely.

If a HF LP port had better routing I would use it, if a standard LP port had better routing, I would use it without guilt.

N

 

[socc]

Ok cool ! I get it.
Thanks all of you !

Another question I have, is what length a low pressure hose should be to connect with a the power inflator of BCD. I mean I suppose that depends, but what is the usual length ? I was looking to buy the Miflex Xtreme BCD Dry Suit Hoses | Simply Scuba UK but I do not know which is the right length for me ? I think that the 60cm might be the one but can please someone confirm.

Thanks,

Socc

 

[Agility]

use the length of hose that works best for you, it will not make any noticeable difference to the flow
some use 1.8m hoses (6ft) so called long hose configuration for their primary second stage and a very short one for their backup which they wear on a necklace under their chin, in an out of air (OOA) emergency they will give the OOA diver their primary second stage and take the one from the necklace for own use
others use a 60cm hose on their primary first stage and 90cm on their backup as they intend to donate the backup to a diver needing air under water


oh sorry, you were asking about the BCD hose.
you will have to adjust the length to the length of your corrugated hose, or if you use an airtrim BCD to the position of the connector.
best will be to set up the BCD with your regulator on a tank and measure. it should not be too long but too short is bad, too.

 

[halocline]

You might start with measuring the length of the corrugated BC hose, add 6-8" to that, and try to find a LP inflator how of that length. That's a bit of a rough guess. 60cm is about 24" and that seems about right for many BCs.

 

[knotical]

... but what is the usual length ? ...

Inflator hoses that come with pre-assembled reg sets are commonly 26 – 28 inches (66 – 71 cm). This might be a bit longer than you need, but too long is better than too short. The best way is to assemble everything and measure. While doing so, remember to vary the positioning of your BC on your cylinder, both up and down.

 

[socc]

Hello guys,

Thanks for your replies.

The reason I am asking is because I bought a regulator but I do not have a BCD and I do not think I will get one soon but instead I will rent one. So I was wondering what length hose should I buy to attach in my first stage. I am still confused to be honest one which length to choose to fit most of the BCDs.

Socc

 

[Agility]

so I went and measured some of mine, they are 60 to 70cm. As you intend to get a Miflex hose, I'd take 70 and a large rubber band you can slip over the corrugated hose to keep the inflatorhose in line with the corrugated hose. I have dived with a too short hose and it makes the positioning of the inflator uncomfortable.

 

[socc]

so I went and measured some of mine, they are 60 to 70cm. As you intend to get a Miflex hose, I'd take 70 and a large rubber band you can slip over the corrugated hose to keep the inflatorhose in line with the corrugated hose. I have dived with a too short hose and it makes the positioning of the inflator uncomfortable.

Ok thanks Agility. So should I go with the 71cm or 75cm (which might be an even safer choise). What do you think ?

Thanks,

Socc

Sent from my GT-I9505 using Tapatalk

 

[milbournosphere]

Not sure it's good marketing. Telling us one port is high flow implies the others are only mediocre.

I did a bit of searching when shopping for my regulator, as I was considering (and eventually bought) a Mk11 with *two* (a real value!) "high-flow" ports. Scubapro claims a 15% increase in air flow over their standard low-pressure port. I found a very good post by DA Aquamaster that's worth sharing:

...a high flow port means little as it is not the limiting factor in a regulator. For example, in terms of first stage performance a Scubapro Mk 2 will flow about 90 SCFm, a MK 17 flows about 177 SCFM, and a Mk 25 flow about 300 SCFM - but the highest flowing second stage available only flows about 65-70 SCFM. In that regard second stage flow is the limiting factor with a range fo performance from about 30 SCFM to 70 SCFM.

That said, at depth, a lower performing reg can start to lag due to excessive drop in intermediate pressure and it can in some circumstances become possible to over breathe a regulator where it begins to feel like it is not delivering enough gas to meet your instantaneous inhalation needs. But generally speaking with a high performance second stage and a first stage that flows at least 150 SCFM, it just isn't going to be an issue even in deep techncial diving.

If high flow ports do anything at all they create a bit more of a venturi effect in a diaphragm second stage and help the response time of the first stage a bit, but any difference noticeable at the second stage is minimal if the second stage has adequate performance.

And when I was renting my BC for a while, I used a 30" (76cm) hose. It fit a few different designs of BC with no problem.

 

[Agility]

You should be ok with 71cm as long as you do not use an Airtrim BCD.