second stage - pressurize/depressurize

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hedonist222

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hi everyone

I purchased an apeks xl4+ as a backup spare tank regulator

I noticed immediately that it doesn't pressurize as vividly as my Scuba Pro S620 Ti.

Meaning when I turn on my spare tank (13 cf), it doesn't pressurize as spiritedly as my SP S620 Ti.
Same when I turn off the valve and de-pressurize.
It hisses the air out of the second stage for a good fifteen seconds.
Whereas my S620 Ti de-pressurizes in a second and very abrutply.

Same when I press the purge button on the apeks xl4+ second stage. No gust of air.

Is this normal?

I haven't dived with it yet.

I can post videos soon.
 

tbone1004

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@hedonist222 what is the first stage with your S620Ti? I assume it's a MK25. In that case the experience you are having is considered normal due to the design of the XL4 first stage.

If you are that interested we can go into the design parameters and engineering behind why they do that since they are upstream valve designs, the flow rates of the piston vs. the diaphragm itself, the potential of valve design differences between your 13cf and the full size tanks contributing to flow, etc etc. but that's a deep rabbit hole.

On the XL4+ second stage, the purge button is likely limited to a shorter throw than the S620Ti to prevent freeflow risk when you push the purge button.
 

rsingler

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Same when I press the purge button on the apeks xl4+ second stage. No gust of air.
How does it breathe when you suck in hard?
How does it breathe with a gentle small inspiration?
 

lexvil

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Sounds like the lever is to low on depressurization part
 

emoreira

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I guess that the behavior observed by the OP is due to the small orifice in the HP hose to the SPG.
If the HP hose has a very small orifice, it will inflate the HP hose internal volume and the SPG slowly. Furthermore if you close the tank and purge the second stage, it will also take some time to release the pressure inside the HP hose and SPG.
I've seen this in a brand of HP hoses where the orifice is so small that it takes time to presurize the system. This is, however desirable at some point, as it will preserve better the life of the spg and second stages, and in the case of a catastrophic failure of the HP hose, the tank will empty also slowly.
Some other HP hose brands this orifice is not so small, so, the pressure in the system rises more violently.
Manguera alta conector.jpg

I've also seen HP hoses where the orifice was so corroded that it hardly passed any air to the SPG.
 
OP
hedonist222

hedonist222

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@hedonist222 what is the first stage with your S620Ti? I assume it's a MK25. In that case the experience you are having is considered normal due to the design of the XL4 first stage.

If you are that interested we can go into the design parameters and engineering behind why they do that since they are upstream valve designs, the flow rates of the piston vs. the diaphragm itself, the potential of valve design differences between your 13cf and the full size tanks contributing to flow, etc etc. but that's a deep rabbit hole.

On the XL4+ second stage, the purge button is likely limited to a shorter throw than the S620Ti to prevent freeflow risk when you push the purge button.

Yes, mk 25 Evo.

Thanks for explaining.
 

lexvil

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So, more questions, do you have an SPG on the scubapro? How does the APEKS breath and same for the SP? What first stage on the SP?

as pointed out if there is a HP (SPG) hose on one and not the other this could easily be the slow bleed back from that hose = normal. If you do have an HP hose on both it may the more rapid flow of the bleed inherent in the first stage design or it maybe a designed limit to the purge of the APEKS second stage, I’m not hands on familiar with the XL.
 
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