Enviro sealed first stage with stable ip

[buddhasummer]

I have a project on the go, yes another.

I have some Conshelf 14 second stages and would like to pair them with an diaphragm enviro sealed first stage. Being an unbalanced second stage I'd like the first stage to be as stable as possible to ensure I can tune the second stage for best constant breathing without having to worry about free flowing either at depth or as tank pressure drops. It needs to be sealed as the water here gets pretty chilly in water, not to mention it's pretty dirty.

Apeks is obviously out due to its over balancing "feature". A MK11/17 swings up to 10psi.

I "fixed" the OB feature on my Apeks FSR by converting it to non sealed. Ip is stable but it's not sealed. My conshelf 14 first is the most stable with a 2psi swing, but again not sealed and has terrible hose routing if your using a drysuit. My SEA swings 6psi.

Is there a a non overbalanced, enviro sealed, diaphragm first stage currently on the market with a largely constant ip?

Or...

What increase in ip will a non balanced con 14 handle before going into free flow?

Happy to be corrected if my understanding is incorrect.

I really like the Con 14 seconds, simple, reliable, easy to service and breath well enough for my needs. I have mine cracking at around 1.1". Took them on a liveaboard with a converted DS4-US4 and was very happy with their performance. I like metal.

I'm trying to put together a super reliable, robust easy to service set for my fantasy year long remote diving safari. I can achieve this if the first stage is not sealed but not sure how to or with what if sealed.

Thanks for any corrections, advice or recommendations.

Cheers

 

[Centrals]

Leave out the Hydrostatic Transmitter of your "sealed" Apeks 1st stage.

 

[Pao]

IP blanking plug for DS4

I think you can make one, or just cutoff the "stalk" of the hydrostatic transmitter ;-) . Removing the hydrostatic transmitter might cause the environmental diaphragm to "cave in" at depth.

 

[buddhasummer]

Would that actually work? I don't understand enough about the physics to know. Presumably there is still pressure on the diaphragm, this would present no problem? Or negative effect? Cheers.

 

[buddhasummer]

IP blanking plug for DS4

I think you can make one, or just cutoff the "stalk" of the hydrostatic transmitter ;-) . Removing the hydrostatic transmitter might cause the environmental diaphragm to "cave in" at depth.

Interesting, I'll try to learn more about such a device. Cheers.

 

[Pao]

Would that actually work? I don't understand enough about the physics to know. Presumably there is still pressure on the diaphragm, this would present no problem? Or negative effect? Cheers.

The hydrostatic transmitter was used to replace fluid (usually silicone oil) which was quite messy during service time. Liquids are incomprehensible so they transmit pressure. The blanking plug will prevent the enviro diaphragm from compressing and should prevent the IP from rising. It takes a lot of pressure to raise the IP. Try pushing the diaphragm with an IP gauge attached

 

[buddhasummer]

Thank you. I will try such an experiment. I shoy off an email to N@90 enquiting. This could well be the solution I'm looking for. Nice.

 

[oldschoolto]

Just use the tried and true 14 supreme 1stage .....

Jim

 

[buddhasummer]

Just use the tried and true 14 supreme 1stage .....

Jim

Thanks Jim. Unfortunately a) I don't have one and B) the hose routing if using a DS is terrible.

 

[Pao]

Basically the transmitter adds to the mainspring pressure to resist the HP valve from opening. Increasing the spring pressure forces the reg to Increase its IP to "balance' this increased pressure. Without the hydrostatic transmitter spring pressure, and consequently IP, will be constant.