I can't think of any way to be honest.

I have a cheap and not particularly nice IP gauge that plugs into a BC-style inflate hose. Nice and easy

 

IP pressure setting

Bought 2nd hand reg off ebay, seller says he has dialled down the intermediate pressure on the 1st stage.

OK, I'm going to have it serviced anyway, but am curious. I know how to adjust the IP (cubapro Mk25), but don't know how one knows when it is at right IP...?

Anyway to know without buying and IP gauge?

Ta,

Dave

Makers preset the IP for a reason and it isn't wise to try and alter it. When you have the reg serviced the tech will check and re-set the IP to manufacturers spec.

Phil

 

Makers preset the IP for a reason and it isn't wise to try and alter it. When you have the reg serviced the tech will check and re-set the IP to manufacturers spec.

Phil

In general, I'd go along with that, but I'd also point out that several manufacturers have an acceptable range for IP rather than a fixed value.

Also, a small minority of people (e.g. mCCR rebreather divers) need to adjust the IP as this regulates the rate of flow of O2 into the rebreather.

David

 

think deep deep guys use to adjust the ip settings for depth,

tweeking!

i use apeks with helium mix at depth they work smashing,

not sure if its adjusted with shims or allen bolt,

bung it in for a service, he should check the ip after rebuild me thinks,

 

The IP on a Mk25 is only adjustable by around + or - 1 bar via the Allen screw on the end, so it's only for fine-tuning. To adjust by any more you'll need to add or remove shims which means dismantling the first stage.

The IP on an Apeks reg can be adjusted over a very wide range. I've reduced the IP on the Apeks US4 that I use for suit inflation to around 5 Bar in order to reduce the flow.

 

The IP on an Apeks reg can be adjusted over a very wide range. I've reduced the IP on the Apeks US4 that I use for suit inflation to around 5 Bar in order to reduce the flow.

by adjusting to 5bar - I assume 6ATA - does that mean you can't get gas in your suit past 50m?

 

Anyway to know without buying and IP gauge?

IIRC they are only about £10.

Where are you based, you're welcome to borrow mine.

Juz

 

I seem to recall that Draeger do a reg with a very high IP, don't know if it is depth compensated or not though.

Poseidon 1st stages are designed to run at high IP's as well, sealing them is a bit more complex but it's been done. Tubby, the Aussie homebuilder, did a step by step on how to do it.

I think a simpler solution is just either getting rid of the KISS valve or blocking the orifice to make it just a bypass and plumbing a needle valve in with an unmodified 1st stage.

Cheers,

Stuart

 

The D5 sidemount rebreathers that Dr Duncan makes use a standard 1st stage (the word you are looking for is compensated, Mark, not balanced) then it's run through a Swagelok needle valve. As you head deeper you wind down the needle valve so it's letting less of the denser O2 through (but the same number of O2 molecules). Rick Stanton has had one down to 180m using a Poseidon 300 1st stage and a needle valve.

If you want to remove the compensation on a DS 4 you unscrew the cap and cut the stem off the pressure transmitting thingy. Or fit a delrin cap. Either way, it stops the water pressure from pushing on the spring and increasing the IP. Standard industrial regulators like you find on welding sets work like this- they have no compensation and instead have simply a spring and diaphragm.

If you want a stiffer spring to wind up the IP, you can get them from Kato Entex. They'll make any old crap, any size and any spring rate.

I believe the IP on an inspo only affects the time the solenoid fires- a higher IP means you get more O2 through on each squirt so the solenoid fires less frequently. Lower the IP and you get more bangs but less each time so it's probalby more controllable. I think they use standard compensated 1st stages. On a KISS the flow is directly proportional to the IP as it's going through a teeny orifice.

 

Thats very usefull thanks.

Seeing as i know F/all about springs is there any guidance you can give me as to what to ask for?

Id like an IP of arround 15max. The present DS4 strugles past 13


ATB

Mark

 

Apparently Paul at Revo has some stiffer DS4 springs. Drop him a line.

 

So what difference is there between balanced and unbalanced, and does that affect what happens differently on a diaphragm/piston design?

Also, I'm sure I read somewhere that environmental seals were dangerous for deeper diving. Mark Ellyatt's literature I'm sure. Is this true, and why?

Finally, I thought all regulators were depth compensated. That is clearly wrong. Why on earth would you want a reg that wasn't compensated?

Sorry for the digression here.

 

As I understand it the main danger was they wernt sponsering him


Its not the regulator thats compensated its the first stage (the bit that goes on the tank) and you want a non depth regulated one to make a KISS or other MCCR work as it should.

ATB

Mark

 

There is a considerable difference between balanced 1st stages and balanced second stages.
The term balanced can often be confused for "adjusted".
Some first stages, such as Sherwood's, "adjust" for the drop in cylinder pressure as the gas is used.
This is to compensate for the fact that when the cylinder has 3,000psi in it, it will be exerting a greater pressure on the piston face (which is a given surface area) than when the cylinder only has 300 psi in it.
The first stage spring is approx. 120 psi, this, plus the 20 psi from a full cylinder, (3,000 psi) exerted on the "flow by" piston face, = approx. 140 psi.

On for instance, the same Sherwood valve, as the pressure in the cylinder drops, so the "knife edge" that seals against the piston seat moves away from the piston (again, which is a given surface area), thus assiting the spring as now there is only 1 psi linear force exerted on the piston by the gas.

In addition to this "adjusting" diving regulators then need to stay a certain pressure ahead of ambient pressure.
Apeks suggests an interstage pressure of between 9 and 10 bar, say 9.5 bar, this is then kept at 9.5 bar above ambient as you go deeper or shallower, so your valve allways gives you 9.5 bar over bottom pressure.

There are various reasons why manufacturers suggest and use a particular interstage pressure, such as trying to reduce the cooling caused by gas expansion, longevity of seat materials, i.e. reliability, ease of manufacture etc.
There used to be a Norweagian valve manufacturer that had a philosophy of having very low, 7 bar I.P. to help reduce the effects of cooling, i cannot remember the exact name, but they worked well. Likewise some Posiedons have a high 12 + I.P. and there valves work well too.(usually !)
All the manufacturers belive thier method is the way forward, so i would give a great deal of thought before i changed a valve i breath off, as oppossed to used for say, an argon cylinder.

I think the AP oxygen valve IP is not so much concering the volume of gas, but more the force exerted on the solinoid valve, and not having to great an IP pressure causing it iether to jam open, or more likely, not open at all !

Now a balanced second stage is a different animal ....................