Question Skipping 1st stage Maintenance?

[CG43]

Hello Umuntu

Unfortunately, the types of liquids previously used in environmental chambers (alcohol or silicone oil) are not compatible with current O2 certification of regulators. AFAIK all diaphragm regulator manufacturers (except maybe Poseidon) have moved to dry sealed environmental chambers for Nitrox certification reasons.

And high proof Vodka used to work so well … especially after the day’s diving was done

Thanks for pointing out the oxygen certification.
This is actually a good reason not to use liquid.

However, I also use vodka in the recommended way.

 

[Pearlman]

In case I understand correctly [I keep misunderstanding ] (that you are asking in context of testing IP), yes
That’s how I do the overnight test, the HP hose will act as a „mini tank“ to utilize air from

Hmm, not so bad (how far below 9?) … What I remember testing the 25(not evo) is that on a full purge IP dropped sometimes to 110~105psi so… maybe maybe it’s normal

Yesterday night it on a hard breathing test it fell down to just below 9 when the lockup was at 9.3bar. Forgot to test full purge at the time as I was basically showing off to a lady friend at the time … Today it’s behaving more normal after I shut down and depressurised overnight to catch up on sleep. A full purge brings it down to exactly 9bar.

Connect everything (2nd, IP, spg, maybe even another downstream 2nd), maybe skip the inline tool to be sure …
then give it a quick look at ~[5,15,30,60m, 2,4,8hrs] (this is the steady state phase, so tinier variance happens here, more indicative of smaller leaks / imperfections that wouldn’t show up with a „bad creep“)

If you already have stable IP with, being charitable let’s say, nothing more than 5~10psi variance from initial lock up (transit phase), It’s pretty alright to dive; by the time you’ve breathed from that 1st, you are back into transient phase

Sure it will leak eventually if left pressurized long enough, unlike this legend of the quality of the mk5

Very interesting test idea! I tried this over a few hours with the valve shut off, removed the inline tool, and added the SPG. To begin with I found the tank pressure to be around 100 bar - so apart from the full purge test cycles that consumed the gas, there may the possibility of a slow leak as I left it open for almost 12 hours on day one. But since I never attached my SPG from the beginning I can’t be sure. Right now starting with 100 bar and with the tank valve off, the SPG dropped by 20 bar to read 80bar after 3-4 hours and the IP creeped up by just 5psi. 20 bar is 290 psi approx so where did it go? One possibility is general sloppiness in tightening the hose connections resulting in the slightest of leakages over extended hours… the odd thing here is that as soon as I depressurised and re-opened the valve again the SPG is back to 100 bar! So I am not really losing air yet the SPG dips by 20 bar over 4 hrs? How do I make sense of this??

All of my gear is comprised of balanced regs both 1st and 2nd stages, but If my tank drops to 600 psi I will check IP again. I am not spending $600on a supply pressure control - one tank is all I got.

The seat gets installed on the seat retainer, with an o-ring. Not in the space where you just installed the bushings.

Mostly correct. But the spring goes in first over the bushing and it surrounds the edge of piston stem and then you push-to-click against the spring action to install the seat.

All this info (or similar, I might not have all the details in the right order, I don’t work on MK25s very often) is in the service procedure manual, which is everywhere on the internet.

Yes I have the service manuals and schematics and following this video to the T :


This is really the best official looking demo of servicing the MK25 out there, systematic and using all the right tools compared to the many other maverick “this is how I do it with whatever tools I have” videos littered in the search results. The bushing installation step starts just after 09:00mins.

Removing the old HP piston o-ring/ bushing arrangement should be easy to do without using a sharp o-ring pick. I think you can push it out from the ambient side with a wooden dowel.

Oh! I did buy chopsticks for this and then clean forgot about them and kept trying with the brass pick but simply couldn’t hook it on the top edge no matter what … strange that even during the very first disassembly and the 2 rebuild attempts where I traced back my steps and re-installed the bushings to ensure I used the correct orientation and o-rings I kept struggling for up to 5 mins at a time to remove the inner most bushing (23) each time, whereas in the video above also all three (21,22,23) come out as a single unit at first attempt! At one time I needed a tea break to steady myself down and retry more gently with a calm mind. The sad results can be seen here:

 

[Mobulai]

A full purge brings it down to exactly 9bar.

Awesome!

ery interesting test idea! I tried this over a few hours with the valve shut off, removed the inline tool, and added the SPG. To begin with I found the tank pressure to be around 100 bar - so apart from the full purge test cycles that consumed the gas, there may the possibility of a slow leak as I left it open for almost 12 hours on day one. But since I never attached my SPG from the beginning I can’t be sure. Right now starting with 100 bar and with the tank valve off, the SPG dropped by 20 bar to read 80bar after 3-4 hours and the IP creeped up by just 5psi. 20 bar is 290 psi approx so where did it go? One possibility is general sloppiness in tightening the hose connections resulting in the slightest of leakages over extended hours… the odd thing here is that as soon as I depressurised and re-opened the valve again the SPG is back to 100 bar! So I am not really losing air yet the SPG dips by 20 bar over 4 hrs? How do I make sense of this??

Well.. having the spg attached and tank closed I have about 3-5 puffs (not lung but venting the 2nd) in there (maybe 2-3 full-ish breaths w lungs)

So before I check IP stability on the mk25, I like to watch the piston move to see how well it was lubricated (at the head) — since the 1st reason to check it was a whine; so I did quite a few venting cycles like that
Being to lazy to go get a fill, I was being savey with the amount of gas I used (it’s a small pony, actually a drysuit inflation tank that I got for testing)
Wish I had 750 to spare on that pressure controller valve tho

Basically I can get the piston to travel max range (min to max) like 4 (3.5 actually) times, with about 3 of them back to full IP, the 5th breath is where the reserve in the spg hose is fully depleted and the reg can be uncrewed

Losing bars from that is still not a good sign; if left alone without venting I get to keep (now at 120bar) reading on the spg through out the overnight test

Did you do a bubble test yet?

 

[Pearlman]

Basically I can get the piston to travel max range (min to max) like 4 (3.5 actually) times, with about 3 of them back to full IP, the 5th breath is where the reserve in the spg hose is fully depleted and the reg can be uncrewed

Not sure I understood … what do you mean 3 to get back to full IP when the tank valve is closed?

Losing bars from that is still not a good sign; if left alone without venting I get to keep (now at 120bar) reading on the spg through out the overnight test

Did you do a bubble test yet?

Not yet.. Will need a swimming pool for the bubble test right? Not sure where the SPG is loosing pressure when it goes back to a full 100 bars upon opening the valve again…

 

[halocline]

I’m still having a little trouble following your conversation, but maybe this is useful:
1. To test IP at different supply pressures with one full tank, start with testing it at full, then close the tank valve and simply tap the purge to bring supply pressure down to where you want.
2. If you are attempting to test active IP drop under demand with a typical IP gauge, it will not be accurate. I’ve talked about this in several older posts. You would need a flow meter or something that is designed to measure pressure while air is moving.
3. If you pressurize a regulator, turn the tank valve off, and the pressure drops, even very slowly, it means you have a leak. The easiest way to find it is to fill up a tub and submerge the task/regulator, and be patient. Eventually you’ll see a bubble.

 

[Mobulai]

Not sure I understood … what do you mean 3 to get back to full IP when the tank valve is closed?

Tough to film it with one hand (should invest some time in building the bench)
This is another mk20 (upgraded), so tougher to see the piston through the ambient holes, but you can still see the spring move; you can see in the 2nd run (almost)3 times I purge and the IP gets back to „spec“

If you’re losing bars without any venting/purging then you have a leak — do what Halocline suggested, easiet way to find it

I’m still having a little trouble following your conversation

It’s a special noob language we share (I certainly identify as a noob)

 

[Pearlman]

I’m still having a little trouble following your conversation, but maybe this is useful:
1. To test IP at different supply pressures with one full tank, start with testing it at full, then close the tank valve and simply tap the purge to bring supply pressure down to where you want.
2. If you are attempting to test active IP drop under demand with a typical IP gauge, it will not be accurate. I’ve talked about this in several older posts. You would need a flow meter or something that is designed to measure pressure while air is moving.
3. If you pressurize a regulator, turn the tank valve off, and the pressure drops, even very slowly, it means you have a leak. The easiest way to find it is to fill up a tub and submerge the task/regulator, and be patient. Eventually you’ll see a bubble.

Ok let me try - It’s not the IP guage that is dropping IP, It’s the SPG to measure tank pressure that appeared to drop 20 bar over 4 hours when the valve was closed. IP remained constant. Then mysteriously after reopening the valve the SPG was back to 100 bar tank pressure. So I am wondering what’s happening on the SPG for it to drop when no air was consumed…

 

[Mobulai]

Then mysteriously after reopening the valve the SPG was back to 100 bar tank pressure

This is the no mystery, tank has always been at 100bar pf tank volume (much bigger than the hose volume, even on pony size)

The tank is not part of the equation when valve is closed

What leaked the 20bar of hose volume?
bubbles are the way to find out

 

[Pearlman]

This is the no mystery, tank has always been at 100bar pf tank volume (much bigger than the hose volume, even on pony size)

What leaked the 20bar of hose volume?
bubbles are the way to find out

Yeah but if tank pressure really leaked then the new pressure upon opening the valve should have been 80 bar. But nothing was lost, so would there really be any bubbles? Anyways I am testing again to confirm … will check 4 hrs later …

 

[Mobulai]

let’s assume a 12l tank; when you purge your 2nd (with tank valve open) 4-5 times at 200 bar; how many bars do you end up with?
Probably still gonna read 200

When you closed the valve and left it for 4hrs; your „tank“ in taht case is only the hose of the spg — like what, 50-100mL vs a whole tank?

The spg is reading pressure from the reg not straight from the tank

The video I uploaded shows that.. when you purge on a closed valve it’s only 2-3 puffs of air to go to 0bar