Creeping intermediate pressure

[Joris]

I think it is more like quickly locking up somewhere between 140 and 145 psi, then easing up to somewhere between 145 and 150, but the gauge is in bar, I don't remember exactly, and I can't check now.

 

[Interceptor121]

What changes when you go from fresh to salt?

If the issue is the sealing of the HP seat it does behave differently in fresh and salt

But this is only guessing. You have done the right thing taking the regulator into service and if you have a spare take it with you for additional safety
The IP setting will not fix the creeping that only influence the opening and closing but if the seat is not sealing it WILL creep

 

[fppf]

IP creep is when the pressure keeps going up and up until one of the second stages starts leaking or popping. If it just slowly increase a few PSI and then locks up and stops thats really not a creep per say.

 

[Joris]

Ah, OK, I didn't realise that.

 

[redacted]

I look at creep as any increase after the initial recovery. A recovery to 130psi and then a slow increase over the next 15 seconds to 135 is creep. There is a little sloppiness somewhere'\; the seat, the knife edge, or even the HP o-ring. While I don't see that much as a problem that needs correction, it is a symptom of a problem that should be expected to get worse. If the IP creep is taking IP over the specified max (145) it really needs to be delt with as it is either already causing a freeflow somewhere or will be soon. I like to set my IP in the low part of the 125 to 145 range, typically less than 130. And then I do something about it when it get to 140.

I suggest you at least have then adjust the IP to 135 or less.

 

[fppf]

This is coming from the aerospace industry.
But what you are describing is called "lock up" pressure. In a regulator, when it stops flowing and needs to seal the source off, it takes some force to seal it. As the seat wears, it will take more and more force to seal the seat and stop the pressure from increasing. You are very correct, this is indicating that the seat is starting to wear. Its just the terminology used.

 

[Scared Silly]

There is also the scenario that after replacing a seat that it takes it a bit to settle. I just replaced a HP and cycled the reg a bit and there 5-10psi creep. Once it hits 145psi it locks up. I figured that after a few dives it will lock up at and hold after the initial recovery. Some shops will run the regs through a bunch of cycles on a machine which will accomplish the same thing. Unfortunately, not everyone is so lucky to have such a bench.

 

[fppf]

Its recommended you put at least 100 cycles on the first stage and 50 cycles on the second stages. So if you cycle each second it will give you 100 on the first. A cycle is as simple as hitting the purge button. Does not need to be at any set rate. Just keep hitting the purge.

 

[redacted]

It only takes a minute or 2 to get that many cycles by hand. Hold the pressurized 2nd in one hand and tap the purge button with a finger from the other hand. Each tap will flow a bit of gas. That will go a long ways toward setting the HP seat and a quick test of new parts.

 

[Ed Palma]

I onced serviced a Beuchat VX100 whose symptom was free flowing after leaving it pressurised for some time. My friend kept diving it because breathing from it relieved the problem. However, one time when he was at depth, the free flow became continuous, Apparently, the O-ring between the high pressure and intermediate pressure zones extruded. I'll post a photo as soon as I can.

Point of this story is that as Awap pointed out earlier, a possible cause for creep could be the HP O-ring. I guess the difference would be the rate of creep. The way the OP describes the creep, it does seem to be a HP seat problem, but I would really bring a spare along just in case.

At any rate, creep or no creep, I think a 50-dive trip would warrant back-ups for most things