mk17 IP

[gfaith]

Be sure and have a 2nd stage hooked up to the 1st stage when you are adjusting it. Easiest way to purge it when testing too.

 

[WantSomeScuba?]

Depends on what definition you are using when referring to over balanced, with Apeks "over balancing" refers to a increase in ip as depth increases, on a MK17 the ip increases as tank pressure drops, which SP refer to as"ip inversion". Happy to be corrected if my understanding is wrong cheers.

No, you're right. I was over-simplifying.

On a MK17 if the ip increases from 500pi to 3000psi this would be indicative of a problem. One would expect the ip to decrease, according to SP literature, by 5-10 (?) psi. It should only swing one way, no?

Also correct. You know what you're talking about.

 

[halocline]

I thought over balance IP increase happened at deep depths in response to ambient pressure, not supply pressure.

I believe it refers to ambient pressure and tank pressure.

I think it refers to whatever the manufacturers want to sell that day. For the fine engineers who realized the ambient seal diaphragm happens to be larger than the internal diaphragm, "overbalanced" means increased IP with depth increase beyond the change in ambient pressure. For the fine manufacturers passing off a partially unbalanced upstream valve in a diaphragm 1st stage as something new and great, it's tank pressure.

Either way I would take with a large grain of salt. A first stage's job is to provide absolutely stable IP regardless of the situation; that's what allows for the best tuning of a 2nd stage.