mk17 S600 adjustment

[HeatCker]

hope i can describe this so that it makes sense..
i have a SP mk17 1st stage..
i have an S600 2nd stage..
i adjusted the orifice so that the 600 free flows (hisses slightly) when wide open..
i did this adjustment on a full tank 3400 psi..
just for the heck of it i hooked up my regs to a tank with 600 psi..
the free flow is much much greater at 600 psi then when hooked up to the 3400 psi tank..
i went back and forth, same happened every time..
why is that ???

 

[grantctobin]

The MK17 is not completely balanced. The IP rises a few psi as cylinder pressure drops. Expected behavior. If you’re going to tune your own regs, I’d recommend at the very least reading the first stage service manual.

 

[207diver]

With a MK17 or MK11 the IP will be higher with a lower supply pressure. In my experience it is generally around 10 psi difference. By the book both should still fall somewhere between 125-145 psi. I typically adjust A MK17 to 140 with a 500 psi tank and it ends up around 130 at 3000 psi.

 

[Couv]

What they said ^^^ The important takeaway is to adjust the second stage to the highest IP. Some regulators (like your MK17) have a higher IP at low supply pressure. Time to invest in an IP gauge.

 

[HeatCker]

thanks for the explanation(s)

 

[buddhasummer]

A MK17 can swing as much and even a tad more than 15psi full to 500psi. As others have said tune your second stage when tank is at low pressure not full.