Seat and shims MK10 ?

[buddhasummer]

I often read people saying I set my ip at X,Y, Z, (piston regs) but almost never do they state at what tank pressure. Do they mean at 3000psi? Or 500psi? Depending whether they aim for high end of spec or low end of spec it could either, 135 for example. Just want to be sure. Thank you.

 

[redacted]

I aim for 130 at 3000 psi. I get between 125 and 135. At 500 psi, that often leaves be around 120 or a bit lower.

 

[buddhasummer]

Thank you, now I understand. Couldn't help myself, had some shims two different sizes .38 and .30, put in the .38 and at 3000psi ip sits just over 135, at 500psi it's sitting at just over 125. So the .38mm shim added around 6psi. Kind of tempted to try the.30mm shim but don't want to tempt fate. I think I'll leave it.

Edited with shim units of measurement for clarity.

 

[redacted]

Those numbers look good and still leAve room for wear.

 

[buddhasummer]

Thanks for the confirmation, I'll leave it alone and go diving.

 

[Couv]

Hi Buddhasummer,

Yes, when we say we "aim" for a particular IP we mean the maximum. Generally speaking that would be at high supply pressure in a piston, and low supply pressure in a diaphragm first stage. Of course the opposite end of must also fall within the specs. The maximum IP is also where the second stage is normally tuned.

Now, just for fun and to throw a little confusion into the mix, I think some piston regulators such as the MK20/25 have pistons with stems that have a flare on the hard seat end. This increase in diameter may cause an IP inversion like a diaphragm regulator. I don't have a fancy billion-piece-count-piston-first stage, so one of the rich kids like Halocline or Zung will have to confirm.

One point of clarification for others reading this thread. The shims mentioned in post #13 are 0.010 & 0.015 inches (~ 0.30mm & 0.38mm)

 

[buddhasummer]

Thanks for the clarification, I think I've got it all straight now. I left it sitting a while and it crept up a few psi, maybe 3-4, but hasn't moved since. I think I'll surivive a dive with it. Edited post 13. Measuring shims, I'm geeking out now, does that make me a real DIYer yet? Got a ways to go I think. Is it ok to play with shims without full service, like mid season if required?

 

[Couv]

You became a DIYer when you opened up your first regulator.

Yes, absolutely OK to remove/replace shims without a full service. The main thing to remember is to reinstall the hp seat and retainer in exactly the same position. Also, don't forget to re-lube the piston stem o-ring and piston stem.

You want some things real DIY geeky to do?
Next rebuild, remove the flash from the piston stem o-ring with a piece of emery cloth or sandpaper.
Try different lubricants and compare how they affect IP.
Remove the polished surface from the piston stem o-ring.
Micro-mesh the piston hard seat.

Have fun.

 

[buddhasummer]

You became a DIYer when you opened up your first regulator.

Yes, absolutely OK to remove/replace shims without a full service. The main thing to remember is to reinstall the hp seat and retainer in exactly the same position. Also, don't forget to re-lube the piston stem o-ring and piston stem.

You want some things real DIY geeky to do?
Next rebuild, remove the flash from the piston stem o-ring with a piece of emery cloth or sandpaper.
Try different lubricants and compare how they affect IP.
Remove the polished surface from the piston stem o-ring.
Micro-mesh the piston hard seat.

Have fun.

Thanks Robert, sounds like a challenge. Feeling more confident, I'll fully geek out on my next reg, a MK10 plus.

 

[Bryan@Vintage Double Hose]

One of the many great things about a MK10 is that once it's setup right you don't need to mess with it for a very very long time.