Scubapro Mk10 - low intermediate pressure

[Enraptured of the Deep]

Is not 125 at the bottom edge of Scubapro specs?

I

Sure, an IP of 125 is within spec, but the 119 IP at 300 psi supply pressure is below spec. I will add that fourth shim, maybe even tomorrow, and see if that brings the IP within spec at both 300 and 3000 supply pressures.

 

[Rusty Shackleford]

Is not the spec at 3,000?

 

[Couv]

Is not the spec at 3,000?

IP must be checked at low and high tank pressure and remain within the 135 +/- 10 psi.

 

[lexvil]

If I remember correctly, I once received a MK 10 that had chronic low and irrational LP, it had been rebuilt with silicone lube, I opened it up, wiped it out and re-lubed with tribolube and it suddenly had 135 IP and was rock solid.

 

[Enraptured of the Deep]

If I remember correctly, I once received a MK 10 that had chronic low and irrational LP, it had been rebuilt with silicone lube, I opened it up, wiped it out and re-lubed with tribolube and it suddenly had 135 IP and was rock solid.

That is very interesting. I have some tribolube and can certainly give it a try.

 

[Bigbella]

Is there any chance I have the shims arrayed incorrectly? I have seen a number of posts on this forum suggesting it is best to have at least one shim at each end of the spring (if more than one shim is needed), but the Scubapro technical literature shows all three shims in a Mk10 at the end of the spring near the knife edge.

If I recall correctly -- dependent upon the model -- upwards of six of the SP stock .3 mm shims were allowed, up to three in each location -- under the spring and under the end plug. Each shim raises the IP by about .3 bar (about 5 psi).

Older models only allowed for three, under the spring . . .

 

[Enraptured of the Deep]

I tried tribolube in place of silicone grease on the piston and dynamic piston o ring, per suggestion from @lexvil . No improvement in the low IP at 300 psi suppy pressure.

Next, I added a shim, specifically a 0.010" one. That means I have four shims in the Mk10, three 0.015" shims and one 0.010" shim. I also wiped off the tribolube and reapplied silicone grease.

Success -- a steady 125 psi IP at 300 psi of supply pressure! I will need a fresh tank before I can confirm the new IP at 3,000 psi supply pressure, but I expect it will be within spec.

Thanks to all for your advice in this latest early adventure in DIY regulator servicing.

 

[Couv]

I tried tribolube in place of silicone grease on the piston and dynamic piston o ring, per suggestion from @lexvil . No improvement in the low IP at 300 psi suppy pressure.

Next, I added a shim, specifically a 0.010" one. That means I have four shims in the Mk10, three 0.015" shims and one 0.010" shim. I also wiped off the tribolube and reapplied silicone grease.

Success -- a steady 125 psi IP at 300 psi of supply pressure! I will need a fresh tank before I can confirm the new IP at 3,000 psi supply pressure, but I expect it will be within spec.

Thanks to all for your advice in this latest early adventure in DIY regulator servicing.

Excellent news.

Thank you for the update. It's post like these detailing each step I find most informative.

 

[rsingler]

My experience is I have seen IP increase after service but never the reverse.

Which makes sense for a piston, yes?
As the knife edge digs into the seat, the piston extends a few thousandths further into the HP chamber than when the seat was new. This compresses the piston spring just a touch more, requiring a higher IP to seal.
Good observation!

 

[Rusty Shackleford]

Exactly, it’s taking a set. Parts are wearing together.