mk20 seat retainer torque

[dinogep]

i have acquired a pair of used mk20 -s. After servicing them I have set the IP by adding shims between the regulator body and the seat retainer. The torque specified (both in the service manual and on the back of the seat retainer) is 15 Nm, however at his torque the shims that were supplied with the service kit deform, and significantly extrude from the gap between the seat retainer and the body. Is this normal, or the shims I got are softer than the original ones?

 

[redacted]

I have seen that spec on some schematics at 30 Nm (266 in-lb) 15 Nm is the lighter spec you will find. I suspect the problem is slipping that 2nd washer under the retainer to raise IP. I suggest you move the washers inside to the spring where they belong. I will remove the retainer washer entirely if I just need to drop the IP another 5 psi but have never tried more than 1 washer. OTOH, that connection should hold just fine with a lettle less than 15 Nm torque so if you can get close I would expect it should be OK. As that new seat takes a set, you may well want to remove one of those washers to bring IP back down a bit.

 

[dinogep]

Thanks for the advice. I have also seen that 30Nm on the MK20 TIS diagram on scubaproregulatormuseum.org, but I thought it was a misplaced label, since the 15Nm (actually 15-17) is engraved into the retainer itself...

 

[Zung]

The schematic is wrong, and the value engraved in the seat retainer is correct.

I also torque my MK20's to 15 Nm/133 in-lb/11 ft-lb, and the shim(s) don't extrude. My shims also come with the service kits; I have 2 kind: the white ones and the slightly thicker black ones.

One reason I can think of is I usually hit any threads with a tiny bit of grease to avoid seizure, and the grease may get on the shim; maybe that helps with extrusion, or maybe not.

 

[dinogep]

Interestingly, I have discovered, that in the box where I threw the shims from the old MK20's there are two types, a slightly more and a slightly less transparent one. If I remember right, the more transparent extruded, the less transparent did not.