Long...MK10 plus ?

[buddhasummer]

read it as you wish, perhaps it is a result rather than a cause...

View attachment 404003

Interesting it has no SPEC boot groove..I guess cold water use was not a marketing strategy used.

 

[halocline]

1. The flat edge on the piston stem prevents the prior utilized knife edge from cutting right through the seat, allowing use with higher pressures.

The force pushing the piston into the seat is IP, and so higher tank pressures wouldn't make any difference. The MK15 is excellent with HP tanks and it uses a knife edge piston.

I think the text on the photo you posted that refers to the transition from the MK10 to the MK20 is a little misleading. (Who wrote that text, BTW?) There were two big changes from the early BP first stages to the later ones; rounded piston and the bushing system around the HP o-ring. The bushing system was typically touted as an advantage in HP applications because it tightened tolerances around the piston and prevented extrusion. But the MK10 plus was only a 'transition' in that it used the rounded piston. There are no bushings, so the HP o-ring arrangement is the same the MK10.

Also, I don't think that photo is of a MK10 plus; every one I've ever seen and every bit of SP literature on them shows the later model SPEC MK10s and the round yoke knob. The conversion kits came with a boot to replace the SPEC boot.

And the reference to '270 bars' is suspect as well; SP had a 232 bar DIN fitting that's mentioned in the MK10 plus manual, but I have never seen anything from SP that recommends 270 bar on a MK10 or MK 10 plus. Personally I would not use a MK10 or MK10 plus on a 4000 PSI tank.

I also see three years of revisions in my schematics, 96,97,98. So even the years in that photo appear to be not accurate.

 

[buddhasummer]

Yes, I believe that photo is of the plain Jane MK10.

 

[rhwestfall]

Without seeing the seat retainer, one wouldn't know....

 

[rhwestfall]

there was a question as to how it was being marketed, I think that the graphic shows that, seeing it is from the manufacturer.... inaccuracies and all...

 

[buddhasummer]

I don't know if it means anything but every schematic I've seen for a MK10 plus has the SPEC boot.

 

[Couv]

I use plain old camera O ring silicone grease when servicing my regs, I only dive 21%, should I be using Christolube or similar? Cheers.

Yes, plain old silicone is fine (up to 40% O2) unless you're using silicone o-rings which would absorb some of the grease and distort. In a bulletin, (#242) SP recommends a PTFE grease (Christolube) as it is a better lubricant. When using a PTFE grease in a piston first stage, you can expect a lower IP everything else being equal.

Now, just to muddle the waters a bit because I know you like it that way; when I say a "better lubricant" I'm not taking into consideration how long either will stay in place or how well either protects from corrosion-I think the jury is still out on those issues.

 

[NotSure]

I can see were going to the MK20 seat in the 10 plus would would reduce the chance of o-ring failure at the HP seat. It seems that all other regulators designed for higher pressures use bushings or a washer around the piston stem o-ring because that is the more likely failure point. With the MK10 and 10+ using the same body I can't see how the 4000psi claims can be true unless they found the the stem o-ring tolerances were good enough but the seat was a problem at higher pressures.

 

[halocline]

Without seeing the seat retainer, one wouldn't know....

You could be right, but for some reason I was thinking that the MK10 plus was a satin finish, and all the shiny ones with the matte finish seat retainer are MK10s that have been converted. But I'm not sure about it.

 

[buddhasummer]

I checked with a local SP dealer here and he confirmed what Halocline said above. He also said they weren't popular due to the price difference over the MK10. Who knows...