Calling AWAP et Al: MK20UL + SP HP Qick-Disconnect?

[mahjong]

And a special shout out to DAaquamaster as well!

Might anyone know if it is okay or not to use the old Scubapro HP quick-disconnect system, the one that attaches directly to the first-stage (not to the spg or computer), with an MK20 Ultra Light? Maybe it's a non-issue, but I do recall reading some warnings about being careful with the resin-coated aluminum (is it aluminum?) of the UL. Just wondering if anyone has any thoughts or experience.

I have used this HP quick disconnect for years with my MK10 and love it. I have a brand new one and would use this one with my MK20UL (packing for travel right now), so corrosion is not an issue.

Thank you!

 

[Zung]

I have no direct experience with it, but I have a similar case that's the other way around: I took an extra DIN MK20 for an experiment during my last dive trip. I also took an UL DIN-Yoke adapter. I did 3-4 dives over 2 days with this setup, rinsed it well after each dive, then move back to my standard rig. After the trip, the threads in the aluminium adapter is corroded. Still usable, but with clear corrosion marks.

It might not have happened if I removed the adapter after each dive. The problem with you rig is if it happens, it'll affect your regulator instead of an expendable (if somewhat pricy) adapter.

OTOH, one might say corrosion is a problem no matter what, because standard hoses have fittings made of brass.

 

[redacted]

I have never heard of any caution and the QD connection to the MK20UL is no different than a standard hose connection. Hopefully DA will be along soon.

 

[Zung]

The problem is between the aluminum body of the MK20 UL and the brass fittings: galvanic corrosion will happen. See wikipedia or MIL-STD-889B.

 

[redacted]

The problem is between the aluminum body of the MK20 UL and the brass fittings: galvanic corrosion will happen. See wikipedia or MIL-STD-889B.

I agree. But it is the same problem you could have with a hose connection (also chrome plated brass). I'm not sure how that is managed, but whatever works for one should work for the other.

 

[Zung]

Aye Aye Master, that's what I said.

... OTOH, one might say corrosion is a problem no matter what, because standard hoses have fittings made of brass.

I wonder if originally there's any UL-approved sort of fittings, stainless steel maybe?

 

[BlueWaterDiving]

ScubaPro used to put the little black and gray ring in the repair kits for the UL so that the brass fittings did not touch the reg. If you can find them they work good.

 

[DA Aquamaster]

The plastic rings were intended for the Mk 20UL and I guess they work but all they really do is provide a barier between the brass and aluminum on the outer surface of the reg. That makes sense to a degree given the expsorue to salt water, etc.

However, you still have the issue with the brass threads on the fitting being in contact with the aluminum threads in the reg body. However that is not any different than what you have with a chrome plated brass tank valve in an aluminum tank.

The preventative maintence is the same in each case - a very thin coat of christolube (or silicone) to help reduce the corrosion and to prevent the aluminum threads from getting galled.

What I have found when servicing several MK 20ULs is that the chrome plated brass hoses seem to do well with that treatment. I've actually had bigger issues with the port plugs - if they are not also lubricated and removed at least annually, they can get severely stuck.

So, the QD fitting won't create any more issues than a chrome plated brass hose fitting.

One thing I have noted with that particular QD fitting is that if it comes partially unscrewed, it has a sweet spot where it can disconnect but still trap the gas in the SPG. The end result is that your SPG reading no longer changes and will read the same, creating the potential for a OOG event if you fail to note the non-changing reading. So when you use it, snug it up tight to prevent the normal movement of the spg and hose from causing it to unscrew part way.