Is this MR22 HP cone right?

[spoolin01]

I posted a longer version over on DIY, but just crickets so far.

I've got a Mares MR22 that went into free flow with little warning. The seat looks like it fractured. The cone has some scarring across the seating edge that more or less seems to match up with the damaged spots on the seat. I don't know if those are both symptoms of some event, or if a damaged cone stressed the seat. The reg went >200 dives after being rebuilt by a LDS.

I read on the internet that the MR22 cone is the same as that in many of the Aqualung regs. I had just serviced two Titans in the days before opening up the MR22 and indeed they look the same to me. Except that the Titan cones had sharp edges and the one in the MR22 is rounded and seems polished at the crown. Is this normal wear? Original design? Sloppy triage?

I'll probably buy the Mares kit for converting to the trimaterial seat, but as a general matter I'm interested to know about these original parts.

Here's a pic of the cone and seat.

 

[scubafanatic]

....I'd ask this question over on the MARES forum......either the MARES rep 'Zak' or Greg Barlow will be able to answer your questions.

 

[Fishpie]

The seat material on the older seats (like the one in the picture) are notorious for doing exactly what is shown.
They are a poor design that is made worse by getting salt water inside. They were supposed to last 2 years, but rarely did.
The new tri-material seats are a huge improvement and may even be as good (better) as the AquaLung seat.

 

[LeadTurn_SD]

I posted a longer version over on DIY, but just crickets so far.

I've got a Mares MR22 that went into free flow with little warning. The seat looks like it fractured. The cone has some scarring across the seating edge that more or less seems to match up with the damaged spots on the seat. I don't know if those are both symptoms of some event, or if a damaged cone stressed the seat. The reg went >200 dives after being rebuilt by a LDS.

I read on the internet that the MR22 cone is the same as that in many of the Aqualung regs. I had just serviced two Titans in the days before opening up the MR22 and indeed they look the same to me. Except that the Titan cones had sharp edges and the one in the MR22 is rounded and seems polished at the crown. Is this normal wear? Original design? Sloppy triage?

I'll probably buy the Mares kit for converting to the trimaterial seat, but as a general matter I'm interested to know about these original parts.

Here's a pic of the cone and seat.

Hi spoolin01,

If you are still reading this: Fishpie's reply nailed it. Get the upgrade kit with the "Trimaterial" poppet. I put the upgrade kit in a couple Mares regs now (MR22, MR12) and it seems great so far.

Out of curiosity, do you know the history of the reg? The reason I ask is that the HP seat appears like it may have been exposed to salt water at some point in its history.... the last one I rebuilt, although very well-used, was shiney and perfectly clean; the one you have picture appears discolored/spotted. If salt water did get into the 1st stage, that would have probably accelerated the break-down of the seating surfaces as Fishpie mentioned.

Best wishes.

 

[spoolin01]

Thanks for the recommendations on the trimaterial kit, that seems like a good upgrade. I bought the reg used and had it serviced after using it a bit. I didn't know anything about regs at that time, so I didn't pay much attention to the used parts that were returned. The cone does look like maybe it had been cleaned of corrosion at some point doesn't it, but when I opened it myself again after 200 dives, it was pretty clean inside, at least compared to my Titan of similar use and maintenance history. The thing that struck me was how rounded the orofice is, compared to those in my Titans (which look identical). Considering the scarring across the orifice, I was wondering if someone had damaged the orifice - maybe while trying to remove it - and then polished it down, or whether the older cone/seat combinations - if the seat material was that brittle - had been designed with less aggressive edges.

 

[LeadTurn_SD]

Thanks for the recommendations on the trimaterial kit, that seems like a good upgrade. I bought the reg used and had it serviced after using it a bit. I didn't know anything about regs at that time, so I didn't pay much attention to the used parts that were returned. The cone does look like maybe it had been cleaned of corrosion at some point doesn't it, but when I opened it myself again after 200 dives, it was pretty clean inside, at least compared to my Titan of similar use and maintenance history. The thing that struck me was how rounded the orofice is, compared to those in my Titans (which look identical). Considering the scarring across the orifice, I was wondering if someone had damaged the orifice - maybe while trying to remove it - and then polished it down, or whether the older cone/seat combinations - if the seat material was that brittle - had been designed with less aggressive edges.

Hi spoolin01,

The orifice on the new seat appears to be the same as the old one, as far as I can tell (rounded/beveled). I'm looking at a new Trimaterial upgrade kit as I type this, and it looks just like the one you have in the picture, just shiney and polished ...I'll be rebuilding my personal MR-22 this weekend, so I just happened to have the upgrade kit to refer to...

It could indeed be that the last person who serviced the reg tried to pry the seat out with an o-ring pick rather than gently blow it out with compressed air. The sealing-edge could have been scratched.... but I sort of doubt a tech would be that clumsy and my money is still on water intrusion due to accidently leaving a dust cap off and dunking the reg, then using it that way for numerous dives.... but who knows?

At any rate, putting in the new poppet and seat should make it "good as new", and with some luck you'll have a nice dependable reg for many years.

Best wishes.

 

[Greg Barlow]

From the looks of the parts, I would say that your reg did get a dose of sea water at some point. The corrosion on the hard seat is indicative of such a problem.

Mares experimented with many different soft seat materials over a period of years. They marked each design with a particular symbol to aid in research on finding a method to control the "chipping" that you can see in your photograph. Many of the failed seats displayed the same characteristics as your reg. They also used various hard seat edge configurations to determine whether a sharp, knife edge works better than a slightly radiused design.

Scubapro did the same type of work with their balanced piston designs. They used sharp edged pistons along with those with a rounded edge. Each particular design has its strengths and weaknesses.

The tri-material seats have proven to be excellent. They typically will last in excess of 150-200 dives, and display very little intermediate pressure creep.

Considering that your reg made more than 200 dives prior to needing service is pretty impressive.

Greg Barlow
Former Science Editor for Rodale's Scuba Diving Magazine