Problem with my Proton XL

[kingabunyip]

I have a Mares Proton XL 1st stage and 2nd stage with a Mares axis octopus. I do quite a bit of below 10 deg C diving in UK quarry sites, so I had a cold water kit fitted by my local dive shop (Mares dealer), and at the same time had them serviced.
However, when I go below about 35 meters, the 2nd stage starts to free flow, slowly at first then full blown. I have tried taking it out of my mouth and holding it at various angles, but nothing I do seems to stop it. I sent it back twice for 'tweaking' and I was told nothing was wrong.
I asked Chris at Chepstow NDAC to have a look and he suggested that I put the Axis octopus reg onto the 2nd stage hose and blank off the octopus port, this would check if the problem was with the 1st stage. I had a great breath off it all the way down to 56 metres.
When I spoke to chris again, he'd had a look at my 2nd stage. He reckons that where the hose goes into the 2nd stage, there is a white plastic piece with a hex/allen key shape down the middle. He said its called a low pressure seating or knife edge or orifice. He told me it should have been changed on the service to a MK2 green one.
Is this right, and will it be the cause of the free flow?

 

[Greg Barlow]

I have a Mares Proton XL 1st stage and 2nd stage with a Mares axis octopus. I do quite a bit of below 10 deg C diving in UK quarry sites, so I had a cold water kit fitted by my local dive shop (Mares dealer), and at the same time had them serviced.
However, when I go below about 35 meters, the 2nd stage starts to free flow, slowly at first then full blown. I have tried taking it out of my mouth and holding it at various angles, but nothing I do seems to stop it. I sent it back twice for 'tweaking' and I was told nothing was wrong.
I asked Chris at Chepstow NDAC to have a look and he suggested that I put the Axis octopus reg onto the 2nd stage hose and blank off the octopus port, this would check if the problem was with the 1st stage. I had a great breath off it all the way down to 56 metres.
When I spoke to chris again, he'd had a look at my 2nd stage. He reckons that where the hose goes into the 2nd stage, there is a white plastic piece with a hex/allen key shape down the middle. He said its called a low pressure seating or knife edge or orifice. He told me it should have been changed on the service to a MK2 green one.
Is this right, and will it be the cause of the free flow?

Yes, a number of the original white LP orifice seats did develop some problems with leakage. Mares created a service kit to upgrade the Axis series. It contained the new, green seat and necessary O-ring. The seat was made green to make identification easier for the techs. While working for a dive center, I installed a significant number of the seats with the annual service.

That said, I have an early production Axis that still contains the original style seat. It has never had any problems, and has been used on deco/stage bottles for many years.

It is an easy fix on your reg, and should take the tech no longer than 15 minutes to complete the job. After the part is replaced, the second stage lever height will need to be adjusted for the proper cracking effort.

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

 

[Zak OHara]

Thanks for answering Greg. I've been travelling lately "tis the season".

Best regards,

 

[kingabunyip]

Thanks very much Greg. I'm armed and ready for the dive shop. They are normally good, so I can't see any problems.
Should the green one have come in the service kit or would it have been a special order part? I'm just wondering if they used an 'old kit'.

 

[redacted]

So what is the root cause of this problem? Gas bubbles in the seat material that are being compressed at depth and compromising the seal?

 

[Greg Barlow]

Thanks very much Greg. I'm armed and ready for the dive shop. They are normally good, so I can't see any problems.
Should the green one have come in the service kit or would it have been a special order part? I'm just wondering if they used an 'old kit'.

The hard seats are not normally installed with annual servicing. Normally, if a tech sees a white seat it is replaced with the newer, green version. Most Mares dealers do not charge for the part due to the known potential problem.

Greg

 

[Greg Barlow]

So what is the root cause of this problem? Gas bubbles in the seat material that are being compressed at depth and compromising the seal?

The problem lies with the hard, plastic seat; not the soft seat found on the LP poppet. The white seats were the first plastic seats used by Mares, as they always used plated brass seats prior to that time. Most manufacturers switched to the plastic versions a few years before Mares. The sharp edge on the seat was reconfigured on the new design. From what I have seen, the original design was more of a knife edge.

I have yet to see a green seat needing replacement, unless it was damaged from something other than normal wear-and-tear.

Greg