Mares MR12 IP Differences

[supergaijin]

I have a problem reg... Mares MR12. Balanced 1st stage diaphragm.

On a full tank, the 1st stage has an audible leak from the LP side, main spring.... sometimes. Then the IP swings dramatically higher. My thinking is the diaphraphm is not seating properly, allowing air to pass by, causing IP to increase in an effort to close the seat.

On an 'empty' tank, the IP locks up at the recommended IP. No worries.

I thought that balanced 1sts do not/ should not have major IP differences. Can someone tell me what I'm missing here?

 

[herman]

Your right, the IP should be very stable.
I am assuming this is a later (longer straight MR-12 as opposed to the original flat design). First, make sure where the air is coming from. If air is coming from the spring chamber and not a LP port, then you either have a defective diaphgram or it is improperly sealing for some reason. Has it been serviced lately? If so, then I would look for diaphgram seat damage, an incorrect or damaged diaphgram, a loose retainer or an improperly installed diaphgram.

 

[supergaijin]

Reg was purchased new as part of our rentals. Approx 30? dives on it thus far.

When testing I have all ports plugged except for the IP guage threaded on to the DFC port (normally used for the primary), and its 2nd stage as a pressure relief.

My first impression was that the IP swing was normal due to the hard seat taking a set, but then when I checked it on a tank with approx 70 bar, the IP was solid. I was hoping not to have to open the whole thing up with my limited tools here- not even a vice

Thanks Herman.

 

[Fishpie]

If the 1st stage is leaking (externally) the only place it can do so is from the spring housing which would indicate that the diaphragm is not sealing.
It either has a hole or more likely the retainer hasn't been tightened down enough.
Tools needed to service the MR12 are very minimal.
IP gauge
12" adjustable
10mm allen key
Circlip pliers
Pick

NOTE.....the MR12 doesn't have a washer between the spring housing and diaphragm.

....from what you describe I'd go straight for the spring end, remove the spring housing, check the diaphragm, screw the housing back onto the diaphragm (firmly) and reset IP.

 

[herman]

I would first check to make sure the diaphgram retainer is tight. Although not my first choice, you can check to see it's tight with an adjustable wrench(spanner), if that is all you have, it will have to do. It should be plenty snugg but don't go overboard with it. If that does not fix the problem then a bad diaphgram is likely. The best way to remove them is with all the LP ports blocked except one and the retainer removed, shoot LP air in to the open port to blow the diaphgram out. If it is cut or just will not come out that way, CAREFULLY cut an X in the center of the diaphgram with a razor and slip a curved pick into the hole to pull the up one of the edges of the X then grab it with needle nose pliers. There is a metal button under the diaphgram, try not to knick it but if you do, just polish off any rough edges, a scratch on it is not a big deal. Trying to dig the diaphgram out by the edge with a pick is a sure fire way to damage the seating surface and pretty much distroy the reg....which is why I ask if it had been sericed lately.

---------- Post added February 1st, 2013 at 08:20 AM ----------

Looks like Fishpie was typing while I was.
If you are not familure with the MR-12, it is almost identical to the Conshelf.

 

[Joe Bailey]

Actually it might not be the diaphragm. It very well may be a damaged seat or an improprly installed orrifice, wich will ruin the seat eventually. I'd check out the high pressure side first.

 

[Nemrod]

I would think a bad orifice or seat or possibly the balance chamber seal.

N

 

[supergaijin]

I am still waiting on some tools to arrive so that I can disassemble the reg. Thanks for all your suggestions.

 

[herman]

I would think a bad orifice or seat or possibly the balance chamber seal.

N

Actually it might not be the diaphragm. It very well may be a damaged seat or an improprly installed orrifice, wich will ruin the seat eventually. I'd check out the high pressure side first.

Normally I would agree but in this case since he has an obvious (audiable) air leak in the spring chamber area then that has to be corrected first. Bads springs and/or trash in that area can give you some strange problems like IP jumping all over the place.