Slow Mk V IP recovery

[Boiler_81]

I just rebuilt my Mk V. The IP recovery is slow compared to my Mk VI. Both regulators are on the same tank. I used the same IP gage and the same 109 converted to BA for the purge. Any suggestions?

Mk V Dropbox - Mk V.mp4
Mk VI Dropbox - Mk VI.mp4

 

[redacted]

I can not see your attachments. But I would start by removing the filter and see what that does (after making sure tank valve is fully open).

 

[Couv]

Have you cycled the MK5 at least 30 times?
Has the MK6 been in use longer than the MK5 since rebuild?
Did you use the exact same type of kit for both rebuilds particularly the same seat?
Is the piston hard seat nice and sharp?

BTW if my sense of timing is correct, it seems like the MK5 is recovering in about 4 seconds-nothing that would concern me.

 

[Boiler_81]

The Mk VI has not been rebuilt by me. I have no idea when it was last gone through. I was just using it as a reference since it and the Mk V are the same internally.

Have you cycled the MK5 at least 30 times?
Has the MK6 been in use longer than the MK5 since rebuild?
Did you use the exact same type of kit for both rebuilds particularly the same seat?
Is the piston hard seat nice and sharp?

BTW if my sense of timing is correct, it seems like the MK5 is recovering in about 4 seconds-nothing that would concern me.

 

[Bryan@Vintage Double Hose]

I wouldn't drawn any conclusions about the first stage IP reading till I'd done 200 to 300 cycles. Tapping a 2nd stage is not the best way to seat either stage in my opinion.

 

[halocline]

I watched your video, I wouldn't be too happy if a MK5 that I had just rebuilt locked up that slowly. Here are a few guesses as to why, and I really do mean guesses. 1) Friction at the HP o-ring caused by either a too-low durometer o-ring, poor lubrication at the o-ring, maybe some glazing on the piston shaft. 2) Very slight imperfection on the piston edge. Use a jeweler's loupe to inspect the edge and make sure there are no tiny scratches or nicks. If there are, either a) get a new piston b) clean up the edge with some sort of abrasive, or c) live with it. 3) A bad seat, or a seat with a pre-existing groove cut it in, which happens if you pressurize the reg even once and then take the seat out and re-install.

If you know that you used a 70 or 75 duro o-ring for the HP piston spot, there's your problem and you need to replace it with a 85 duro EPDM (that's OEM) or better yet a 90 duro EPDM, viton, or polyurethane. If you are reasonably sure that you used the correct o-ring and enough lube in that spot, just live with it, pressurize it for several hours to make sure it doesn't creep any higher, and go on a dive or two. I bet it then it will be fine.

 

[Boiler_81]

Thanks for the thoughts. All of the O-rings are from a kit I purchased several years ago from Vintage Double Hose. I assume they are correct. I will dive with it and then check the lock up again. If it continues to be slow, I will tear it down again and check the points you have suggested.

I watched your video, I wouldn't be too happy if a MK5 that I had just rebuilt locked up that slowly. Here are a few guesses as to why, and I really do mean guesses. 1) Friction at the HP o-ring caused by either a too-low durometer o-ring, poor lubrication at the o-ring, maybe some glazing on the piston shaft. 2) Very slight imperfection on the piston edge. Use a jeweler's loupe to inspect the edge and make sure there are no tiny scratches or nicks. If there are, either a) get a new piston b) clean up the edge with some sort of abrasive, or c) live with it. 3) A bad seat, or a seat with a pre-existing groove cut it in, which happens if you pressurize the reg even once and then take the seat out and re-install.

If you know that you used a 70 or 75 duro o-ring for the HP piston spot, there's your problem and you need to replace it with a 85 duro EPDM (that's OEM) or better yet a 90 duro EPDM, viton, or polyurethane. If you are reasonably sure that you used the correct o-ring and enough lube in that spot, just live with it, pressurize it for several hours to make sure it doesn't creep any higher, and go on a dive or two. I bet it then it will be fine.

 

[redacted]

Some Mk20/25 kit contain more than one 2-010 o-rings but only one is duro 85/90.

 

[buddhasummer]

Some Mk20/25 kit contain more than one 2-010 o-rings but only one is duro 85/90.

Is there an easy way to tell? Or just by feel? With the 85/90 being noticbly harder? Cheers.

 

[halocline]

Yes, the higher duro o-rings are noticeably stiffer. The SP ones tend to have a stripe as well. The 70 duro 010s are for LP port plugs.