Dolphin valve seal problem

oxyhacker · 27th July 2007, 15:16

I have a US (Luxfer aluminum) Dolphin tank I bought used a while ago. When I tried to fill it just now, it started leaking vigorously around the valve bonnet nut and shaft. I pulled the valve apart, expecting to see a bad O-ring, but they are both fine. What's odd, is I can find no trace of any seal between the bonnet nut (what the english instructions call a cap screw, that is to say, the big threaded plug with a hole in the middle for the valve spindle that screws into the valve body) and the valve body.

The manuals and schematics I have all show a bonnet nut with a large overhanging hex on the top and a groove for an O-ring underneath it. My bonnet nut has a small hex at the top and no provision for an O-ring at top or bottom. The only thing I can think of it that it had a crush seal at the bottom of the hole which got left out and some point, and the thing was sealing by inteference fit alone.

Can anyone tell me which, or point me to a schematic of the US valve?

oxyhacker · 27th July 2007, 15:57

Hmmm....

After staring at it for a while, I began to wonder if Draeger might really not have used a seal - one the valve spindle is in there is hardly any room for one. Put it back together, and it seems to work fine. Seems oddly Undraegerish, since the slightest loosening and it will leak.

Bosh · 27th July 2007, 16:40

I have a similar/same problem.

When its fully open or closed it seals well.

I am strongly considering cylinders with a normal DIN fitting, and modifying the Dräeger firststage to normal DIN aswell. Using an adapter is also an option, if not wanting to modify the firststage.

Best regards

Bo

oxyhacker · 28th July 2007, 11:42

Martin at Tecme sent me the right schematic for my valve, and it appears that there is indeed NO seal between the valve bonnet and the valve body, and it relies on metal-to-metal!

The schematic shows something there, which collectively with several other components is called a seal, but examining the real item shows it is clearly a anti-friction washer between the valve spindle and the bonnet nut and not a seal, as does a close look at the schematic.

Seems very odd in this day and age to use a metal to metal seal, since if it gets the slightest bit loose it will start - as mine did - to leak.

27th July 2007, 15:16	#1 (permalink)
oxyhacker New Member Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: Feb 2006 Location: NE USA Posts: 14	Dolphin valve seal problem I have a US (Luxfer aluminum) Dolphin tank I bought used a while ago. When I tried to fill it just now, it started leaking vigorously around the valve bonnet nut and shaft. I pulled the valve apart, expecting to see a bad O-ring, but they are both fine. What's odd, is I can find no trace of any seal between the bonnet nut (what the english instructions call a cap screw, that is to say, the big threaded plug with a hole in the middle for the valve spindle that screws into the valve body) and the valve body. The manuals and schematics I have all show a bonnet nut with a large overhanging hex on the top and a groove for an O-ring underneath it. My bonnet nut has a small hex at the top and no provision for an O-ring at top or bottom. The only thing I can think of it that it had a crush seal at the bottom of the hole which got left out and some point, and the thing was sealing by inteference fit alone. Can anyone tell me which, or point me to a schematic of the US valve?
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27th July 2007, 15:57	#2 (permalink)
oxyhacker New Member Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: Feb 2006 Location: NE USA Posts: 14	Re: Dolphin valve seal problem Hmmm.... After staring at it for a while, I began to wonder if Draeger might really not have used a seal - one the valve spindle is in there is hardly any room for one. Put it back together, and it seems to work fine. Seems oddly Undraegerish, since the slightest loosening and it will leak.
(Offline)

27th July 2007, 16:40	#3 (permalink)
Bosh New Member Current Rebreather/s: Dolphin Other Rebreather/s: Not Bought Yet Dolphin Join Date: Dec 2006 Location: Denmark Posts: 40	Re: Dolphin valve seal problem I have a similar/same problem. When its fully open or closed it seals well. I am strongly considering cylinders with a normal DIN fitting, and modifying the Dräeger firststage to normal DIN aswell. Using an adapter is also an option, if not wanting to modify the firststage. Best regards Bo
(Offline)

28th July 2007, 11:42	#4 (permalink)
oxyhacker New Member Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: Feb 2006 Location: NE USA Posts: 14	Re: Dolphin valve seal problem Martin at Tecme sent me the right schematic for my valve, and it appears that there is indeed NO seal between the valve bonnet and the valve body, and it relies on metal-to-metal! The schematic shows something there, which collectively with several other components is called a seal, but examining the real item shows it is clearly a anti-friction washer between the valve spindle and the bonnet nut and not a seal, as does a close look at the schematic. Seems very odd in this day and age to use a metal to metal seal, since if it gets the slightest bit loose it will start - as mine did - to leak.
(Offline)

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