Can I Reuse this Diaphragm?

[sdavo]

I am overhauling a Dacor 900 first stage, and I have been unable to find a source for a suitable new diaphragm. None of the diaphragms in the Trident catalog have the correct dimensions. Can the diaphragm pictured here be reused? It is still soft and pliable. Can the high pressure seat pictured be reused, or should I replace it?

 

[Jonny Wishbone]

Fold the diaphragm in half and roll it back and forth in several directions and flip it over and do the same. if there are no cracks in the rubber when you roll it then it will still work. Some say that you can't reuse a diaphragm because you can't get it crushed back in right but I have been using several Dacors with the same diaphragms for years. I only have a couple that I had to make a new one for. when you put it back in make sure you crush it in pretty snug under the smooth side of the SS ring. I have been diving Dacors since the mid 80's and love them. If you want to replace the diaphragm you will need to cut it out yourself from a small sheet of EPDM fabric renforced rubber material. The EPDM material can be purchased at McMaster-Carr. Just trace the old one and cut out with scissors. There is room for some forgivness past the diaphragm seat ridge so don't worry about perfection as long as it is slightly bigger and not slightly smaller...As far as the HP seat goes, you need to check IP and see if there is any IP creep in pressure. If you want to replace the HP seat you can get the Trident one from Northeast Scuba Supply or "resurface" the one you have. To resurface take 600 grit wet paper and a bit of dish soap. put the seat face down on the wet paper on your kitchen counter and work it in a figure 8 pattern then turn it a bit and do it again, each a few times until you have a new flat surface (its kinda like having your rotors turned on a brake job). The face of the HP seat responds very well to this and I have never had to do one twice. Just make sure the cone surface that seals against the HP seat does not have any pits, nicks or damage. It is this cone that seals into the seat face..... keep us posted...

 

[sdavo]

Thanks for the thorough reply! I'll inspect the diaphragm and resurface the high pressure seat as you described.

Is fabric reinforced EPDM the standard first stage diaphragm material? Would that have been the original diaphragm material in this Dacor 900? McMaster lists a number of other fabric reinforced rubber sheets (SBR, neoprene, silicone, etc.) in addition to EPDM.

The service literature I have for this regulator specifies an original diaphragm thickness of 0.110" - would the 1/16" thick sheet be an appropriate thickness for making a new diaphragm?

 

[Jonny Wishbone]

Yes the EPDM will be a bit thicker than the original but it works perfectly. Some older Dacors came with diaphragms that were 1/8 inch thick. If you get the EPDM get the 1/16" thick.

 

[sdavo]

I meant to type 1/8" in my last post - my reg has the thick diaphragm. It looks like I'll need the thick material to get sufficient clamping force on the diaphragm.

 

[Jonny Wishbone]

The 1/16 will work fine. It will still crush in as it should. The old diaphragms that were thick were not fabfic renforced so they had to be thicker.

 

[Brilig]

Hi sdavo, Jonny Wishbone gave me a lot of good advice on rebuilding my Dacor 950 and Dacor 360 and I have a bit of information to add from my experience. My 950 had the thick 1/8 diaphagm and I tried to rebuild it using the 1/16 EDPM but I couldn't get it to work. I would thread the pieces together but even all the way screwed down it wasn't tight enough to hold.
I ended up using two pieces of the 1/16 glued together with rubber contact cement and it works great. I just dove with that regulator yesterday.
If McMaster-Carr makes the EDPM in 1/8 and you don't mind buying a sheet then that's the way to go. But if you're trying to keep your expenses down I thought I would pass along this information.

 

[Brilig]

I should also add, do give the 1/16 a try. It may work just fine in your Dacor 900. I just wanted to relate my experience with my 950 in case you ran in to the same difficulty I had. My 360 definitely used the 1/16.
I'm just a beginner at working on regulators so keep us posted on your progress.