SPG spool leak; did I service it incorrectly?

[Lorenzoid]

So, when I noticed small bubbles leaking from the connection between my SPG and hose, I knew it was the so-called "spool." Reading through the various threads in which someone asked about this, the solution seemed simple: unscrew the SPG, pull out the spool, and either replace the o-rings or replace whole thing. I replaced the spool with one from Dive Gear Express, and figured that was that. I coated the o-rings lightly with Tribolube. Perhaps too lightly? I didn't want to accidentally get lube into the spool orifice. I tightened the connection just beyond hand tight using two adjustable wrenches. I pressurized the reg set and put the SPG in a bucket of water to test it out, and observed no bubbles. However, on the first actual dive, I was getting bubbles--even more bubbles than before I replaced the spool. What did I do wrong? I had a dive shop fix it, but I didn't have the opportunity to ask a tech what the problem was.

Can anyone point me to an illustration that shows in cutaway view how this connection works? It seems to me that only one of the o-rings is captured in the swivel connection, while the o-ring at the other end remains fixed. I'm pretty good at mechanical things, but I just can't seem to visualize how this mechanism serves to provide an airtight swivel connection.

 

[Scared Silly]

Did you clean the hose and SPG? That area is prone to lots of corrosion and mineral deposits. As such, the spool might not have had a chance to properly seal.

The spool is not fixed but floats between the hose and SPG. The hose and SPG when screwed together merely holds the spool in place.

 

[uncfnp]

Silly question on my part but did you use the correct spool? I know of three different spools available.

Otherwise sounds like you did everything right. For spool o-rings I use a fair amount of lube. You don't want it to happen but my understanding is that if a little lube gets into the SPG it does no harm.

 

[gopbroek]

The DGX style of spool uses a flange in the center to prevent it from traveling to far in either direction, into the hose or the receiver coupling. This style will fit most applications and to the best of my knowledge as long as the hose end bottoms out on the coupling thread without actually bottoming out on the flange it should be correct. When tight, W/O pressure the SPG should rotate freely on the hose. If it does not rotate freely then you probably need a 'bullet' style of spool W/O a flange.
As Scared Silly stated the threaded portion of this coupling is mechanical only and provides no seal. The seal is provided by the orings and the inner walls of both the hose and SPG must be clean and free of any srcatches, corrosion or deposits or else you will have small leaks. The lube is for ease of assembly but does not provide a seal.

 

[cerich]

So, when I noticed small bubbles leaking from the connection between my SPG and hose, I knew it was the so-called "spool." Reading through the various threads in which someone asked about this, the solution seemed simple: unscrew the SPG, pull out the spool, and either replace the o-rings or replace whole thing. I replaced the spool with one from Dive Gear Express, and figured that was that. I coated the o-rings lightly with Tribolube. Perhaps too lightly? I didn't want to accidentally get lube into the spool orifice. I tightened the connection just beyond hand tight using two adjustable wrenches. I pressurized the reg set and put the SPG in a bucket of water to test it out, and observed no bubbles. However, on the first actual dive, I was getting bubbles--even more bubbles than before I replaced the spool. What did I do wrong? I had a dive shop fix it, but I didn't have the opportunity to ask a tech what the problem was.

Can anyone point me to an illustration that shows in cutaway view how this connection works? It seems to me that only one of the o-rings is captured in the swivel connection, while the o-ring at the other end remains fixed. I'm pretty good at mechanical things, but I just can't seem to visualize how this mechanism serves to provide an airtight swivel connection.

what brand is your spg?

 

[Lorenzoid]

what brand is your spg?

No brand name, but probably this: White Face Premium SPG, Naked | Dive Gear Express®

The replacement spool appeared to be identical to the one I removed--the style with with the center flange or shoulder.

Did you clean the hose and SPG? That area is prone to lots of corrosion and mineral deposits. As such, the spool might not have had a chance to properly seal.

The external threads on the SPG and internal threads on the HP hose fitting looked clean to me. Maybe I missed something on the interior of the hose fitting, past the threads? Is there a technique for cleaning the HP hose fitting? The orifice in the SPG doesn't appear to be cleanable--I mean, it's just a smooth bore into which one end of the spool fits, right? There did not appear to be any corrosion whatsoever on the spool, and the o-rings looked fine, but as I said, I replaced the whole thing anyway.

For spool o-rings I use a fair amount of lube. You don't want it to happen but my understanding is that if a little lube gets into the SPG it does no harm.

Yeah, since it's a swivel seal one would think lube should be generous, but comments on previous threads about replacing a spool suggested only light lube. So I lubed lightly.

 

[fmerkel]

Too late now if you took it to a shop. I'd first check for corrosion issues in the hose and gauge. I've had new spools leak as you describe (generally not), and simply putting in a different one took care of the problem. When O-rings get that small I wonder how accurate the tolerances are, not to mention the bore you put them in to. You are sealing up to 3500psi+ which is a lot for an O-ring. They need to be 90 durometer (harder), not 70 for a spool. I'm sure DGX is aware of that but they didn't put it together. It could have been assembled wrong at the origin.

 

[redacted]

All spools are not the same. So, one downside of replacing the entire spool rather than just the o-rings is that the o-rings may have to find a new sealing surface. If there are deposits on that surface, the seal may be compromised.

BTW, I load those o-ring and the threads with lots of lube. The lube will not damage the SPG.

 

[fmerkel]

All spools are not the same. So, one downside of replacing the entire spool rather than just the o-rings is that the o-rings may have to find a new sealing surface. If there are deposits on that surface, the seal may be compromised.

BTW, I load those o-ring and the threads with lots of lube. The lube will not damage the SPG.

That makes sense, hadn't thought about that issue. This is another of those situations when I wish the industry would just standardize. No need for 3 different style of spools.
I also tend to be generous with lube for this application, though I do attempt to not glop it over the hole.

 

[Scared Silly]

The external threads on the SPG and internal threads on the HP hose fitting looked clean to me. Maybe I missed something on the interior of the hose fitting, past the threads? Is there a technique for cleaning the HP hose fitting? The orifice in the SPG doesn't appear to be cleanable--I mean, it's just a smooth bore into which one end of the spool fits, right? There did not appear to be any corrosion whatsoever on the spool, and the o-rings looked fine, but as I said, I replaced the whole thing anyway.

It is not the threads that make any difference but internal bore where the spool is located. One can clean them by placing the hose in a solution of vinegar and water and using pipe cleaner in the bore. You can do the same with the SPG. You just want to keep them facing down so that the cleaning solution does not get into the small orifice via capillary action. Make sure they are completely dry afterwards.