What's the small bit between the hose and the SPG for

[tbone1004]

@emoreira we are talking about different restriction points. The first stage and then the HP hose itself does all of the work, but the spool orifice size can't do anything as far downstream as it is. The dimension of that hole is a function of the size of the gauge port itself and what's left to work with once you put o-rings in there.

@BlueTrin if you have your regulators O2 cleaned, then I would use an O2 clean lube on those spool o-rings

 

[Akimbo]

I bought a SPG and a hose, the SPG came with a small insert which had two rings on each side to put inside the SPG and hose.
What is it for ?

This thread might help you understand the spool and dynamic O-rings. O-rings for Divers

 

[BlueTrin]

@emoreira we are talking about different restriction points. The first stage and then the HP hose itself does all of the work, but the spool orifice size can't do anything as far downstream as it is. The dimension of that hole is a function of the size of the gauge port itself and what's left to work with once you put o-rings in there.

@BlueTrin if you have your regulators O2 cleaned, then I would use an O2 clean lube on those spool o-rings

In general, should I put silicone on all parts with an o-ring ?

 

[tbone1004]

In general, should I put silicone on all parts with an o-ring ?

dynamic o-rings, yes, static o-rings no. Silicone only if you do not have your regs O2 cleaned, though on the LP side other than the first stage I use Dow111 silicone because it's better and the LP side doesn't really need to be O2 cleaned. So that would be the second stage o-rings, and the o-ring on the end of the regulator hoses. HP side gets O2 lube because my first stages have to stay O2 compatible for deco/IWR/CCR use.

@herman keeps reminding me that port plug o-rings are dynamic during install, however I do not typically lube those o-rings. If you take them out of the first stage, the lube causes them to attract all sorts of stuff and they are only momentarily dynamic. DIN o-rings are the same though only dynamic if you rotate the first stage while you're screwing it in and those should NOT be lubed. The important o-rings to lube are the regulator hose o-rings since those are regularly dynamic whenever you twist the regulators, and the SPG spool o-rings because those are twisted regularly as well. I lube mine if/when I remove the hoses, or annually, whichever comes first. Takes 3 minutes.

 

[emoreira]

@emoreira we are talking about different restriction points. The first stage and then the HP hose itself does all of the work, but the spool orifice size can't do anything as far downstream as it is. The dimension of that hole is a function of the size of the gauge port itself and what's left to work with once you put o-rings in there.

Now I agree, I think that the OP was refering to the small hole in the HP hose connector to the first stage. I was not refering to the size of the hole in the spool.

 

[Akimbo]

In general, should I put silicone on all parts with an o-ring ?

dynamic o-rings, yes, static o-rings no.

This is a risky suggestion which is inconsistent with recommendations by virtually all manufacturers, standards agencies, and industry in general. All O-rings should be properly lubricated because the O-ring moves in the groove (gland), even flat-face pressure seating applications. Granted, lubricating static O-rings is less critical than dynamic, but is still important to prevent damage during installation, premature failure, and small leaks. Note that many static seals are moving during the installation process even though the seating surfaces do not move under pressure.

There is a lot of folklore in recreational diving relating to the valve to cylinder connection. See: Scuba Cylinder Valve Installation, Post #40

Proper lubrication is important, especially in selecting compatible materials for the application. See: O-rings for Divers, 3: O-Ring Materials, Lubrication, and Maintenance. The safe material is not always silicon grease; both for media and O-ring compatibility.

 

[tbone1004]

@Akimbo I don't disagree and I lube them all during service with the exception of the valve outlet o-rings for both DIN and Yoke, and the tank-valve connection which the manufacturers recommend against. The difference is whether normal divers need to be doing it on o-rings they can see, and for that the only ones would be port plugs and hoses. I don't think the first stage side needs to be lubed under normal use, nor should they be exposed all that often. The lube put on them during service should be more than enough

 

[Sam Miller III]

Deleted

Too historical for the modern diver

 

[BlueTrin]

Now I agree, I think that the OP was refering to the small hole in the HP hose connector to the first stage. I was not refering to the size of the hole in the spool.

I was talking about the one you mentioned, but I appreciate both of your answers.

Just ordered some silicone lubricant.

Thanks guys.

So for clarification if I ordered some new hoses for my regulators, I should lubricate them too on both ends, but not excessively.

 

[Akimbo]

I don't disagree and I lube them all during service with the exception of the valve outlet o-rings for both DIN and Yoke, and the tank-valve connection which the manufacturers recommend against.

Which valve or cylinder manufacturer recommends against lubrication of the O-ring? I know that some distributors have but I haven't been able to find any manufacturers. XS-Scuba tech support does and Luxfer specifies lube (Dow Corning Compound 111) on threads and installing the valve per manufacturer's specs.

The major risk in installing cylinder to valve O-rings dry is damage during installation. It is less of an issue on Scuba cylinders because the duty cycle of that O-ring is normally only once before being removed and replaced -- they are usually pressurized after the valve is installed and are only bled down to zero when it is removed again. Here is the kind of damage that can occur when that O-ring is not lubricated.

This kind of damage is often incorrectly "assumed" to be from extrusion, but that would require gross overpressurization, improper material, and/or sizing. Techs at Parker Hannifin were confident that this damage was not caused by extrusion, even if the valve was inadequately torqued, because extruding this much material would exceed the point for catastrophic failure.