Brass Vs Nylon Orifices for 2nd stages

[AquaNSun]

Brass/metallic orifices Vs Nylon orifices (for 2nd stages) - which is better and would brass offers more precise adjustments and noticeable improvements over Nylon? Do 1st stages also come with both brass and Nylon orifices?

 

[muddiver]

Brass is optimum for use with gas mixes with higher O2 concentrations. There will be a big debate over the cut off, but the CGA and most regulator manufacturers will say anything over 40% O2 requires oxygen compatable parts.

I dive Poseidon regulators and the first stages are oxygen compatable because they use metal valve seats and bushings. The valve is a ball type seat so the valve oriface does not wear from the seat pressing aginst it.

As far as the second stage side of the regulator, the pressure is too low to be an issue with oxygen. Nylon will give a better seal at the valve seat with less spring pressure and you only have to replace the nylon seat when you service the regulator. With a matallic seat you may have to replace or machine the the orafice, depending on the design of the valve.

 

[AquaNSun]

This is interesting. Do you have a diagram showing your Poseidon first stage metal valve seat and orifice configuration? I'm trying to imagine your descriptions.

 

[halocline]

Nylon will give a better seal at the valve seat with less spring pressure and you only have to replace the nylon seat when you service the regulator. With a matallic seat you may have to replace or machine the the orafice, depending on the design of the valve.

Sorry, but this is totally false, assuming you're talking about typical 2nd stages. A brass (or SS) orifice does have a better edge, usually, than the plastic ones, and will seat more precisely against the EPDM or neoprene seats. Unless there is some damage, you never replace the orifice, just the soft seat.

The newer SP plastic orifices do not adjust as precisely as the older brass/chrome ones IME, but they still work fine.

There's absolutely no difference between these parts for O2 compatibility.

I've never seen a first stage with plastic orifice; they typically have a metal orifice and a hard plastic seat. First stage valves must deal with extreme pressure differentials, while 2nd stages do not.

 

[DA Aquamaster]

I agree with Matt regarding the improved performance of brass orifices in a secnd stage. They are in general a bit sharper than their nylon counterparts and hold up much better over the long term.

I also understand what was said regarding the first state seat in the poseiden. It is a different animal with a metal on metal interface. It works really well - right up until the point it does not, then it gets expensive, so in some respects there is a lot to be said for the inexpensive to replace "soft" seat used in most first stages.

You can argue that a metal seat is "safer" in an O2 environment, but it is just a matter of degree. Given enough O2 and a high enough ignition temp, anything will burn including metals. What matter is that any material use have a high enough ignition temp in an O2 enviroment to make it extremely unlikely that the ignition temp will be reached in normal use. Given the operational realities of seats made from nylon and various other plastics in use on various regs used with 100% O2, it is clear that those seat materials are not problematic in O2 service.

You can go to town all day on therory, but it does not change the facts about what actually works in the real world.

 

[muddiver]

It was the end of the day and I thought the OP had asked about valve seats, it didn't occure to me that someone is actually making Nylon valve orifices. I do agree, why make the pointy part out of a soft material?

My bad.

 

[DA Aquamaster]

I have days like that too...Apparently so do the people who thought nylon orifices were a good idea.

 

[herman]

I have days like that too...Apparently so do the people who thought nylon orifices were a good idea.

*%$&^E$%#!!!! accountants who became engineering managers. Way too many companies are infested with them and more than one great company has been destroyed by them.

 

[HenrikBP]

*%$&^E$%#!!!! accountants who became engineering managers. Way too many companies are infested with them and more than one great company has been destroyed by them.

Don't hold back now ... tell us how you *really* feel

Henrik

 

[Zung]

You haven't seem the legal folks yet!