O-two regulator seat material

[rolanddiver]

Good Morning/Afternoon,

We have 3 O-two adjustable medical oxygen regulators that we use on our Nitrox blending sticks for flow control. 2 out of the 3 no longer work as the seat material has worn out and it leaks. I wanted to purchase the parts from the mfg, but they wouldn't sell direct and there are no service centers in Europe. I figured that I can machine a piece of plastic and just replace it but no luck. So far I tried polyamide (way too hard) PTFE (aka Teflon) and polyethylene but it still leaks slowly but surely. Do any of you know what would be the best plastic to use for such seat inside a pressure regulator? The original plastic in the seat was so soft, that I could easily scrape it out with a dental pick. Below is the picture of the part(s) in question. Your help is greatly appreciated.

Very Respectfully

Roland

 

[rjack321]

PTFE is the most oxygen compatible material, unfortunately it is too soft and will "flow"

Most seats are actually made of nylon even though it not really that oxygen compatible. When they oxidize they get soft and crumbly. If you do replace it with nylon, be sure to wash it after cutting and handling it and before use. Then perhaps the first few times move the cylinder and regulator outside. You still may burn down the shop or worse.

The safest option is to buy a new regulator O2 clean and compatible from the factory

 

[GJC]

In my experience working in the medical field, medical oxygen regulators are never serviced or rebuilt, they are just replaced. They are not that expensive and have a long life even when in constant use. You probably have gotten your moneys worth out of those regulators and should just replace them.

Replacing the seat without knowing what material it should be replaced with is probably not the best idea. At best, it's just going to start leaking again after a short period of time. At worst, it can explode.

 

[rolanddiver]

Thanks for your replies. Much appreciated.

Roland

 

[iain/hsm]

Your problem stems from the poor choice of regulator you are using in the first place.
Medical oxygen regulators are notoriously poor in performance when you consider the light duty application they are used in.
Maximum flow of around 30 lpm against a lung function inhalation effort and work of breathing demand from a half dead asthmatic 90 year old being is about the hardest work of breathing they are expected ever to operate under.

A product purchased at the lowest tender bid manufactured out back in some sweat shop in China with a fancy yankee Medic badge stuck on it. Any wonder it’s not working while the good folks who imported it can’t get you spares.

Now consider that against your application jamming gas down the thing at around full bore flow for hours on end entraining oxygen into your home brewed concoction of a mixing stick.
Now if you place a $60 high pressure 2Mu filter prior to that soft seat that would have helped.

Frankly blasting the polymer seat away at the contact line doesn’t do regulators that much good. But if you look carefully at your two photos the contact area is huge, for a small medical oxygen regulator.
Make you wonder if it wasn't designed by a Aqualung scuba shop sports and fashion house.

Also that huge clump of soft (flammable) polymer plastic just waiting to be the fuel for the fire and kindling effect makes you wonder if these medical folk even know what an oxygen regulator should look like internally. It beggars belief that they even know what’s inside as they just discard them and buy new.

However if you wish to re make the seat you could try a 3M PCFTE material originally called Kel-F now known as Neoflon M400H I guess due to someone who bought the company being a big Matrix fan.
The other oxygen compatible seat material to consider is a polyurethane polymer known as PU109
Hope it helps, some may disagree. Iain

 

[rolanddiver]

Thanks for your detailed reply. Much appreciated. Two days ago I actually managed to make both work by using Polyurethane.

Very Respectfully

Roland