Classtime 

I think I have the used tank thing figured out enough to be comfortable with taking the tank to my LWS and get it tested for $25-30. While I continue searching for a good price on an oxygen concentrator, I'm looking at a second hand Meco single stage Oxygen regulator with stainless steel diaphragm and would like to know if it is relatively straightforward to test it on m own. I'll be using propane if that makes a difference.
Thanks,
Jeff

Nessism

One issue with used tanks is the gas companies won't fill them unless they are within some certain inspection shelf life, and testing the tanks and getting them recertified costs $.

bulgie 

While I'm not an expert on testing regulators, I'll tell you what I do.

• Wear eye and ear protection. Blast a tiny blast of O2 out of the tank to clear any dust or spider nests out of the tank orifice. Some suppliers have taken to shrink-wrapping the valve for this reason, so hopefully the tank side is clean.
• Eye-ball the orifice on the reg to confirm it's clean. I've never had to clean the reg orifice, but if you do, don't use solvent or anything flammable. Even some fuzz off a Q-tip could be hazardous, or the propellant in one of those canned-air blasters, or the compressor oil that comes out of your shop blow-gun. Treat the high-pressure side of pure O2 with massive respect.
• Mount the reg on the valve, "pretty tight" but no need to hurt yourself (sorry I don't know the foot-pounds). Do not use grease/oil or thread tape., just clean dry threads
• Back out the regulator adjustment, the one that sets the low pressure. You want zero pressure on the low side when you open the tank valve.
• Stand aside while opening the tank valve, in case the reg blows. If there's oil in the high-pressure side of the reg, it doesn't just burn, it detonates. Crack the valve then open it slowly.
• When the high-pressure valve reaches its max, open the valve another turn or two, no need to be slow about it anymore and the exact amount isn't critical. Some say to open it all the way, but I have never found that to be necessary, and it will slow you down if you ever need to close it in a hurry.
• Adjust the low pressure side to a medium setting, normal for your usage, i.e. 5 to 10 psi for welding or higher for cutting.
• Open the O2 valve on the torch so you're letting gas escape at a rate similar to your normal usage. Since we're just doing this for a half a minute you don't need to light a flame, unless you're in a small enclosed space where the increased O2 would be an explosion hazard. Don't point the torch at anything flammable; with pure O2 even at low pressure some things will spontaneously combust.
• Watch the low-pressure gauge to see if it creeps up. If it stays steady, this test has passed. It's OK for it to drop a little right when you open the torch valve, but then it should hold steady neither climbing nor dropping.
• Close the torch valve, and watch the low-pressure valve to make sure it doesn't creep up. It's OK for it to go up a little when you shut off the torch but then it should hold steady. I'd give it a minute or two, longer if you're not in a hurry. Low side creeping up is a common sign of a faulty reg .
• Close the bottle valve. See if the pressure drops. If it does then you have a leak. It might not be in the regulator, could be hose/torch etc. but you need to find it. Soapy water is the classic method, see where it's blowing bubbles. Again give this test as long as you like but a few minutes at least.

There may be more testing an expert would do, but that's all I do.

If the regulator needs rebuilding and it's a name brand with repair parts available, the job is easy. There are youtubes showing it in detail. Two-stage regs are more complex, but you mentioned a single-stage and those are pretty simple inside.

If the reg needs rebuilding but there aren't any spare parts available, slap yourself for getting a throw-away reg, and make sure the next one you get is rebuildable, preferably American made. I'd rather have an '80s vintage Harris, Victor or Smith over a brand-new Chinese POS any day. The good old ones are infinitely rebuildable, so they're fairly safe to buy on ebay or CL. I just got a set of old massive bomb-proof two-stage Harris (oxy & acetylene) on ebay for $80 (shipped, incl.tax) and they work perfectly. Regs like that would be $200-300 new EACH, only the new ones aren't as cool-looking... Two-stage is seldom needed but it is nice to have, especially if you use the torch all day — outlet pressure will not change as the bottle pressure goes down. Just a luxury for me now that I'm not a full-timer anymore. Lots of pros go their whole career with single-stage regs though, so don't worry about it. Just buy quality.

One more tip, don't settle for the low-pressure gauge that goes to 200 psi. For brazing, your pressure range will not even make it to the very first tick off the the peg, very difficult to make fine adjustments. Look for one with low side gauge that maxes out at 60; then your normal usage pressures will be more visible. That's an option you can spec when buying a new reg from the better brands, but if you're stuck with one with the 200 psi gauges, on most regs they're extremely easy to replace. A new 0-60 psi gauge can be had for under $10. Most take a 1/4" NPT (pipe taper) thread. You need special non-flammable thread tape for use with O2, don't use regular plumber's teflon tape. Let me know if you can't find it, I just bought some, so I can find you the link, it was cheap. (My ebay O2 reg had the 200 psi gauge, so I've just been through this.) Without the tape it can be difficult or impossible to get the gauge to face forward when it's tight.

{EDIT} I just looked at my main O2 reg and its low-side gauge goes zero to 30, not 60 as I wrote above. 0-60 is better than 0-200, but keep an eye out for a 30 psi gauge, even better IMHO.

Mark B in Seattle

Andrew R Stewart 

Years ago this was a lot easier for the hobby/home person but insurance and safety guidelines have tightened up a lot. The welding supplier I use won't even test other's tanks any longer. When I moved back to Rochester I found it easier to just let them dispose of (properly and safely) my old tanks and lease me new ones that they are happy to handle. Andy

bulgie 

In Seattle we have a place called Fire King that tests cylinders for a very reasonable fee, ISTR about $25 or $30. As the name implies they specialize in fire extinguishers but test all cylinders including scuba, welding, you name it. They're a great place to buy new or reconditioned cylinders too, way cheaper than the welding store. Hopefully there's a place like that near you. Leasing cylinders makes less sense if you use the gas very slowly, as hobbyists tend to do.

Mark B in Seattle

Classtime 

Following up with additional questions: I think I got a good deal on the tank and regulator. The tank is getting re-certified. My question is regarding sealant tape for the regulator fittings. I read that most thread sealing tape is oil based and a no-no. But when I removed the barbed hose fitting to replace it with threaded, I see that white thread tape was used and I also see some white tape on the threads of the gauges.
1. Should I leave well enough alone wrt to the gauges?
2. Should I try the new hose fitting without tape and if it doesn't leak I'm good?
3. If I need sealant tape, what is the recommended tape to use? (I want to have everything on hand when I turn on the gas.)




Thanks. I'm getting close.
Jeff

Doug Fattic 

This won't be a complete answer but it can get you started in the right direction until someone else can be more specific. There is yellow teflon like tape that is used for welding regulators and hoses. I've understood that standard white tape is a no-no too.

unterhausen

There apparently is oil-free pfte tape. If you search for "sealant tape oxygen" on mcmaster carr, it lists a number of tapes, but the information they give about it is not fully satisfying

bulgie 

Here's the stuff I use, specifically called out as being for oxygen.

It doesn't matter for fuel regs, and even for O2 it probably doesn't matter so much on the low-pressure gauge or the outlet thread. Don't quote me (or trust me) on that though. I've heard it can fail pretty dramatically (like explosively) if used on the high pressure side of O2, but I haven't experienced any such booms myself. It just seems to be in the 'oft-repeated lore' department.

Mark B in Seattle

Classtime 

Cool. Thanks Mark. Green is Good.
The welding forums searches result mixed messages and none of the L.A. area welding supply carries anything but white.
It will be here tomorrow.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1