Valves
There are a few basic valve types to select from: line (on/off), needle (flow control), and ball (on/off). I prefer ball valves to control air from each bank since they operate quite smooth at high pressures and their shut-off is virtually absolute.
The other commonly-available high-pressure choice would be coarse needle valves. Needle valves for on/off functionality require a bit of torque to confidently seal off.. I have misgivings over the long-term wear due of this action.
As previously mentioned, sometimes you just have to buy a fitting and worry about the gender later, especially if it's dirt cheap. I bought a dozen of the following valves, that were the complete opposite gender than what I wanted. Although the body is the same as listed, my A few adjustments to the plumbing plans compensated the situation. These particular line valves are best treated as on/off instead of flow-control. When opening them up, sometimes it's like blowing a burst disk when it lets go. To be fair, the model I got had the Whitey brand stamped on the sides of the body, and were not needle valves at all but flat-tipped soft-seat valves. The Whitey, SwageLok, and Nupro brands all belong to one company.
One word of caution about teflon and nylon stem-packings when you re-assemble valves that employ it: Do NOT over tighten the bonnet nuts unless the torque is specified. Even using a wrench with just two finger-tips on it can over-tighten the packing and cause it to squish from beneath the bonnet nut along the stem. My strategy was to get the bonnet nuts finger-tight and then give them about a 1/4-1/2-turn with a wrench. Once you put maximum pressure on the valve, you can tell if it needs tightening further from the hiss of gas leaking up the stem past the packing. I tighten the bonnet-nut only enough to stop the hiss. Turn the valve on and off several times to make sure it is not leaking any more, as it will sometimes start leaking again when it the stem moves until the bonnet is tightened enough. A few line (on/off) valves will may hiss when the are opened all the way up. Sometimes just a half or full turn clockwise will seal it. Other valves may leak until you tighten the knob all the way open. Generally the bonnet nut can be tightened down to prevent this, but there is a point-of-no-return where further tightening will deform the packing and reduce its sealing capability.
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SS Integral Bonnet Needle Valve, 0.21 Cv, 1/4 in. MNPT x 1/4 in. FNPT, PCTFE Stem MSRP is $71 each. I won 16 of these for $24, most likely because the sizes were advertised as 1/2" instead of 1/4". The seller must have measured the male OD with a ruler. It pays to obtain the model and look at the specs! You'll notice in the picture below a few of these valves screwed into the brass manifolds with the QD's screwed into them. I basically used these for on/off functionality
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I
purchased several high-pressure ball valves, although a couple
had a 3/8" tube fitting (there's one in the picture to the left) instead of the usual 1/4".
The ball valve bodies were identical with just a different-sized fitting screwed into the valve's body. I later
found and bought some
3/8->1/4 tube reducer couplings
(along with a batch of other odd fittings that were being sold as a single eBay
lot) that offered a solution. You will notice one of these 3/8 ball
valves separating my oxygen and mix manifolds.
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SS 3-Piece High-Pressure Ball Valve, PEEK Seats, 3/8 in. Swagelok Tube
Fitting MSRP: $175 eBay: two SS-83PS6 for $56.. This valve comes lubricated from the factory with graph-oil, which is a mess to clean and not something you want to expose oxygen to. When I took the first one apart for ultrasonic cleaning, I discovered that it has 48 pieces. |
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SS 3-Piece High-Pressure Ball Valve, PEEK Seats, 1/4 in. Swagelok Tube
Fitting MSRP: $175 eBay: four SS-83PS4 for $108 |
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Whitey SS 1-Piece 40 Series Ball Valve, 0.9 Cv, 1/4 in. FNPT MSRP $67 eBay: one SS-43F4 for $10. I was planning to use this valve on the oxygen bank, which I never planned to operate over the service pressure of this valve (3000 PSI) at first. |
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SS Severe-Service High-Pressure Union-Bonnet Needle Valve, 0.35 Cv, 1/4 in.
FNPT, Regulating Stem MSRP: $203 eBay: one SS-3HNRF4 for $17. |
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SS Integral Bonnet Needle Valve, 0.21 Cv, 1/4 in. FNPT, Vee Stem MSRP: $74 eBay: one SS-20VF4 for $10. I used this valve as an on/off valve for the line from the filter banks to the air-banks |
For the oxygen and mix lines, I wanted needle valves so I could slowly ease
pressures up to the right PSI range for partial pressure remixing. It was helpful
in that the ones I bought had MNPT on each end and allowed me to screw them right
into the manifolds or tees where needed.
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5,000 PSI, 1/4"
NPT, stainless steel needle valve 5,000 psi @ 70°F Temperature Range: -65°F to +400°F Orifice: .079" Diameter
MSRP (est. $50-$90). eBay:10 SS14M14MS for $170, which was an accidental, gross over-bid, but still worth the money.
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I used 6,000 PSI Parker-brand check-valves to isolate the lowest-three air banks from each other. This is useful for cascade-filling all three air banks at once without equalizing them to start Think of this as a reverse cascade design.
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Parker
4M-C4L-10-EPR-SS check valve
MSRP: ? eBay: two for $20. I've seen them for $4-8 each |
I also picked up some fine-mesh line filters. Of most concern is the air coming out from the filter stacks. There's only one pad in the last filter separating activated carbon (in most cases) media from your air banks, and a fine filter like the following should keep it from ever making it much past the filter banks. There is some concern as to how much of a pressure differential these filters could withstand should the line sudden pressurize or depressurize for any reason.
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Nupro Stainless Steel Tee-Type Particulate Filter, 1/4 in. Swagelok Tube
Fitting, 60 Micron Pore Size
MSRP: $74. eBay: 4 for $60.50 |
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Stainless Steel All-Welded In-Line Filter, 1/4 in. Swagelok Tube Fitting, 2
Micron Pore Size MSRP $70 eBay: three for $46.50 |
I originally wanted some fine-control brass needle valves for decanting directly from supply bottles, and I finally located some small-cf ones after watching eBay for needle valves over several months
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Ideal 52-2-14 angled
precision metering valve 0.08cf ,1/8" FNPT, 3000 PSI MSRP ? eBay: two for $30 |
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1 - Introduction 2 - Bank Bottles 3 - Fittings 4 - Tubing 6 - Manifolds, whips, gauges,O2-cleaning 7 - Results & Pictures