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I'm working on a project that requires very precise, but low pressure controls. I'm using a pump to charge a chamber to <15kPa, then a manifold of proportional valves to control output pressures from a few channels at around 3kPa with low flow. I've been using the tubing from the pump to the manifold as a reservoir, but I'd like more volume, in the range of 0.2-0.5L. I'd imagine such a reservoir exists for <$50.

A squeeze bottle with some barb fittings is in the ballpark, but I'm curious if there are other ideas. I'm hoping someone can help me find the right terminology here, as all I can find are large tanks when I search 'reservoir' or 'accumulator'.

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    $\begingroup$ "15KPa" is kelvin-pascals. You mean "15 kPa". Capitals matter! A reservoir cartridge may be what you're looking for. $\endgroup$
    – Transistor
    Feb 11 at 7:24
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    $\begingroup$ Make one, a tube of 100mm dia and 15cm long with threaded caps which can be drilled and tapped to match fittings. $\endgroup$
    – Solar Mike
    Feb 11 at 7:27
  • $\begingroup$ Thank you for nitpicking my units :) $\endgroup$
    – HRIGUY
    Feb 12 at 21:02
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I use this kind of thing frequently. The $50 price range is about right for 100mL ish, might be more if you are looking at 0.5L. The max design pressures are generally much higher, but that doesn't matter.

You can buy such things from companies that make pneumatic accessories, and also sometimes companies that make miniature pneumatic cylinders (the "tanks" are sometimes just empty cylinder bodies with an endcap). SMC, Festo, Clippard in the US etc. The terminology varies and internet searches will result in too big sizes. Call up a sales person for a company that deals with miniature pneumatics or industrial automation components. (pneumatics for factory-automation is the most common customer).

It is also fairly trivial to make your own from e.g. from cylindrical tube and custom endcaps that you clamp and seal with o-rings, or from pipe and endcaps and standard fittings. For nicer integration, you can combine with the manifold and have the volume machined into a larger solid block, and simply cap it with a flat plate and a face-seal o-ring. With a split manifold, a number of extra options open up too, you can get a very nice presentation if are trying to sell it. The overall part count will still go down and this can make up for the raw material cost and - the extra machining is quite simple. I have done all these things, it's a matter of what is right for your project.

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High pressure is the critical aspect behind accumulators and storage tanks such as those found for tire inflation.

Your pressure requirements are quite low (15 kPa / 2 psi) which does not pose a danger for air storage. This means that common household items can be used.

You should be able to find a vehicle inner tube to match your volume requirements. If the tube is encased by a tire, safe pressure can be as high as fifteen times your maximum. Without the tire or other enclosure, the maximum safe pressure is likely to be "only" three to four times as high as your maximum.

Other reservoirs can be had in a safe manner. I've constructed air chambers using two liter soft drink bottles which hold thirty times your required pressure (un-modified) and when encased with fiberglass cloth and resin, more than fifty times the pressure.

You've noted that you have used tubing as a chamber, which could be expanded easily to a much larger diameter and length to match your requirements. Even ordinary garden hose is designed to handle pressures of fifteen times your maximum. Hydraulic hoses of various diameters are engineered to support hundreds of times your maximum pressure, but that's bordering on the absurd, based on your requirements.

It is not recommended to use PVC pipe as a pressure vessel, due to the explosion risk but for your low pressure requirements, it is a zero-risk situation.

Your options are nearly endless.

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