Design of air pressure regulation within a container 3

[JohnMechEng]

Hello everyone,

I am new to this website and came across it from a Google search, hope you're all doing well
I am looking for some advice/help with a project that I had in mind.

Here is the basic idea:

[ul]
[li]I am looking to have air flow/gently pumped into a closed container and be able to increase/decrease (regulate) the air pressure within the container. I would also like for an air pressure sensor to display the pressure within the container.[/li]
[li]What kinds of parts would I need?[/li]
[li]Is this project even possible?[/li]
[/ul]
I am looking to make it on a mini scale, so no bigger than the size of a hand/fist.

Thank you for your time, consideration and help!

 

[zeusfaber]

Is it possible? Of course - it's done all the time at all sorts of scales, from a half litre sampling cylinder all the way up to the fuselage of an airliner. The trick is doing it without having to pick fragments of the container out the back of your eyesockets afterwards.

In general, you will need:

A container that is strong enough to contain something like three times the highest pressure you want to attain. At the size you are talking about, provided your intended pressure is low enough, you may be able to do that based on engineering judgement. At higher pressures or volumes, you are highly likely to find that the decisions about container strength are very heavily constrained by law (for really good reasons).

A relief valve on the container outlet to govern the pressure attained within. You might want to make this adjustable. The valve will need to be capable of venting the maximum flow that can be generated by your air source.

A safety device that will safely vent the container to close to atmospheric pressure should something go wrong with the standard arrangements (for instance, the relief valve getting blocked, or your air source going into overdrive). This often takes the form of a bursting disk chosen to rupture somewhere over your highest planned working pressure and well under the burst pressure of the container. Once ruptured, the disk needs to leave a hole big enough to vent the maximum credible flow from the air source without maintaining unacceptable pressure.

Pressure indication? For very low pressures, a water manometer is cheap to make. For higher pressures, standard diaphragm or bourdon pressure gauges come in all sorts of pressure ranges. Alternatively, several suppliers (mine come from Parker) do pressure sensors that convert pressure to a linear 0-10V or 4-20 mA signal over a selection of convenient pressure ranges.

Think for a minute about whether you also want to include a controlled way of completely depressurising your container when you've finished whatever it is you're doing so you open it up.

A.

 

[LittleInch]

Zuesfaber has it right.

First you need to figure out your internal pressure and flow and that leads to all the required safety features mentioned above being applicable or not.

The material you make it from also has a lot of impact on the design. Some materials (PVC for example) can shatter into a thousand pieces if they fail ( this nearly did me serious injury some years ago) and can fail due to fatigue compared to more ductile materials.

Without more specific details it is difficult to comment further than the excellent post above.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way