Creating a Pressure Cycler

[RontotheB]

Hello all,

This is my first post! Anyway, getting to the point, I'm trying to put together a pressure cycler that will be used to test a valve. The pressure will cycle from 2000 to 3750 psi, for a total of 20,000 to 40,000 cycles. Although my expertise on pressure cycling is limited (especially in the area of automation), I have recognized several issues that I hoped someone be of service in, in terms of ideas for a setup.

I have a pressure supply of 3500 psi (a Nitrogen/Helium gas mixture), which falls below my test requirement of 3750 psi (see above), so the first thing I might need is something that could boost the supply pressure. I'm not sure what exactly could do this (perhaps a pump of some sort?), but any information would be very helpful.

Once the supply pressure has been boosted, would a 3-way solenoid valve be a means to perform the cycling? I'm guessing one outlet would be exposed to ambient air, with the other outlet connecting to our valve, and the inlet connected to the pressure supply.

Again, going out on a limb here, I'm guessing I'd need a way to control the pressure automatically such that the pressure cycles from 2000 psi to 3750 psi seamlessly (ideally less than 10 seconds per cycle). I'm not sure what kind of electronic controllers/transducers I'd need, but any ideas on what kind of setup or parts I'd need would be very welcome.

Thank you!

 

[BigInch]

I think you might get the valve pretty hot doing that in 10 seconds for 40,000 cycles. Hopefully you won't be using air-testing to failure. 3750 psi gas pressure doesn't make a very controllable failure.

I would also consider venting the 3750 back to a 2000 psi (or slightly less) empty bottle and recompressing that back to the HP requirement to avoid simply wasting that energy and the helium away to atmosphere.

Valve selection shouldn't be that much of a problem. Any of several automatic valves, 1, 3-way valve would seem to be an acceptable arrangement. Don't forget a pressure relief valve.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[unclesyd]

There are a couple of ways to approach your problem. Probably the lest expensive would be to use diving compressors and valves. The compressor are straight forward with the exception that you should mention that your are adding He to N. On some types of compressors this will have a considerable effect on the discharge pressure. Right off hand they are two types of valves, toggle, Fill and Bleed, that might do the job.

http://www.northshorecompressor.com/newcomp.html#CS9

http://www.scuba.com/shop/product.asp_category_155

http://www.rixindustries.com/products_bair.html

Another approach would be to use gas boosters from people like Sprague. They could also build you a completed test stand.

http://www.spragueproducts.com/Products/spokes/gasBoosters.htm

For He recovery as mentioned above you can use a gas bag and booster if you don't want to maintain a higher gas recovery pressure use a bag from Quantum. Both Quantum and Rix (above) have gas booster compressors.

http://www.quantum-technology.com/HTML/q090cat.htm

 

[SteveWag]

A high pressure gas cylinder, not a tank, but a cylinder with a piston, filled with your 3500 PSI tank pressure when at mid-stroke, with the piston moved back and forth using a motor, crankshaft and connecting rod for motion should provide a Hi-Lo pressure once per stroke. Your only moving 6 RPM, for a 10 second test, and no lost test gas just make up the leakage loss. You can test 1 per week.

Steve Wagner

 

[unclesyd]

I like and think the idea proposed by SteveWag is viable and quite doable. Either take his approach with crank and piston, reciprocating compressor or modify a gas booster or gas intensifier to do the pressure cycling. The approach you will depend on the volume of gas need to effect the pressure swing.

Can you comeback with more information and to the volume of gas required?

Is this a one off test?

 

[RontotheB]

Thanks everyone for your input. As far as creating that piston setup, I don't really have the tools to build that (or build it well) in house. Safety is also a concern, especially if I modify a high pressure cylinder. I wouldn't want to weaken it structurally in my modifications. Unclesyd, The gas booster sounds like a great idea, and I'll probably make use of that.

BigInch, I'll keep that heating in mind, and I probably won't adhere to that strict cycling time.

As an update, I've also determined that I will use strictly Nitrogen and no Helium.

Here are my thoughts so far:

I've looked into making a T-shaped apparatus. On one end will be our test fixture, on the other end will be a supply valve connected to the supply pressure of 3750 psi, and on the last end will be a bleed valve connected to a reservoir at a pressure of less than 2000 psi. The idea is to build circuits using pressure switches such that below 3750 psi the supply valve is open, pressurizing the test unit to 3750. When the pressure hits or exceeds 3750 in the test unit, the supply valve closes and the bleed valve opens until the pressure is reduced to 2000 psi. Then the bleed valve closes, the supply valve opens, the pressure increases, and the cycle repeats. Timing between valve closures and openings might take some thought.

Does this sound viable? This way I'd have to manufacture few to no parts; it would just be a matter of purchasing them and putting them together. Any thoughts?