Hydraulic pneumatic questions!

[Andron4000]

I am looking at running a high pressure pneumatic system using off the shelf hydraulic cylinders, which as I understand can be used as long as they are down rated by 50%

For off the shelf hydraulic parts, can these be modified, and to what extent, and does this required re-certification?
For example, boring out ports for faster flow rates.

If I were to manufacture my own cylinder, the rules state that all custom components 'must be pressure tested and certified to 120% of working pressure.'
Are there many places that will do this, and what are the typical costs involved?

[Andron4000]

Also the very best of luck to everone up filming at the moment!

[Liftoff]

I don't know what's possible in the UK, but on my island the only hydrostatic testing facilities are scuba or fire extinguisher companies, and they only test cylinders of known origin.
Even if I had to use their service, it's not just a matter of applying pressure up to 120% and that's it - expansion of the component has to be measured etc, ie specific data related to that particular component you designed.
This topic has been picked up before and from what I gathered, as long as the pneumatics don't look dodgy, and you know what you're doing it should be fine. Of course any EO will have the final say, so it's always a good idea to keep them in the loop on what you're building, as they and other experienced members over here may help you with any potential issues.

[Tim The Plumber]

Hi,

I am also trying to make a robot using Hydraulics.

I think I am somewhat behind the curve on the need to know slope though...

I fI buy a hydraulic pump what do I need for the valve/switch thingy? How easy is it to connect one part to another and where do I go for those bits????

And then how do you show that it has been tested to 120% of the opperating pressure?

P.S. And how do you get the cost of it past the wife.....

[terry]

I have a hydraulic pump and directional valve for sale, I'm going to get pics on at the weekend.

[Tim The Plumber]

I have a hydraulic pump and directional valve for sale, I'm going to get pics on at the weekend.

Ah, that sounds like the thing i need...

How much, what capacity, and stuff...

[Andron4000]

Thank you for your posts
I probably caused confusion by calling them cylinders, I am more referring to actuators (rams) than cylinders (fire extinguishers etc.)
I have a feeling the standard 3/8" ports on the off the shelf hydraulic rams are not large enough to allow the flow of a full pressure system. Am I correct?

For our hydraulic set up in Andron4000, we bought an all in one unit from related fluid power. It has a 2 liter tank, 5l/m and runs 24V from a solenoid, so we have a turnigy relay switch to throw it on and off.
The valves are attached to the all in one unit and I think from memory we plan to use another switch to throw them too.

I should probably add that we are yet to get any of this working yet as we are still waiting on our weapon parts to be manufactured!

http://www.relatedfluidpower.com/products/power-units/
https://hobbyking.com/en_us/turnigy-...-switch-1.html

The testing and certification was a concern for us on these, so we went for new, off the shelf parts and read the rules very carefully, and made sure to stay within them ie, no stored pressurisation, invertable, incorporated pressure releif valve, test gauge point

[ThreeFingeredJack]

On topic, how have you solved inverted hydraulic reservoir problems? I've got a vary basic low tech method in mind, just wondering if there's a better (more reliable) option?

[Tim The Plumber]

On topic, how have you solved inverted hydraulic reservoir problems? I've got a vary basic low tech method in mind, just wondering if there's a better (more reliable) option?

I am planning to use the pressure vessel reserve thing that exists in the hydralic world to be the reservoir rather than a tank but I hope that I can use the much cheaper plumbing expansion vessels. I don't know if the hydraulic flid will corrode the rubber air bladder in the expansion veseel....

[Andron4000]

The pump draws from the middle of the reservoir. As long as we arnt on our front we shouldnt draw in too much air.
We did think about expansion vessels, but thought technically a closed system might be considered pressurised...

[maddox10]

Some of the heavies use an accumulator bladder.
Others have used a pneumatic ram, the piston just follows the oil.

Heard about 1 using an 8" inner biketyre.

[Andron4000]

Now that I have my idea all modeled up with the hydralic cylinders in place, I think I'm leaning more towards the idea of a low pressure (16bar) system.

I am worried about the hydraulic components being quite heavy and expensive, as well as the forces from the hydraulic cylinders self destructing with reactant forces.

I'm also concerned about freezing, as the port sizes seem relatively small for a full pressure system, and I don't really want to get into re-certification for modified parts where possible.


I can use a 50bar fire extinguisher co2 tank, or possibly this if it's allowed?

http://www.workshopping.co.uk/produc...LiEaAj_B8P8HAQ


...Through a regulator, (which I am struggling to source. BOC have quoted £280 for one)
into a 16bar low pressure buffer tank.

This should combat freezing and also the reduced force may mean I don't tear myself apart


In regards to the actuator, Norgen cylinders have an operating range up to 16 bar,and an 80 bore cylinder from norgen weighs less than a 60bore hydraulic cylinder.

Festo and SMC cylinders would be much cheaper to me as we use them all the time at work, however their operating pressure is 10bar I think, thought they are tested to 15.
edit: (Just had a check, they are proof tested to 15bar, fittings to 30bar, is this ok to use at 15 bar or do we need to stay at operating pressure?)

I am sure they are capable of taking the forces, where would I get these tested/ certified to stay within the rules?
We do CE mark at work, and use a lot of pneumatics.


With the low pressure system I should be able to use pretty standard pneumatic valves/ fittings/ lines


I get about 740kg running high pressure, and 400kgf with low pressure but much less risk and less self destructive.

[Liftoff]

Regulators go for paintball stuff, there are shimable ones which you can adjust to your required pressure. I doubt you'll be able to find any compact solenoid valves rated 16 bar tho, that said I have successfully used a 10 bar rated 1/8 bsp ported solenoid valve with pressures in the range of 16bar, after sealing the endacaps, because thats from where they leak...don't ask me about certification tho

[maddox10]

Take care.
Normal pneumatic regulators that can regulate 70bar+ to 8 - 16 bar cannot handle liquid CO2.

Paintball regulators have a very low flow, and don't fit on Industrial CO2 bottles.

[Andron4000]

Can the paintball regulators handle liquid co2? Could the low flow rate be combatted with a reasonable sized buffer tank?
if not, does anyone want to sell me some pneumatic stuff?? 🙂