Cyclic water pressure testing of rubber hose!

Hi All :)

I am new to the Arduino scene and also learning C.

I have a work related project that if possible/feasible I would like to try and build but before I go off in the wrong direction I would like to get an honest view and guidance from you guys.

I have a rubber hose section 500mm long x 25 mm diameter, that has to be inflated with water to 10bar held for 30 seconds and then the pressure released and the cycle repeated a further 99 times.

I already have a pump (60bar max)

Pressure transducer: This One

12v Solenoid valve: This One

The run sequence would be I think something like this:

Energies solenoid valve (open) ...Start pump (primes the rubber hose) ...after 5 seconds de-energise the solenoid valve ...Pressure builds in the system to 10bar and the pump is stopped ...holds for 30 seconds (pressure decay after pump is stopped due to rubber expansion is not important) ... after 30 seconds energies the solenoid valve (Opens to vent the pressure and then prime the system again) and start the above sequence for a further 99 times.

I know the above is very simplistic view.

Thank you in advance for views and help.

Mac :)

What kind of pump can hold pressure while it is stopped?

why not design the system with a recirculating pump and pressure regulator. Add a solenoid valve to release the pressurized water to the hose, then close that solenoid valve and let the system set for your 30 seconds.

Add a second solenoid valve to release the hose pressure, then close. Start cycle over again.

Your pump doesn't have to stop and start all the time.

Paul

Hi Paul

Thank you for your reply it is greatly appreciated and a perfect reason why I ask questions. :)

I did not think about continually running the pump via another solenoid valve (switching), I had the pump running through a pressure sustaining valve hence build the pressure and stop the pump.

Would the pressure transducer that I am looking at be suitable for the Arduino ?, I shall ponder more on using the pressure regulator method.

Mac

bmac109: Hi Paul

Thank you for your reply it is greatly appreciated and a perfect reason why I ask questions. :)

I did not think about continually running the pump via another solenoid valve (switching), I had the pump running through a pressure sustaining valve hence build the pressure and stop the pump.

Would the pressure transducer that I am looking at be suitable for the Arduino ?, I shall ponder more on using the pressure regulator method.

Mac

This is similar to an irrigation system I have. In the supply/pressure loop are the following, all in series: Water storage tank, outlet at bottom to the pump intake, output of pump to a gate valve to adjust pressure, pressure gauge, and pipe back to the top of the storage tank. I adjust the pressure by closing/opening the gate valve. A gate valve gives finer adjustment of the pressure because it takes 10-12 turns to close the valve.

The output of the pump also has a "T" that goes to the sprinkler system. Your system would have a "T" that would go to the solenoid valve to let the pressurized water go to the hose.

The other end of the hose will have a similar solenoid valve that will let the water pressure out.

So, two solenoids, one valve to regulate the water pressure, and a pressure gauge are needed for your system. And, of course, the pump. Your pressure transducer can go on either end of the hose under test.

Paul

Hi Mac.

That transducer should be fine to connect direct to an Arduino analog input.

The solenoid valve would also be ok, but the Arduino can't drive it directly. You will need a transistor because of the current required. The eBay page says 3.0W which would be 250mA at 12V. However, when the valve is actuated, the current will be significanly higher for a short period. Before you can choose a transistor, you could do with knowing what that current is. You would ideally need a scope to measure it, unless someone has a way to estimate it.

Also you would need a "flyback" diode to protect the circuit from the reverse voltage generated when the solenoid is deactivated.

Paul (we Pauls are two-a-penny around here)

Thank you Paul and Paul :)

"Flyback" diode was something I had not thought of ...Thank you

I think these solenoids can and do peak quite high ... I shall check tomorrow but I seem to remember them running as high as 475mA that was using a bench top power supply! and I guess the longer they run the hotter they get and so on.

Mac

Did you note the pipe thread is 1/4 BSP and not 1/4 NPT? BSP is straight thread and requires a gasket, like an "O" ring. Then NPT (USA) is tapered and is usually self-sealing with teflon tape.

Paul

bmac109: I shall check tomorrow but I seem to remember them running as high as 475mA that was using a bench top power supply!

I doubt you can measure the peak current using the readout on the psu. It will be at its maximum for too short a time (after the solenoid is actuated) for the psu's ammeter to register it. Only a scope will show you that.

a simple pump and an expansion tank would be the heart of the pump side of things. smallest one you can find,

a prv or pressure regulator set to 10 bar.

a solenoid to the hose a second solenoid to dump the pressure, since the total volume is less than one gallon, you do not need much. once filled, the pressure will rise almost instantly.

the solenoids only need to be tiny. the volume of water to pressurize the hose, once filled, will be in the 10's of ml. maybe an ounce.

Hi All

Thank you all very much for your ideas, thoughts and advice it has been greatly appreciated, in light of the fore mentioned I shall take some time to rethink about the way I was going to try/implement this project.

Thank you all very much. :)

Mac