Air Regulator Valves

Discussion in 'The Projects Forum' started by Hurdy, Sep 16, 2006.

  1. Hurdy

    Thread Starter Senior Member

    Feb 27, 2006
    137
    0
    Hi everyone.

    I need some advice for a system I am developing.

    Basically I am looking to control an air pump (as it is for pumping a flammable liquid) that will use an air regulator valve to control the amount of air flow into the pump, thus varying the speed of the pump.

    The fluid I am pumping will have an inline flow meter that will inform a PIC how fast it is being pumped. With the knowledge of how fast the pump is running I will be able to vary the air regulator to speed up or slow down the pump.

    Does anyone know what type of air regulator I will need to allow me to vary to air flow?

    i.e. Do air regulators require a variable voltage to determine how open or closed it should be or do they respond to a series of digital input data bits?

    Thank you for your time,

    Robert Hurd
     
  2. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Why not use a pressure sensor on the air line ?
     
  3. Hurdy

    Thread Starter Senior Member

    Feb 27, 2006
    137
    0
    The reason I am using a flow meter inline with the fluid pumped is because I need the fluid to be pumped at a specific rate.

    Therefore, if say the fluid pipe becomes slightly blocked and the flow decreases, by measuring the fluid rate rather than air pressure it allows the valve to compensate for the blockage to increase pump speed, thus increasing the fluid rate to its required speed.
    If I used a pressure sensor the system will not be able to compensate for such an occurrence.

    It also allows the system to be used on different size pipes etc because it calibrates itself with my method.
     
  4. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Oh well, I thought you were using a fluid line AND an air line.

    Which kind of regulator are you thinking of then ?
    There are both analog types and eg. the PWM controlled types used in EFI systems, so you need to be a bit more specific - like a link to its data or something.
     
  5. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Or better still... Explain exactly what you want to accomplish, it's a little abstract as it is.
     
  6. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    3
    There are many types of air valves or electrical-pneumatic valves available, solenoid actuated ones can only be open or close and these will not be suitable for your application. Linear ones vary wildly on the signals needed. The control signals can be linear voltage (or PWM), current and digital (fieldbus, etc.). Just choose one that suits your needs.
     
  7. Hurdy

    Thread Starter Senior Member

    Feb 27, 2006
    137
    0
    To be honest Soren I don't think I need to explain in more detail what my application is to answer my question. I only say that to save time, I hope that doesn't come across as being rude.

    I am using a system called the CuTouch Industrial Kit from Comfile Technology (USA).

    http://www.comfiletech.com/index.asp?PageAction=VIEWPROD&ProdID=76

    All I all want to know is what type of electronic air regulators there are available on the market to allow me to vary the amount off air flow that I need for my pump.

    I need to know if they are controlled by a variable voltage where say 0v is fully closed and for example 24v is fully open, where 12v would mean half open. Or are they digitally controlled by say a series of digital pulses?

    I’ve never used a regulator before so I just want to get an idea of how they are generally controlled, or what the types available are so I can think about what would be suitable for my control unit.

    Do you understand what i'm asking?

    Thank you for your help Soren, much appreciated.

    Rob
     
  8. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    And that's why you use PWM to control them. Like how it's done in an EFI... They just need to be operated at a (relatively) high frequency.


    How can you tell without knowing the application ?
     
  9. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    3
    Really? Even when the valve is not designed for linear actuation? There you go, I learned something new today.... :D

    Magic power? Crystal ball? Or was it the voice in my head that told me? :p
     
  10. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    What stumps me is that you want to use an air valve for a liquid ?


    They come in all shapes and forms.
    One very important parameter is how fast you need the control to be for any given interval.


    As mentioned, you can have them in just about any methodology, so choose what you think will be best/easiest to control/cheapest/most reliable or whatever is the most important parameter to your app.


    Apart from the airvalve for liquid, yes, but you gotta understand that a valve ain't just a valve, and the application at hand will have a lot to say in which type to choose.

    What is the flow rate ?
    What demands do you have on precision and speed of regulation ?
    If it's indeed a liquid you want to control, why the air valve ?

    I do understand that some people don't wanna reveal what might be a bright idea with commercial potential, but it does make it hard to give useable answers :)
     
  11. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    3
    Ummm... I think it goes like this:

    Air pressure -> Air regulator valve -> Regulated air pressure -> Air powered liquid pump

    Not actually using an air valve for liquid...
     
  12. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Ahh... yes, that might be it, but then I'd wonder if the elasticity might not be a serious problem for any precise system (Now I'll surely get bad dreams of oscillations, but hey, it might just make me forget my fever for a while :))
     
  13. Hurdy

    Thread Starter Senior Member

    Feb 27, 2006
    137
    0
    Hi both, thank you for your responses.
    It's late where I am so I’m going to head to bed now.

    I will just quickly answer your question of why I want to control a fluid with an air valve.
    The fluid is methanol which is flammable and needs to be pumped. So I have an air powered pump rather than an electrical pump so there is no risk of sparking that will cause a fire.
    Then the electrically operated air valve will be used to regulate the pump to its sufficient speed. I don’t want an electrical valve inline with my fluid (methanol) so that there is no risk of sparking and it will be a cheaper option than buying spark protected fluid valves.

    I hope this answers your question on that. I will be back tomorrow to talk about the rest of your questions.

    Thank you,

    Rob
     
  14. Hurdy

    Thread Starter Senior Member

    Feb 27, 2006
    137
    0
    Yes n9352527 has got it.

    Sorry Soran I didn't realise that I hadn't made it clear on how the pump worked. I understand now why you were so curious to know the application. My bad.

    Thank you for your time, you have provided me with some useful information such as my input air pressure that I need to find out.

    Thank you once again both, and I will get back to you soon.

    Rob
     
  15. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
  16. Chris Wright

    Well-Known Member

    Jul 26, 2006
    62
    0
    Perhaps a simpler method might be to use a fixed speed air powered pump that delivers in excess of your requirements and then use a bypass regulator at the point of use to return the excess liquid to the supply tank. I suspect that the regulation of the volume/pressure would be simpler, more accurate and more responsive then trying to control an air powered pump. This is the system used on many cars and aircraft. The regulators are operated by vacuum or air pressure. With out knowing what the point of use requires; i.e. constant volume, constant pressure, any opportunity for feed back, etc. it's hard to suggest a regulator set up.

    I think people are also wondering why an air powered pump when electric fuel pumps are so numerous and specifically designed for flammable liquids? These pumps even operate in the vapors of a fuel tank. And if the required volume/pressure is larger then a car pump will provide, then look to truck and aircraft pumps.
     
  17. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Ahaa, something akin to an air brush... Thanks for clearing that up, i figured a rotor with one side driven by air and the other propelling the fluid :p
     
  18. Chris Wright

    Well-Known Member

    Jul 26, 2006
    62
    0
    HURDY,
    Is this right? Are you trying to use a venturi pump using air to draw a liquid?
     
Loading...