Valves and DAQ selection

[kllim]

I am a newbie in Labview and planning to build a hydrogen charge/discharge system (process flow diagram is attached) but I have no idea where to start with.

I need to actuate the valve from the hydrogen feed to a desired pressure, hold for a few minutes, then release through another valve.

For this purpose, I plan to acquire NI USB-6343, but I have no idea which type of the valves can work with it. It is much appreciated that anyone (or anyone that has experience with this design) can provide me suggestions about the possible valves that go well with this model.

Thank you.

[Richard2950]

Take a look at http://www.omega.com/ and look at their pressure section. They have a variety of electronically-controlled valves. Solenoid valves are cheap and simple, and can be controlled by a digital output line and a solid state relay. They are open/close devices and might be too sudden for your used. There are proportional valves that can be adjusted continuously from opened to closed by means of an analog voltage. Those can be used to open and close slowly to avoid any pressure surges. Be sure to get a valve that is rated for use with hydrogen!

Richard

[kllim]

Thanks Richard.

As a safety measure, I think I will control the valves pneumatically. So the solenoid valves that I am looking at will be controlling the compressed air that operate the pneumatic valves.

The solenoid valves that I have now are from Nass Magnet (attached) and I am still considering if I need to replace them so that they are compatible to the DAQ. I am not familiar with the label on electronics, does 24 V - 4.8 W on the label indicate that the valve is controlled with 24 V? Does that mean if the DAQ NI USB-6343 with 10 V output can only open the valve partially? How can I tell the valve is operated as open/close device or proportional?

[Richard2950]

Your 10 V AO output on the USB-6343 board will not work for the solenoid. These valves will not move unless the voltage (actually the current) is high enough. Your AO voltage is too low, and it cannot supply  enough current (4.8 W/24V = 0.2Amps).

Most simple solenoid valves are open/close, and this one looks to be that way. You need to supply 24 VDC or 48 VAC to operate it. You can control a relay with a digital output and use the relay to switch the 24 VDC or 48 VAC to the solenoid. You have to find a relay that will operate off of the low voltage/current that your digital output can produce, or use a transistor or other buffer to drive the relay. That topic has been discussed elsewhere on the forums.

Pneumatic control is standard for many industrial valves, and many proportional valves use a range of 3-15 psi for control from open to closed (or vice-versa), although other ranges are also used. There are standard devices that take an electrical control signal (0-5V, 0-10 V, 4-20 mA) and produce the 3-15 psi. Be sure to find one with voltage control, because your USB-6343 can't produce a 4-20 mA signal. The IP411-X15 from Omega will work on 0-10V and produce 3-15 psi for $160.

Richard

[Richard2950]

Some further advice for the future is to select the valves first and then pick a DAQ device to drive them. You can often simplify the system and gain in cost and reliability by eliminating conversions from one type of control to another. For example, you can use cDAQ modules that  produce 4-20 mA directly or have relay outputs.

Richard

[kllim]

Thank you Richard once again.

It seems like my problem is growing like a snowball

Anyway, the pneumetic valves that I am planning to use is Swagelok bellow valves, which operate within 30 - 110 psig:

http://www.swagelok.com/downloads/WebCatalogs/EN/MS-01-76.pdf

It will be good if there you know there is any suitable Omega solenoid valve that's compatible with the bellow?

Alternately, I will look for a suitable DAQ that work with the Nass Magnet valves.

[Richard2950]

The SwageLok valve that you are planning to use is an open/closed valve, not a prooportional valve. The range of pressures given (30-110 psi) is the maximum allowable actuation pressure for the range of working pressures, NOT a proportional control range. Look at the graph on page 2 of the link you sent. For working pressures (i.e. the hydrogen pressure) below 500 psi the actuation pressure is 30 psi. As the working pressure goes up the actuation pressure also rises as the working gas resists the closing of the valve. The actuation pressure should not be more than 30 psi over what is shown in the graph. Almost any solenoid valve will be able to supply a 30 psi control pressure, and most will supply the 5 bar (or 5x15=75 psi) maximum required. Look at the detailed specs to be sure. Attached is the Nass Magnet catalog for your solenoid. Look at page 9 for part number 0550 00.1-00/4982. This is a modular system and that part number only applies to the solenoid coil, not the valve itself. You can mix and match valves and solenoids within their "system 8" series. All of the valves seem to be able to handle at least 7 bar, so your Nass Magnet valve should work  just fine as long as you have a way to actuate it.

Any more questions and we should take this offline (and I should collect consulting fees, or at least Kudos).

Richard