I'm about to purchase several solenoid valves (will be used as an ON/OFF valve/ball vavle). My questions are:
1. can someone inform me more on the solenoid valve. i.e. why we use it, when to use it and when should we not use it
2. The flow I sent the vendor is in slpm, and the fluid is gas (don't ask me why the designer of this unit loves to use slpm instead of mass rate). the vendor came back with Cv value and when I looked at their website, the Cv value is based on water. Can someone tell me how to interprete a given value (Cv), to check whether the quoted valve will be the right size to use?

Can I still use a valve program, plug in all the conditions, enter the Cv and let the program calculate the max flow? Then, compare the calculated flow to the operating flowrate to make sure is not undersize?
Does it matter that I use a Cv of fluid (water) to check wheter the valve is good for a vapor type of flow?

1) Why do we use solenoid valves...Because they are a cost effective and reliable way of turning electrical energy into linear force.

We use them when we want to move something. Valves, switches, latches, many mechanisms can be moved with solenoids.

Their use is limited by the application and cost. In automotive applications, over a certain power, solenoids tend to become quite large and the cost becomes prohibitive.

Some explosive applications mean the solenoids are not viable for obvious reasons. However, there are many hazardous applications that do have solenoids and solenoid valves.

There are solenoid valves on the atlantic seabed and the the are solenoid valves on space craft. Solenoid valves are ubiquitous.

Solenoid used with valves can be digital. i,e on or off...or proportional meaning for they move a precise amount for a given electrical current input.

But that's a lesson for another day...

2)Answering that question is tricky.

The Cv value is for water flow with a delta P of 1 PSI. A valve will handle much much more gas with a delta P of 1 PSI.

It might be better if you tell us the the type of gas that you are using, as well as the flow and pressure rate required and any other important details.

There are direct action solenoid valves and pilot operated solenoid valves.

Direct action will close against the rated inlet pressure without any minimum DP across the valve.

Pilot operated solenoid valves depend upon a minimum pressure differential across the valve to assist in the action of the solenoid.   Without the minimum DP, the valve is unlikely to actuate, even when energized.   

Make sure you get the right style.

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