Hi All,

Please anyone can share your knowledge about three way valve (on/off) with double acting actuator in terms of how it work, do we need one coil or two coil of Solenoid?

Thank you for your help.

Best Regards
Josh

 

I'm not exactly sure what you are trying to do, but let me guess what you want and give some examples:

Application:

- Actuate a pneumatic cylinder that has two ports (one to extend, the other to retract).
- You want to make the cylinder move back and forth with an electrical signal (probably from a PLC or pushbutton, relay, etc ).

If the above is correct you probably need a 4 way valve with a single solenoid. The 4 way valve will have two ports (often A and B) and you swap these on your cylinder to get it to be extended or retracted when the solenoid is OFF.

Some valves offer double solenoids which are useful in a few cases that I know of. Here are where I've used dual solenoids:

- You want to maintain position of the valve when power is shut off. The valve must be of the type that doesn't have a spring return or equivalent in the spool internally (I don't know the term for this valve??). In this case you turn on solenoid A and shut off solenoid B to get it to actuate. To get it to reverse direction you turn on B and shut off A, etc. IF power is taken away the valve spool retains position. This is helpful when you don't want the actuator to take off if a PLC is reset, or the entire machine is shut off at the end of a shift, etc. Much of the equipment we don't do this except for special circumstances.

- Sometimes you want to exhaust both sides of the cylinder (for maintenance, etc). In this case you have a valve with dual solenoids but internally they have the equivalent of a spring return to center when none of the solenoids are energized. (I believe these are called center-off ??). So you maintain power to A and shut off power to B to get it to actuate (and vice versa). The signals must be maintained (not pulsed). If you shut off both solenoids the cylinder will have exhaust to both ports and you can move it by hand (assuming it's a small actuator!). I've used this when I want to actuate something, but then I may have another action that back drives the cylinder and I need to relieve the pressure first. Maybe you load a part into a forming process and the material extrudes upward. I've had a case where I couldn't retract the loading cylinder until the forming operation is complete. I released pressure and it allows the cylinder to be back driven slightly by the forming process. Other reasons are for service (i.e. you can kill air just to that one valve if you wish and technicians can move things without air pressure on them).

I believe a 3 way valve is just one port of pressure or exhaust depending on the state of the solenoid. I suppose you could have dual solenoids similar to above to maintain state of the spool at power down but I've never used one for this type of valve. I've only used 3-ways for spring return air cylinders, but in all honesty most times I've just used all 4 way valves and plug one of the ports. IT is infrequent in my company to use a spring return cylinder and we are not producing many machines so that plan makes sense. YMMV

I'm not a valve expert but I hope that the above was useful and that I got my terms correct. Make sure to check with your vendor before ordering a part in case I got the terminology wrong. I hope that this will make you more educated about different actuators and valves and what questions to ask.

KEJR

 

Josh,

There are many types of three-way valves with double-acting actuators for many different types of applications. Some applications require a lot of torque or pressure to move in one direction, and very little torque or pressure to move in the other direction. Some applications require similar torque or pressure to move in both directions.

A lot depends on the application and on the fluid/medium providing the force (air; hydraulic; electric; etc.).

So, it's very difficult to answer your question without knowing a lot more about the application, the fluid/medium available for the actuator, and the criticality/reliability of the application. Perhaps, the application requires positive torque or pressure in the event of failure.

There's just too many variables involved to be able to answer your question with any confidence that the answer will be in line with your application. Some valve manufacturers may use a single solenoid; others may use two.

This kind of question is best answered by a representative of a valve manufacturer who will usually have some experience with lots of different applications and who can ask the proper questions in order to be able to tell you what the manufacturer(s) his firm represents will best suit your application.

If you can't talk to or email a local valve manufacturer representative you can always consult the on-line catalogs of valve manufacturers--though choosing a proper valve is best done in consultation with a manufacturer's representative who is very knowledgeable or can ask their technical/engineering staff for assistance.

Sorry; you just haven't provided enough information and there are just too many types of valves. If you're having problems with a particular valve, have you tried contacting the manufacturer for assistance?

Most manufacturers have a technical support department or at least someone who can help resolve issues with their equipment--they don't want owners to talk to potential owners and say the equipment isn't or doesn't work well; they're not going to sell much equipment with that kind of negative "advertising."

If you've been sold a valve that's not working properly and you can't get the supplier/vendor to assist, then try another valve manufacturer representative. They are usually very eager to help resolve issues--and sell equipment in the process!

Best of luck.

 

Dear Ken,

Thanks for your advice.

Our application is two pipeline (2 inlet) which will be selected by DCS operator through this 3 Way Valve toward pig receiver, a pneumatic on/off valve.

Best Regards
Josh

 

Dear Sir,

Thank you for your advice.

I have contacted valve manufacturer. As you explained that It can be designed using one solonoid (3-Way) or two Solenoid.

Actually I need know detail instrument air and tubing connection diagram for the valve.

Best Regards
Josh