Contorl Valve Help 1

[INSDE08]

Hi All
I need to connect a butterfly valve + elctro pneumatic acutator to the Bialey DCS. But in order ot make it run ON/OFF . How many wires do ineed to run from the valve to the junction Box and to the terminal room.

Is one dekron wire enough?

 

[roydm]

For On/Off you should need just two wires for the solenoid unless you need a feedback switch, 2 more.
For modulating valve you will need 1 pair of shielded wires 28 AWG or greater.
Roy

 

[Loopee]

I'm not sure I'm interpreting your question correctly but it sounds like you have a positioner waiting for a 4-20mA signal and you want to make it work as an On-Off valve?

If that is what you have, then a two wire cable is all you need together with the software set up to ask for 100% open and 0% open. This assumes you dont need limit switch feedback.

 

[Standingback]

The answer is, .... two wires.

However it would be good to know what you meant by "elctro pneumatic acutator" as this could be loosely interpreted as a solenoid (on off in nature), or e/p positioner (modulating in nature)

If it is the former, then you will need a relay output from the DCS with a source of power to match the solenoid rating.

If it is the latter, then you will also require an air supply and the to operate 4-20mA as "on/off" it would reqire the signal to come from a control output from the DCS system. The PID settings in the controller would also have to be set with an infinitely small proportional band and no integral or derivative action.


I trust this helps,
Mlv

http://www.coulton.com

 

[ScottyUK]

Why bother with PID when a simple transfer block controlled by a digital flag gives 0 and 100%? PID just makes for needless complication!



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If we learn from our mistakes I'm getting a great education!

 

[Standingback]

A simple transfer block with a digital flag from a Bialey DCS, will not normally product a mA output . So if your "elctro pneumatic acutator" is actually an electro pneumatic valve positioner. Then you will not have achieved anything.

I accept that if your "elctro pneumatic acutator" has a solenoid fitted with a suitable coil rating, which can be fed directly from the DCS digital output, then I would agree with Scottyuk that a simple transfer block with a digital flag would be more appropriate.

So it still comes down to what is meant by
"elctro pneumatic acutator"

I trust this helps,
Mlv

http://www.coulton.com

 

[ScottyUK]

I don't know the Bailey system but an analogue transfer block with one input at 0% and the other at 100% would drive a 4-20mA output on just about any DCS, probably allowing control of the slew rate when opening and closing. Maybe Bailey is different?

I agree - we are missing some important detail here!


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If we learn from our mistakes I'm getting a great education!

 

[roydm]

Since the original post was May 30th, I would hope it's working by now!
Roy

 

[ScottyUK]

Ha-ha, I hadn't looked that far back in the thread!


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If we learn from our mistakes I'm getting a great education!