11 replies to this topic

[mm217]

Dear all;

 

I would appreciate if any one could help me understood this matter.

 

1. I believe that failure open or failure close of the control valve is something related to position of the valve in case of failure of the instrument air to the valve. It means when the instrument air cut off , the control valve could possibly close or open consequently. We can have the control valve which it is normally close but it is failure open or vice versa.

But when we have the control valve with solenoid valve. Imagine the case that we want that control valve closes or opens in case of especial signal. Then we order the valve to open or close via solenoid  in that case if the solenoid close the valve are we have to say that valve is fail close one?! or it is not related to function of the solenoid valve....

I wish i could convey the meaning better....

 

2. Do the all on/off valves have solenoid for their action?

 

I'm waiting for your kind guidance.

 

mm217

[pavanayi]

mm217,

Your questions is a bit confusing, but let me try and address your query (based on a typical installation of solenoid on the instrument air to a control valve).

 

When you have a standard control valve, you have the instrument air going into it. The control valve maybe fail open (which means it should open when instrument air fails) or vice versa.

 

When you have a solenoid attached to a control valve, the instrument air goes to the control valve through the solenoid. The control valve itself was as previous (fail close or fail open), but with a new equipment that delivers the instrument air. What the solenoid does, when actuated, is to shut off the instrument air to the control valve. Either it shuts the air, or diverts to atmosphere etc based on the valve type.

So, essentially the solenoild prevents the air from going into the control valve, when the control valve will go to its fail position. (open or close).

 

In short, fail open or fail close is associated with the control valve.

Solenoid valve on the instrument line is an on/off valve that either provides or cuts off instrument air to that particular control valve. When actuated, it forces the control valve to go to its failure position.

 

 

•  

[Zunair]

Dear mm217,

 

As explained very nicely by pavanayi typical solinoid valves are attached to the instrument air that goes to the control valves.A solenoid valve is an electromechanically operated valve. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports.

Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.

The Solenoid Valve diverts the flow of instrument air towards the control valve resulting in failure of air to the control valve corrosponding to which the control valve will behave as per design Fail-open or Fail-Close. 

 

Thanks and regards

Edited by Zunair, 29 April 2013 - 10:02 AM.

[mm217]

mm217,

Your questions is a bit confusing, but let me try and address your query (based on a typical installation of solenoid on the instrument air to a control valve).

 

When you have a standard control valve, you have the instrument air going into it. The control valve maybe fail open (which means it should open when instrument air fails) or vice versa.

 

When you have a solenoid attached to a control valve, the instrument air goes to the control valve through the solenoid. The control valve itself was as previous (fail close or fail open), but with a new equipment that delivers the instrument air. What the solenoid does, when actuated, is to shut off the instrument air to the control valve. Either it shuts the air, or diverts to atmosphere etc based on the valve type.

So, essentially the solenoild prevents the air from going into the control valve, when the control valve will go to its fail position. (open or close).

 

In short, fail open or fail close is associated with the control valve.

Solenoid valve on the instrument line is an on/off valve that either provides or cuts off instrument air to that particular control valve. When actuated, it forces the control valve to go to its failure position.

 

 

•  

 

Dear Pavanayi;

 

I think your explanation is pretty good!

I thank you a lot. Indeed I was skeptic about the location of the solenoid on control valve and you assure me that it would be installed on the main instrument air line of control valve. So it would affect the FO/FC type consequently.

 

Regards;

mm217

[mm217]

Dear mm217,

 

As explained very nicely by pavanayi typical solinoid valves are attached to the instrument air that goes to the control valves.A solenoid valve is an electromechanically operated valve. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports.

Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.

The Solenoid Valve diverts the flow of instrument air towards the control valve resulting in failure of air to the control valve corrosponding to which the control valve will behave as per design Fail-open or Fail-Close. 

 

Thanks and regards

Dear Zunair;

 

Thanks for your kind accomplishment.

It was helpful.

 

Regards;

mm217

[mm217]

Dear all;

 

I appreciate if you give your opinion about attached drawing.

This is part of a project design.

Regarding above posts, it seems that XV-50HR001 should be fail close since the solenoid will close the valve in case of HH level the tank.

Now, consider the situation that we want that XV to be fail open (I mean maintain as open state in case of instrument air failure. That is when we need storage in downstream tank even overflow might be possibly occurred ) then we might consider another valve upstream that XV to close in case of HH level. Is it rational to consider consecutive valves with two different failure mode?

 

Regards;

Attached Files

•  XV sample.png   33.75KB   35 downloads

Edited by mm217, 30 April 2013 - 05:00 AM.

[fallah]

 then we might consider another valve upstream that XV to close in case of HH level. Is it rational to consider consecutive valves with two different failure mode?

 

mm217,

 

Then existing XV to close in case of which process upset?

[mm217]

 then we might consider another valve upstream that XV to close in case of HH level. Is it rational to consider consecutive valves with two different failure mode?

 

mm217,

 

Then existing XV to close in case of which process upset?

Fallah;

 

Existing XV will close in case of HH level of Holding Tank (I-012).

[fallah]

Fallah;

 

Existing XV will close in case of HH level of Holding Tank (I-012).

 

mm217,

 

As per my understanding both of two consecutive XVs, with different failure mode, will be closed in case of HH level in holding tank. Am i right?

[mm217]

Fallah;

 

Existing XV will close in case of HH level of Holding Tank (I-012).

 

mm217,

 

As per my understanding both of two consecutive XVs, with different failure mode, will be closed in case of HH level in holding tank. Am i right?

Fallah;

 

It gets a little confusing...

In existing design (as attached) because of solenoid the xv could not be F.O and it should be revised to F.C.

Off course in case of HH level XV valves should be closed. But in case of failure of instrument air flow, we might prefer to maintain XV open. In existing drawing with one XV it could not be possible.

We should consider another valve upstream XV-50RH001 (and remove solenoid from XV-50RH001- may be it is better to change the XV to control valve. then consider this valve as FO) but for the new XV which is closed in case of HH level the failure mode will be FC.

The question is: Is it logical to have two consecutive valve with different failure mode?

[fallah]

mm217,

 

A general response to your general question as last sentense of your previous post is: Normally no.

 

But the main issue is that you decided to change a shut down valve to a control valve just by removing relevant solenoid valve and it is not possible.

 

Anyway the failure mode of the XV should be "closed" and if you don't want the existing XV not to be closed due to IA failure, my recommendation to solve your problem is considering IA bottle(s) connected to solenoid inlet line as a back up in IA failure case.

 

 

[mm217]

mm217,

 

A general response to your general question as last sentense of your previous post is: Normally no.

 

But the main issue is that you decided to change a shut down valve to a control valve just by removing relevant solenoid valve and it is not possible.

 

Anyway the failure mode of the XV should be "closed" and if you don't want the existing XV not to be closed due to IA failure, my recommendation to solve your problem is considering IA bottle(s) connected to solenoid inlet line as a back up in IA failure case.

Dear Fallah;

 

I appreciate for your kind guidance.

I think you are right. 

 

Regards;