16 replies to this topic

[SyedAhmed]

Dear Friends

 

I have a question about Delay Time of Valves

How to set the delay time and 

Is there any of guidelines, codes & standards for the definition of delay time?

[paulhorth]

Syed,

Can you tell us what kind of valves you are talking about? and what their functions are?

 

Paul

[SyedAhmed]

Paul 

 

I am talking about the control on/off valve.

[thorium90]

The delay time as in the time the valve takes to fully close or open?

[paulhorth]

Syed,

Please make an effort to be more clear. A control valve is not the same as an on-off valve. An on-off valve is not the same as an ESD valve. The functions of these types of valve are different.So I repeat - what kind of valves are you talking about?

 

The delay time usually means a deliberate delay between the actuation signal and the start of valve movement . What Thorium mentions is the time for the valve movement AFTER the delay.

 

Paul

Edited by paulhorth, 13 August 2013 - 11:37 AM.

[SyedAhmed]

Paul

 

Sorry for the delay reply......

 

Actually In control philosophy I observed that ESDV delay time has been mentioned which is confusing without any standard reference....

 

As per my research the delay time is the time taken by the valve to open or close.

[gegio1960]

syed, paul definition is the right one.

[emd.franz]

Syed, 

 

If possible can you give the detail what kind of control valve (brand, model) you are pertaining to, And what is the nature of its work in your plant.

 

Regards,

 

Franz

[SyedAhmed]

Dear Franz

 

Actually, Its not a case, I found this in the cause and effect philosophy. Please read the post....

 

Regrds

Syed Ahmed

[paulhorth]

Syed,

It was you who mentioned control valves, in your post no. 3. It was you mentioned control philosophy in your post no. 6. You have never mentioned cause and effect philosophy before now. So don't criticise Franz, just tell us what the hell you are talking about, please.

 

Paul

[SyedAhmed]

Dear All 

 

Read the Post and Response accordingly....

[gegio1960]

Some points from my side:

1) I think you'll hardly obtain an answer if you don't clarify your question ;-)

2) what is the service of your valve? what is the signal causing the closure (or the opening, or the "stay in position") of the valve?

3) according to the rules of the forum, your email address shouldn't appear in the posts

Edited by gegio1960, 02 September 2013 - 03:02 AM.

[MJ94]

I think that he is asking about Emergency Shutdown Valves , after how much time will they close/ open when an interlock actuates...
egs we have three MOtor Operated vales to a reactor , at I/L ,O/L and a bypass , during a certain interlock action , I/L,O/L closes and bypass MOV Shutdown valve opens , the opening and closing sequence is : 1st the bypass MOV opens and then the I/L ,O/l close , 
Since it is a big Line the MOVs take to 3-5 secs for opening and closing .

Closing and opening time are such so as to not cause big jerks in the process.

 

[SyedAhmed]

As My post has the simple question that 

 

How to set the delay time and 

Is there any of guidelines, codes & standards for the definition of delay time?

 

MJ94 response:

big Line the MOVs take to 3-5 secs for opening and closing

Kindly mention the reference.

 

Gegio 1960 Response

what is the service of your valve? what is the signal causing the closure (or the opening, or the "stay in position") of the valve?

Please note that the service could be gas or any liquid so please mention the general reference literature to read. (As per post)

 

Regards

[gegio1960]

I'll try to answer you with an example (it seems you can't understand but maybe it's useful for other people)

 

- on/off valve service: fuel gas to heater burner

- cause signal: very low pressure of fuel gas network

- action of the signal: close the valve (& provide shutdown of the heater)

in this case you can put a delay of 30-60 s: you can wait this time before creating a dangerous situation and, in the meantime, the cause signal could cease. the delay allows to avoid the time consuming procedures needed to restart the heater.

 

there are specific guidelines covering particular cases but, generally speaking, the Process Engineer should decide what-to-do on the base of experience and knowledge of the process

[Zubair Exclaim]

I will give you another example .. a high pressure liquid transfer line from pumping  ... sudden closure of ESD can cause a pressure wave to generate and damage the upstream equipments and pump so a  delay time is used in closure of esd to allow for dissipation of pressure and then gradually bringing the ESD action ..

 

how to determine time ... best way  ... DYNAMIC SIMULATION ... not so best way ... > rule of thumbs

 

 

Any way guys keep the cool ... frustration doesnot make engineering tick

[fallah]

12345656,

 

Actually the delay time of an ESDV for which a value might be reflected in relevant C&E chart has nothing to do with the valve stroking time; i.e. the time between full open to full closed position. It refers to the time between getting interlock signal by valve and start of the interlock actuation in order to ignore the valve actuation if interlock signal would no longer be sustained due to, let say, a transient flactuation. An example may elaborate the matter:

 

Consider a SDV in a pump's suction will receive an interlock signal by LL level situation in upstream drum to be closed to prevent loss of inventory. A delay time for valve actuation due to such interlock could be considered because LL level might has been created following to a level flactuation and then may be removed within the delay time. Thus this would create an opportunity not having SDV closure and subsequent pump shut down...

 

As far as i know there is no specified code&standard for such delay time and it would depend on the system characteristics and is mostly specified based on relevant experiences in the similar previously operated facilities...

Edited by fallah, 02 April 2014 - 02:27 AM.