5 replies to this topic

[Harshuch]

Hi,

 

I need to evaluate whether pressure equalization line is required across a particular ESD valve or not. Can you give me any leads as to in which documents I can find the required evaluation methodology? 

 

Regards,

Harshit

[fallah]

Hi,

 

If you mean by pass line as equalization line, it depends on the shut down level as follows:

 

For shut down level 3 (equipment shut down): Considering by pass is authorized

For shut down level 2 (unit shut down): Considering by pass is authorized but with CSC facility

For shut down level 1 (fire zone emergency shut down): Considering by pass isn't authorized

[Dazzler]

I think Harshuch is thinking of the case of say a large diameter main line valve for high pressure gas service needing a smaller bypass valve and line for use in pressuring up the downstream side prior to opening the main valve.  But I'm not sure of the criteria for ewhen it is/ is not recommended.  Looking forward to reading more.

Dazzer

Edited by Dazzler, 24 June 2013 - 11:04 PM.

[ashetty]

Normally depends on the Delta P & the main line size (>12" ?..I`m not sure). Check the worst case Delta P (ESD valve actuator is sized based on this).Going by personal experience i know that if Delta P is huge sometimes SDV has problems opening.There is also the possibility of a pressure surge resulting in line vibrations or downstream equipment damage. Check your project philosphy whether manual bypasses are permitted for your particular case (See Fallahs post above). Make sure the bypass valve is Locked closed. Also in case of long line pipes estimate the time required to pressurize the downstream segment and size your bypass line accordingly.

[fallah]

Dear All,

 

Please note that OP is particularly asking about the by pass valve across ESDV, then safety issues will come into play such that valve function/operation in a shut down case not to be affected by adding a by pass as a pressure equalization line facility...

 

In fact, as I mentioned in my previous post for ESDV (shut down level 1), considering by pass even as pressure equalization facility isn't authorized....

Edited by fallah, 26 June 2013 - 12:34 PM.

[Dazzler]

I agree that for some protective systems (ie ESD) a bypass is not permissable, however perhaps it is ok when the bypass valve ALSO was actuated to trip just like the main valve.  Then it could be ok.

Dazzler