13 replies to this topic

[Estiqaatsi]

In what situations can it be useful or necessary to use a globe valve for an on / off service, as an isolation valve? The situation that I am dealing with is with valves installed on pipes downstream a steam condenser, I was expecting some ball or gate valve. Am I overlooking some obvious aspect?

Edited by Estiqaatsi, 02 November 2021 - 09:44 AM.

[Chemitofreak]

Never have I seen a globe valve used as a block valve.

[Bobby Strain]

Never is a loooong time!

 

Bobby

[fallah]

In what situations can it be useful or necessary to use a globe valve for an on / off service, as an isolation valve? The situation that I am dealing with is with valves installed on pipes downstream a steam condenser, I was expecting some ball or gate valve. Am I overlooking some obvious aspect?

 

Hi,

 

Please ensure about on/off service of the valve. In the same situations, downstream of steam condensation, generally a control valve will be installed to automatically adjust the condensate flow rate, say, based on the condensate level; but it might in your case this control valve (normally globe type) will do the job manually.

[Estiqaatsi]

 

In what situations can it be useful or necessary to use a globe valve for an on / off service, as an isolation valve? The situation that I am dealing with is with valves installed on pipes downstream a steam condenser, I was expecting some ball or gate valve. Am I overlooking some obvious aspect?

 

Hi,

 

Please ensure about on/off service of the valve. In the same situations, downstream of steam condensation, generally a control valve will be installed to automatically adjust the condensate flow rate, say, based on the condensate level; but it might in your case this control valve (normally globe type) will do the job manually.

 

 

Dear Fallah and other colleagues,

thank you for your answers.

 

As for the on/off service, it is what I have found in a valve list provided by the condenser supplier. It seemed strange to me too.

 

I'll describe more precisely the situation. It is a revamping of a steam air cooled condenser, where new modules are being added. So a new LP steam line starts from the old one to feed the new modules, and a new condensate line is then connected to the old one, downstream of the new modules. The manual valve is installed on this condensate line. So what I thought, looking at the P&ID, was that a manual globe valve would have been useful to "tune" the system (in addition to adjusting the fans speed during normal operation) and balance the flowrates.

Edited by Estiqaatsi, 03 November 2021 - 03:40 AM.

[fallah]

 

 

 

Dear Fallah and other colleagues,

thank you for your answers.

 

As for the on/off service, it is what I have found in a valve list provided by the condenser supplier. It seemed strange to me too.

 

I'll describe more precisely the situation. It is a revamping of a steam air cooled condenser, where new modules are being added. So a new LP steam line starts from the old one to feed the new modules, and a new condensate line is then connected to the old one, downstream of the new modules. The manual valve is installed on this condensate line. So what I thought, looking at the P&ID, was that a manual globe valve would have been useful to "tune" the system (in addition to adjusting the fans speed during normal operation) and balance the flowrates.

 

 

Hi, 

 

Please upload a simple sketch of the system you described for our info...

[Estiqaatsi]

 

 

 

 

Dear Fallah and other colleagues,

thank you for your answers.

 

As for the on/off service, it is what I have found in a valve list provided by the condenser supplier. It seemed strange to me too.

 

I'll describe more precisely the situation. It is a revamping of a steam air cooled condenser, where new modules are being added. So a new LP steam line starts from the old one to feed the new modules, and a new condensate line is then connected to the old one, downstream of the new modules. The manual valve is installed on this condensate line. So what I thought, looking at the P&ID, was that a manual globe valve would have been useful to "tune" the system (in addition to adjusting the fans speed during normal operation) and balance the flowrates.

 

 

Hi, 

 

Please upload a simple sketch of the system you described for our info...

 

 

 

https://ibb.co/dpq8QzM

[breizh]

Hi,

you may want to read what others said in another forum :

https://www.eng-tips....cfm?qid=301174

the answer seems to be it "depends " ! 

Breizh 

[latexman]

They could be for balancing the flows.

 

Something looks strange on the PFD.  The New Module top right outlet (gas/vapor) is going to condensate and the bottom right outlet (liquid) is going to non-condensibles.  It seems backwards 

[Estiqaatsi]

They could be for balancing the flows.

 

Something looks strange on the PFD.  The New Module top right outlet (gas/vapor) is going to condensate and the bottom right outlet (liquid) is going to non-condensibles.  It seems backwards 

 

sorry, the sketch was made quickly and I was not paying attention to top/bottom placement of the outlet lines. my point was the function of a globe valve installed both on the new condensate and the new non-condensables lines.

Edited by Estiqaatsi, 03 November 2021 - 01:28 PM.

[Bobby Strain]

Seems to me that the valve is only used for isolation. So, any type of valve should be satisfactory. Just needs to be tight shutoff. I presume that there is also a valve on the inlet to the new condenser.

 

But maybe the designer presumed that a throttling valve could be useful, (or necessary), in directing variable flow to the new condenser. You should talk with the designer. That's the only way you will reach a conclusion.

 

Bobby

[breizh]

Hi ,

You cannot perform service without installing valves at the inlet of the steam condensers ! 

You may have them installed ,not shown on the drawing . 

Breizh 

[Estiqaatsi]

Hi ,

You cannot perform service without installing valves at the inlet of the steam condensers ! 

You may have them installed ,not shown on the drawing . 

Breizh 

 

Actually I forgot to represent a spacer that they introduced in the new LP steam line (to isolate the new modules, I think, maybe when the weather is too cold; of course this can be made only when the plant is shut down).

Then there is a butterfly valve just downstream of the turbine, but it doesn't seem to be related with the condenser operation.

[breizh]

Hi,

If you go for shut down to perform maintenance you don't need isolation valves , this means that the glove valves are throttling valves to balance the streams between the two condensers . 

 

Breizh