9 replies to this topic

[PSilvy]

Hi, please i´m looking for advice in the following design problem:

 

In a CWR (cooling water return) line there is a temperature control valve (cooling water flow control) in function of gas outlet temperature. The pressure of CWR in header of cooling tower is highest that tower design pressure, so we have to install some pressure regulator device. 

 

The question is: there is any interference in the normal operation of control valve, if downstream other element are control pressure?

 

Best regards and thanks a lot by your comments. 

[breizh]

Hi pameliz ,

 

At the discharge point (outlet of the header) the pressure should be the same than the entrance of the cooling tower , close to atmospherical pressure.

 

Breizh

Edited by breizh, 07 May 2016 - 01:42 AM.

[fallah]

 

In a CWR (cooling water return) line there is a temperature control valve (cooling water flow control) in function of gas outlet temperature. The pressure of CWR in header of cooling tower is highest that tower design pressure, so we have to install some pressure regulator device. 

 

The question is: there is any interference in the normal operation of control valve, if downstream other element are control pressure?

 

 

pameliz,

 

Please upload a simple sketch of the system you described; it's more helpful to understand than the description...
 

[PSilvy]

 

 

In a CWR (cooling water return) line there is a temperature control valve (cooling water flow control) in function of gas outlet temperature. The pressure of CWR in header of cooling tower is highest that tower design pressure, so we have to install some pressure regulator device. 

 

The question is: there is any interference in the normal operation of control valve, if downstream other element are control pressure?

 

 

pameliz,

 

Please upload a simple sketch of the system you described; it's more helpful to understand than the description...
 

 

Thanks fallah, in attachments, there is a simple sketch. The CW is used in various equipments and the CWR is feeded to one tower (with 4 modules, but one basin). TCV is controlling flow according to required temperature in HEX´s process. Outlet pressure available in CWR is too high for tower (for pressure design) so we have to reduce. CWR flow is not constant, so, a pressure regulator, downstream, ¿will interference with flow controlled by TCV?  Sin título.pdf   5.48KB   29 downloads

 

BR

[Mahdi1980]

PSilvy

The pressure regulator does not interfere with the TCV.

However, as per your sketch the Temperature of all HXs are controlled by just one control valve?!!!!!!!

It is wonderful and impossible.

The temperature of the process for each heat exchanger to be controlled separately by a TCV located on the relevant CWR pipeline.

If your sketch is correct, it is a big fault in design.

 

Mahdi

[breizh]

Hi pameliz ,

 

You may consider the excelsheet attached to support your work and the analysis of the system .

 

This document belongs to Steve Hall , one of the great contributor in Chem eng .

 

Hope this helps

 

Breizh

Edited by breizh, 08 May 2016 - 02:52 AM.

[fallah]

 

Thanks fallah, in attachments, there is a simple sketch. The CW is used in various equipments and the CWR is feeded to one tower (with 4 modules, but one basin). TCV is controlling flow according to required temperature in HEX´s process. Outlet pressure available in CWR is too high for tower (for pressure design) so we have to reduce. CWR flow is not constant, so, a pressure regulator, downstream, ¿will interference with flow controlled by TCV?Sin título.pdf

PSilvy,

 

The pressure regulator (PCV) does interfere with the TCV...

 

In fact, the TCV will vary the flow passing to regulate the incompressible fluid temperature while at the same time the PCV will vary the flow passing through the same line to regulate the PCV back pressure and they might not be on the same track and have to fight each other to regulate their own variables...

[PSilvy]

PSilvy

The pressure regulator does not interfere with the TCV.

However, as per your sketch the Temperature of all HXs are controlled by just one control valve?!!!!!!!

It is wonderful and impossible.

The temperature of the process for each heat exchanger to be controlled separately by a TCV located on the relevant CWR pipeline.

If your sketch is correct, it is a big fault in design.

 

Mahdi

Thanks Mahdi, the sketch is just a rapid and very very conceptual representation of situation...my objective was represent TCV and PCV in the same line... 

 

My doubt is about some variation in flow derivated from PCV control and that flow variations go upstream, where TCV is controlling flow. And that variations, downstream TCV, produce some interference in temperature control.

 

BR

[PSilvy]

 

 

Thanks fallah, in attachments, there is a simple sketch. The CW is used in various equipments and the CWR is feeded to one tower (with 4 modules, but one basin). TCV is controlling flow according to required temperature in HEX´s process. Outlet pressure available in CWR is too high for tower (for pressure design) so we have to reduce. CWR flow is not constant, so, a pressure regulator, downstream, ¿will interference with flow controlled by TCV?Sin título.pdf

PSilvy,

 

The pressure regulator (PCV) does interfere with the TCV...

 

In fact, the TCV will vary the flow passing to regulate the incompressible fluid temperature while at the same time the PCV will vary the flow passing through the same line to regulate the PCV back pressure and they might not be on the same track and have to fight each other to regulate their own variables...

 

Ok, these was my first opinion, thanks a lot. 

Do you know or estimate some element that help with pressure decrease in tower inlet, for my case? without create a fight between TCV...O.R. (orifice restriction, an inicial alternative) was discarded because require a constant flow to do the job.

 

BR

[fallah]

 

Do you know or estimate some element that help with pressure decrease in tower inlet, for my case? without create a fight between TCV...O.R. (orifice restriction, an inicial alternative) was discarded because require a constant flow to do the job.

 

 

PSilvy,

 

If the tower is operating at atmospheric pressure, anyway the pressure at the tower inlet would be atmospheric; but if you want to decrease the flow within the allowable range for proper operation of TCV, You can use an restriction orifice at the TCV outlet....