3 replies to this topic

[roshimessi]

dEARS

 

one of the protection of the control valve due to fully open is using the PSV downstream of control valve based on control valve failure

but if we considered the restriction orifice ,does it need to put psv downstream of RO

as i know RO has constant bore and we do not have failure for RO,

Does any one have any experience

THANKS

[fallah]

Hi,

 

If there would be an isolation valve (or valves) at RO downstrinsteam, you have two options to protect downstream against overpressurizing by upstream:

 

1- Consider class break at downstream of the isolation valve (or downstream of the last valve), then the line before and after RO till downstream isolation valve will have the same pressure rating means due to closing the isolation valve the line between RO and isolation valve would be protected by System Design and no need to PSV for protection.

 

2- Consider class break at RO downstream, then the line between RO and valve should be protected by a PSV.

[shekhar dhuri]

Hi roshimessi,

First of all one needs to know if we use RO instead of control valve will the system work ? As we all know, control valves are used for controllability purpose whereas since RO has fixed bore diameter, flow through RO is fairly constant at constant upstream / downstream pressure. Once we are clear that by putting RO system will work, then instead of installing PSVs, it is practical to design system as explained below by Mr. Fallah.

Regards,
Shekhar Dhuri

[Jiten_process]

Hi shekhar,

 

Well, it is also important to mention the system you are dealing. is it a gas system or liquid or mixed phase. Is your system happens to be such that you need frequent turn down. 

 

As we all know, RO cannot be replaced by a control valve, is if is so no body would have used control valve and vice versa is also true. But the fact is both exists, ofcourse depending on application. 

 

coming back to your question whether RO can be used inplace of control valve. There is no fix answer yes or no. you need to analyze your system configuration and take a call. few are the good examples where RO is successfully used i.e. Pump recirculariton lines, few venting system, Nitrogen lines etc. so it depends on whether your system operates in continuous varying flow, or your system susceptible with respect to flow and pressure of the downstream flow stream. You also have to check the performance of the RO for all the possible flow/pressure condition. These are few of the criteria or questions which will give you answer whether you can use RO or NO, in place of control valve. 

 

Secondly, keep one thing in mind, PSV is an ultimate safety. PSV should not be replaced by any other means unless you have strong justification which i personally dont see in RO,  It is true that RO gives you fixed PD all the time and there is no failure, however, no body give you gurantee that RO will not clog by any foreign particle (be it rust or any solid).

 

In my opinion, it is not good to replace PSV, it will not save you much of the cost but will put you in question with respect safety aspects of a plant.

 

Call is yours...good luck.  

Edited by Jiten_process, 13 January 2014 - 04:19 AM.