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Pressure Reduction By Restricted Orfice


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#1 Ranga v

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Posted 28 August 2020 - 05:30 AM

From 18 " pipe line having working pressure 16.5 bar ,tapping of 3" is to be taken which is connected to another network.

 

Pressure & flow requirement at 3" pipe line are 60 m3/hr & 8 bar.Can a orifice be provided to kill the pressure ?  



#2 Ranga v

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Posted 28 August 2020 - 05:32 AM

The process fluid is condensate at 36 deg C ...forget to add



#3 Chemitofreak

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Posted 28 August 2020 - 06:17 AM

Yes, one can very much use a RO for killing pressure.

 

Please note that you need to carry out proper hydraulics to ensure that 60 m3/hr flows through the 3" piping. 

 

Tip:

 

If the fluid flowing through the piping is liquid, you have to note that there will be quite a pressure drop if 60 m3/hr liquid flows through 3" piping  



#4 breizh

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Posted 28 August 2020 - 08:48 AM

Hi,

Yes it will work ! As stated you need to perform the full hydraulic calculation ( orifice + line +fittings ) to get 8 barg at the discharge of your pipe . 

Good luck

Breizh 



#5 Bobby Strain

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Posted 28 August 2020 - 09:20 AM

You probably have not revealed the requirements for the flow through the 3" connection.

 

Bobby



#6 latexman

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Posted 28 August 2020 - 09:46 AM

Just be aware that if flow is slowed significantly or stopped downstream of the orifice, the pressure will increase to 16.5  barg on the downstream pipe and fittings.


Edited by latexman, 28 August 2020 - 01:27 PM.


#7 Pilesar

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Posted 28 August 2020 - 12:58 PM

A restricting orifice is useful to restrict flow rate, but is not suitable to control pressure. While it would provide pressure drop when there is flow, the pressure upstream and downstream of the orifice would equalize to the source pressure of 16.5 bar whenever the flow is stopped downstream of the orifice. A restricting orifice should not be used as a spec break for purposes of equipment pressure rating.



#8 Ranga v

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Posted 29 August 2020 - 03:04 AM

Sir

Flow requirement in 3" will be lined up in case of the failure of flow through regular line.8 bar is pressure at the 3" connection.

So it is like a stand by arrangement.

 

RO size was calculated Do it comes out be 33 MM but  velocity through Ro is 19 m/sec , is it acceptable??



#9 Bobby Strain

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Posted 29 August 2020 - 09:05 AM

None of this makes any sense to me. And you provide no information so that we might give a reasonable response.

 

Bobby



#10 Chemitofreak

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Posted 30 August 2020 - 02:38 AM

I agree with Bobby, you have provided insufficient information for members to comment.

 

We don't know the fluid that is flowing, in the later post you specify that this is a standby arrangement.

 

I would suggest you to write a brief about the system for us to help you.

 

Thanks



#11 Jiten_process

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Posted 30 August 2020 - 03:56 AM

A general answer to your question in absence of detailed info is, if your flow requirement is stringent than you have to employ a control valve. A restriction orifice can be used with careful design consideration. however, it can not ensure constant flow in fluctuation/upset in process conditions upstream/downstream or change in fluid properties e.g. mol wt, etc. 



#12 fallah

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Posted 30 August 2020 - 11:32 PM

From 18 " pipe line having working pressure 16.5 bar ,tapping of 3" is to be taken which is connected to another network.

 

Pressure & flow requirement at 3" pipe line are 60 m3/hr & 8 bar.Can a orifice be provided to kill the pressure ?  

 

Hi,

 

In general and at a steady state and fixed conditions in 18" line; yes, a RO might provide the required flow and pressure in 3" line. It's obvious RO cannot provide such flow and pressure at all with pressure fluctuation in 18" line or at downstream of 3" line. Hence, supposing the fixed conditions in 18" line and at downstream of 3" line, you should do the following evaluations to know if it's possible having required flow and pressure in 3" line:

 

1- Perform a hydraulic calculation for 60 m3/hr in 3" line to know if the velocity and pressure drop in mentioned line is within acceptable range.

2- Perform a flash calculation from 16.5 barg to 8 barg to know if two phase flow will be possible due to such pressure drop.

 

Then if there would be no problem in hydraulic conditions based on items 1 (velocity and P within acceptable range) and 2 (no two phase flow due to 8.5 bar pressure drop); you can size the RO based on 8.5 bar pressure drop and 60 m3/hr flow rate.



#13 Ranga v

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Posted 04 September 2020 - 09:06 AM

 For better clarity have attached is the PFD ,BFW pump cavitates whenever steam turbine due to vapour in pump suction.To avoid this condensate flow is maintained through bypass line into BFW suction. To maintain 8.5 kg/cm2 at the suction whats the engineering option.Line size 3" or 4" can be considered.

Can orifice be used for pressure drop of 6 kg/cm2g 



#14 Ranga v

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Posted 04 September 2020 - 09:10 AM

Find attached PFD....

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