8 replies to this topic

[sushil singh]

Hi Everyone,

I am doing surge study for one of refinery pipeline. I have modelled the circuit in AFT Impulse. There are many TRV’s in the existing system.

I have considered the TRV’s (3/4 x 1” ) in the model. When I run the model the results shows surge pressure is well within the limit of  150# except TRV-3 inlet line.

So my question is whether we should consider TRV’s also in surge study.

Please refer attached sketch for better understandings

Your early responses will be highly appreciated.

[AlertO]

Hi sushil

 

i think TRV shouldn't be taken as a surge protection device as it is not designed for this application. Surge relief valve normally has specific features such as open quickly and then closes without slamming shut. To use the credit from TRVs propably leads to undersize of surge protecting devices.

 

Hope this helps.

[shawkat06]

Sushil,

 

Can you please attached the sketch?

 

Regards

 

Khan

[sushil singh]

Hi Alerto, 

Thanks for your reply

Hi Shawkat,

Sorry to attach sketch. Please find the attachment

 

 

Attached Files

•  Attachment.pdf   30.62KB   49 downloads

[fallah]

 

I have considered the TRV’s (3/4 x 1” ) in the model. When I run the model the results shows surge pressure is well within the limit of  150# except TRV-3 inlet line.

So my question is whether we should consider TRV’s also in surge study.

 

 

sushil singh,

 

Yes, you should consider inlet/oulet lines of TRV's in your surge study as these lines should have pressure rating can tolerate the surge pressure. Obviously, because of very low relief rate of TRV's and having no quick action against a pressure spike such as surge pressure, they cannot be considered as devices reducing the surge pressure...

Edited by fallah, 02 December 2015 - 01:10 AM.

[Alexsandres]

Dear Sushil Singh,

 

Currently I'm involved in one project for liquid transfer and surge issues. We do not consider TRV as a protection device during surge occur.

Relief load in TRV is very small compared to relief load generated during surge occur.

 

We provide surge dump valve as this equipment is designed as quick open.

 

This is my experience. If somebody have better description, it would be better to understand another reason. But, IMHO, TRV capacity would not cover required surge rate.

 

 

CMIIW.

[S.AHMAD]

http://www.iheating....rgereliever.pdf

[Shauno]

Several years ago, I completed extensive transient modeling of a 150 CL liquid propane loading system. Due to the nature of liquid propane, the system contained several TSVs and operated with a small margin between operating pressure and line class in hot ambient conditions. Similar to your case, most of the system experienced surge pressures in the model that were acceptable, however, on the 3/4"x1" TSV inlet lines, pressures were found to be well above the line rating in the model for certain transient scenarios.

 

I discussed the phenomenon with AFT several times and the discussions were inconclusive as to whether or not the surge pressures were "real" or just an anomaly in the model. The uncertainty was due to transient cavitation leading to modeled vapour being > 10 % of line volume in the TSV inlet lines which causes "non-physical peaks" in the model and can lead to unreliable results. As a result, we conducted field tests and determined that the surge pressures on the lines in question were "real" and we measured this using "tell-tale" pressure gauges that indicated maximum pressures encountered at specific locations in the plant. At the time, the field testing correlated very well with the AFT Impulse model. I've also done other Impulse modeling that correlated well with field data.

 

As these surge pressures could indeed occur, we actually replaced the TSV inlet lines with 300 CL piping to accommodate the potential surge pressures. We also utilized temporary overpressure allowances from ASME B31.3 to accommodate rare surge scenarios in which surge pressures would be above line design pressure but within the 133% of design.

 

I do remember scouring the web for any references to similar occurrences but didn't find much. Made me and others wonder if this was an area of transient modeling that could use further research as from what I recall, I think the high surge pressures are related to the PSVs opening due to surge pressures and then slamming shut very quickly. Of course, in the model, I had to make some assumptions around opening/closing times which I took from a Tyco/Anderson Greenwood reference.

 

So, in my opinion, you definitely want to account for the TSVs in your modeling and hopefully, some more research is done on this topic.

 

Hope this helps.

[56200358]

I am doing surge study for one pipeline. I have studied  a lot of resources about that but i dont know yet what criterion specially shall be considered. what is procedure and criteria for surge study(briefly)?

 

for example, design pressure for pipeline is 7barg. if there is pressure more than 7 barg in surge analysis, shall i consider PSV or surge tank? or pressure there should be more than 150 percent of design pressure to consider solution for that?(which number?design pressure or 50 percent more than design pressure?)

 

another question is applicaion of PSV and surge tank and difference between them in surge analysis. when we consider PSV and when consider surge tank for preventing of surge in pipeline?