gas pipe inner wall temperature calculation
gas pipe inner wall temperature calculation
(OP)
Hi all
I need help. Quick response is highly appreciated. I am currently trying to solve one problem in on production platform. during the well start up gas cap from the well is being bleed off through the flowline manifold and main line to Separator. Gas temperature in well is 6deg C and pressure is 300barg. when gas passes to the separator through the choke valve its pressure drops to 26.5barg. due to joule Thomson effect the temperature drops down to -68 deg C.
In the winter the ambient temperature is -7 deg C.
The pipe embrittlement temperature is -51 deg C.
In reality I know that gas flow will not reduce pipe wall temperature to -68 deg C because of heat transfer from air. Also I know that pipe itself has some heat.
does any body knows how I can calculate pipe inner wall temperature? I have some more questions but it will be easier for me to ask when I have answer to this question.
Thanks a lot.
I need help. Quick response is highly appreciated. I am currently trying to solve one problem in on production platform. during the well start up gas cap from the well is being bleed off through the flowline manifold and main line to Separator. Gas temperature in well is 6deg C and pressure is 300barg. when gas passes to the separator through the choke valve its pressure drops to 26.5barg. due to joule Thomson effect the temperature drops down to -68 deg C.
In the winter the ambient temperature is -7 deg C.
The pipe embrittlement temperature is -51 deg C.
In reality I know that gas flow will not reduce pipe wall temperature to -68 deg C because of heat transfer from air. Also I know that pipe itself has some heat.
does any body knows how I can calculate pipe inner wall temperature? I have some more questions but it will be easier for me to ask when I have answer to this question.
Thanks a lot.





RE: gas pipe inner wall temperature calculation
With the correlations for the film coeficients inside and outside the pipe, it is possible to determine U, the global transmission coefficient and with U it is possible to calculate q.
When q and the film coefficient inside the pipe have been calculated you can calculate the inner pipe temperature.
RE: gas pipe inner wall temperature calculation
Keeping the flow below certain limit will limit temperature excursion - at least on paper. Please bear in mind that what happens in reality, and especially if there is liquid phase in the system, can be different from what the calculations say. It seems that the designer probably did not include cold startup in system design temperature calculations, and this can be potentially very dangerous thing. The system being on an offshore platform raises the risk further. Calculating the maximum flow that can prevent from overcooling is a good thing, but I wouldn't place my bets on that - there should have been a startup heater or a different piping class used.
Dejan IVANOVIC
Process Engineer, MSChE
RE: gas pipe inner wall temperature calculation
Bigger issue is probably hydrate formation. If you need to add meg upstream, it will throw your temp calcs all over the place.
Any calculation always seems to fall short of reality hence just control on temperature. Temp falls too far, reduce flow.
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RE: gas pipe inner wall temperature calculation
RE: gas pipe inner wall temperature calculation
RE: gas pipe inner wall temperature calculation
If you dont have the knowledge or the software i would recommend that you hire a consult for this type of work.
Best regards, Morten