Hello All,

Subject of Discussions :
Differences in Temperature within a piping system of 3 parallel lines connected together with 1 line working at a time and other 2 lines having stagnant fluid withtendency to have cooler or hotter ambient temp.
.
Service : Crude Oil
Pipeline condition : vertically laid outdoor & uninsulated
Temperature Condition :
Service temperature = +65°C
Min. metal temp. = minus 3°C (ambient condition)
Installation temperature = +21.1°C
Max.metal temperature = +85°C
(due to Solar radiation)

We have a specific case as furnished below :

3 vertical riser pipes of 3 different pipe sizes of 6”, 8” & 10” are connected to a header of 20” both inlet and outlet of risers. The header at the outlet of riser is connected to inlet nozzle of a storage tank.
All the 3 riser pipes are carrying same crude oil of different flow rates with same operating pressure & temperature of 65°C. At operating condition as well as during shut down, (3 risers being outdoor & un-insulated), the metal temperature may rise to 85°C due to solar radiation. The design minimum metal temperature is furnished as -3°C. (Calculated from minimum predicted ambient temperature from 100 Yrs data)

The issue is “at a time only 1 riser will be used depending on the crude flow available and the other 2 risers will be closed through upstream valves. Since near the header at the outlet of the risers, there is no valve to isolate the risers from each other, all the 3 risers will be flooded with crude oil of operating temperature 65°C. when only 1 no. riser in operation and other 2 risers will contain stagnant fluid since there is no isolation from the line in operation.

Our query is :

“Is it that we require to analyze this piping system with temperature profile of running riser that of operating temperature of 65°C ,while other two riser pipes carrying stagnant fluid with temperature profile of far less temperature like minimum metal temperature of -3°C / maximum metal temperature +85°C because of the fact that the stagnant fluid may may tend to cool down or heat up the 2 riser lines by the direct influence of ambient temperature even though both the risers are connected open to the running riser carrying crude oil of 65°C.
or

“We analyse all the 3 risers exposed to same temp. condition - be it ambient max. (due to solar radiation), be it operating temp. , be it installation temp. , or be it exposed to minimum metal temp. of the ambient condition and analyse the thermal displacement from one temp. condition to other temp. condition or any other combination of these temp. conditions to be analyzed.”

Please Clarify as early as possible.

Thanks,
P.Manivannan.
Piping Design Engineer,
HEISCO, Kuwait,