5 replies to this topic

[eby75]

I drying a pipeline 120km long by vacuum process. Its assummed that there is pockets of water in the line apart from the water film around the pipe wall. The average pipeline temp is 30 C. Is it possible to get different dew point reading at diffent sections of the line even though the vacuum pressure is same. Say the pressure is 4mbar but the dew point reading at 2km is -13 and 10km is -20

[Srikrishna Chaitanya]

Hi
practically its quite possible to have different water amounts at different locations of such a big pipe line . Dew point instrument reading depends on water content ( If I am not wrong ) at the measuring location , so Its quite possible to have diff dew point readings at diff locations of a same pipe line . I Presume Vacuum is being applied at one end of pipe line , If so its not mandatory to have same vacuum through out the length of the pipe .At one end where it connected to vacuum device we will see a high vacuum at other end we will see a min vacuum
Hope this helps
Regards,
Satish

[eby75]

I do agree with you veteran that there could be different dew point reading at different location depending on the water content but would then the absolut pressure reading be the same or different

[Srikrishna Chaitanya]

Hi Dear,

I hope you are asking for the pressure inside pipe when Vacuum is being applied. This pressure depends on Vacuum source in use & mainly its location . Here two cases are possible
1.Open system: One end of pipe is connected to vacuum source & other end is open or connected to some flow source .This case Pressure in the pipe will always be greater than Pressure at the vacuum source (Vacuum pump suction etc.). And you will have pressure profile in the pipe line
2.Closed System : One end of pipe is connected to Vacuum source & other end is closed . In this case the moment pipe is opened to vacuum source pressure in the pipe will not be uniform . After some time which depends on capacity of vacuum device / volume of pipe , pressure in the pipe will become uniform and ideally it reaches the vacuum developed by vacuum device .
If your system is 1) then pressure is different , If 2) The pressure is same

[eby75]

thank you satish, my system is closed hence the dew point temperature should be also the same when the pressure is the same

[Srikrishna Chaitanya]

Dear

Dew point is a function of pressure & water content both , change in any variable can change dew point .