Problem with blowing liquid out of pipes
Thread Content
As shown in the diagram, the pipeline from the storage tank to its end is filled with liquid at a pressure of 3 kilograms. If nitrogen is used for purging by applying pressure at the purge port, with a maximum nitrogen pressure of 7 kilograms, can the liquid inside the DN150 pipeline at the end be completely purged using the control valve? The current situation is that the DN150 pipeline is 20 meters long, and the length from the purging port to the storage tank is 3 kilometers.
What is the medium inside the pipeline? Can it be discharged directly on site?
If this process is carried out by blowing into the tank, it won’t work.
If the location of the purge port is set incorrectly, how can the medium inside the DN150 pipeline be purged in the direction of the storage tank?
What is the future for this medium?
Then I can only say that it hasn’t been cleaned thoroughly; moreover, if it’s near the bottom of the storage tank, the static pressure difference of the liquid also needs to be taken into account.
Yes, in practice we are unable to achieve a thorough purge; the pipelines leading upstream are too long, and the back pressure is high.
The section from the purge port to the dead end of the pipeline definitely cannot be purged; why not purge from the end of the pipeline?
First, the pipe is under pressure; second, there is a blind flange at the end, so it’s impossible to open it when the pipe is under pressure and filled with material
For the final solution, we first used a diaphragm pump to pump the liquid in the upstream section of the pipe upward to the higher-pressure section; the pressure there, which was originally 1.4 kilograms, was reduced to almost zero. Next, the hose was lifted so that the end with the blind flange was above the horizontal section of the pipe. At this point, the blind flange was removed, and no liquid leakage occurred during this process; there was a slight negative pressure in the pipe. Then, a new blind flange equipped with a purge port was installed, and nitrogen was used to push air upstream from the end of the hose. During the purging process, laying the hose flat does not yield good results; the nitrogen in the tube moves upward from the liquid surface. By hanging the hose up, the liquid accumulates to form a sealed section, after which pressure is applied for further purging, and ultimately most of the material is pushed into the upstream piping.