The Challenge
Pipeline pigging and slug catcher modeling have been a very difficult challenge for long long time. Now thanks to VMG, we can model pipeline pigging very easily in VMG Dynamic Simulation.
The Solution
In this example, we have a pig launcher, a pipeline, a flow control valve, a pig receiver and a slug catcher. The slug catcher is a horizontal vessel, 500 ft long with a diameter of 3 ft. The pipeline is 22,000 ft long with a diameter of 20". The pipeline profile can be found in this table.
Currently the pipeline has a total holdup liquid volume of 8215 ft3 and the slug catcher liquid level is about 4%. Since what comes in the slug catcher is almost the same as what goes out, the liquid level remains fairly constant. Now let us launch the pig in the pig launcher.
Dynamic Simulation
The pink line is the pig location. After about 2000 seconds, it is received in the pig receiver. The red line is the liquid goes to the slug catcher. As the pig moves along the pipeline, more and more liquid flows to the slug catcher. After the pigging is finished, the flow to the slug catcher almost drops to 0 and then it slows goes back to its normal rate. The green line is liquid flowing out the slug catcher and it remains fairly constant. The black line is the slug catcher liquid level. At the end of the pigging process, the slug catcher liquid level reaches its highest point and then it starts to drop. The blue line is the liquid holdup in the pipeline. it seems at about 8000 seconds, the pipeline liquid holdup reaches its high point again. It is a sign that we can relaunch the pigging process.
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