Calculation of the vent pipe in the cut-off valve chamber
Thread Content
For a pipeline isolation valve room with a gas transmission main diameter of 1016 mm and a design pressure of 10 MPa, the standard specifies that the nominal diameter of the vent pipe should be DN350; but what should be the specific wall thickness?
For example, what is the wall thickness of the vent pipe for the West-to-East Gas Pipeline?
I haven’t done it. In my opinion, since it is in direct contact with the atmosphere and only subjected to a very small positive pressure, it is sufficient to use the standard STD wall thickness.
This falls under long-distance pipelines; you can understand it by looking at the formulas in ASME B31.8.
First of all, the original poster needs to know how long the blanking time is. Line isolation and venting are generally not as fast as the BDV at the station, and it is possible to manually control the opening degree of the valves in the venting pipeline. The pressure in the vent line is primarily determined by the backpressure applied. For example, if the vent pipe leads to the atmosphere at its end, the pressure can be considered to be 0 bar.g; the pressure at the starting point of the vent pipe is then determined by working backwards from the end point. In this way, you will know the design pressure of this vent line, and the wall thickness can then be calculated.