Flow rate after the nitrogen seal valve

After the nitrogen seal is installed, the flow velocity in the pipeline can be calculated based on compressed gases, using the calculation method for conditions of 0.3 MPa. .

Although the flow velocity remains roughly the same before and after nitrogen sealing, the gas is compressed in front of the valve, so a DN25 size is sufficient; at normal pressure behind the valve, a DN50–80 size is required. On site, many cans were seen on the nitrogen-purged pipelines; the diameters of the pipes before and after them are the same, which likely indicates a problem. When discussing this with different clients, some mentioned that the high nitrogen consumption makes it difficult to meet the KPI requirements. In some cases, the nitrogen sealing effect is not good. It is estimated that apart from quality issues with the valves, the choice of pipe diameter might be a contributing factor.

Indeed, multiple factors must be considered in the design of a nitrogen blanketing system. An improper selection of the pipe diameters before and after the valve can lead to increased nitrogen consumption or poor nitrogen sealing performance. Using DN25 before the valve is sufficient to meet the requirements of compressed gas, but when the pressure drops to atmospheric levels after the valve, the flow velocity decreases; therefore, a larger pipe diameter (DN50–80) is needed to ensure proper gas flow and dispersion. It is recommended to reevaluate the pipe diameter configuration of the existing system and discuss possible improvement options with professionals, such as changing the pipe diameters or optimizing valve design, in order to ensure the system’s cost-effectiveness and efficiency. At the same time, check for any air leaks or other issues in the system, as these can affect the effectiveness of the nitrogen seal and nitrogen consumption. .