【Chemical Process Operations】Issues related to cross-contamination in pipelines
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This post was last edited by Xiao Gong 1985 on 2016-3-7 at 10:55. The design pressure for nitrogen is 0.6 MPa, and check valves are installed at the interfaces of the utility station; the design pressure for air is also 0.6 MPa, but no check valves are present at those interfaces. If there is an internal leak in the check valve for nitrogen, could air possibly flow back into the nitrogen stream during the process of purging the pipelines with both nitrogen and air? What is the reason for this?
It shouldn’t, first because the pressure is the same, and second because nitrogen has a one-way valve
Even with check valves, it is not possible to guarantee that material cross-contamination will not occur due to valve wear; it is recommended to install 8-shaped blind flanges on these utility systems when they are not in use.
Air may also enter the nitrogen pipeline network, and nitrogen may also enter the air pipeline network, due to 1. unreliable check valves. 2. Pressure changes occur in two types of medium pipeline networks during operation and use.
It is recommended to use blind flanges, as check valves cannot provide a complete seal.