Pressure pipeline
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The absorption tower is a atmospheric pressure tower. The equipment connected to the pump’s inlet and outlet is all at atmospheric pressure. There is a pressure of 0.5 MPa at the pump outlet. Experts say it’s a pressure pipeline. There is definitely pressure at the pump outlet; however, after the pump stops, the pressure returns to atmospheric pressure. All equipment connected to the outlet operates under atmospheric pressure. How should this be determined? The material in question is a Class C formaldehyde solution.
According to the definition of pressure pipelines as amended in Amendment No. 114 of the 2014 Version of the \"Catalogue of Special Equipment\": tubular devices that use a certain pressure to transport gases or liquids; such devices are defined as those with a maximum operating pressure of 0.1 MGAG or more, using gases, liquefied gases, steam, or liquids that are flammable, explosive, toxic, corrosive, and have a maximum operating temperature equal to or higher than their standard boiling point, and with a nominal diameter of 50 millimeters or more. Except for pipes with a nominal diameter of less than 150 millimeters and a maximum operating pressure of 1.6 MPaG, as well as the pipe bodies of equipment used to transport non-toxic, non-flammable, and non-corrosive gases.
When the pump is in operation, if there is a pressure of 0.5 MPa at the outlet, then that section of the pipeline is considered a pressurized pipeline. Even after the pump stops and the pressure drops to atmospheric level, the high-pressure condition during pump operation still requires management and maintenance in accordance with pressure pipeline regulations. Therefore, the experts’ judgment is correct; this section should be regarded as a pressure pipeline. .
Formaldehyde is toxic and falls under the category of pressure pipelines. Pipes with a diameter below DN50 are also not considered pressure pipes.
In this operating condition, pipes with a diameter ≥ DN50 are considered pressure pipelines.
The experts are right; it belongs to pressure pipelines
All pressure pipes are at atmospheric pressure after being shut down, but this does not change the fact that they are pressure pipes.