Is there a relationship between low-temperature operation and pressure in carbon steel pipelines?
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Our factory has medium-pressure nitrogen and low-pressure nitrogen, but there is an abundance of medium-pressure nitrogen while low-pressure nitrogen is in short supply. The current process setup involves using medium-pressure nitrogen (6.5 MPa) which is reduced to 0.4 MPa; frost formation occurs at the location downstream of the control valve due to the low temperature. If the temperature drops below -20 degrees Celsius, are there any safety issues at this pressure level?
If the pipeline is made of ordinary carbon steel, then -20°C is the lower limit for its operating temperature; at such low temperatures, the cold brittleness of ordinary carbon steel increases, making the pipeline more prone to breaking and other issues, thus posing a significant safety risk. It is recommended not to use ordinary carbon steel; instead, low-temperature carbon steel such as 16Mn should be used, with a minimum operating temperature of up to -40°C℃