Judgment of pressure pipelines with jacketing
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There is a welded exposed-type jacketed tube; the inner tube has a diameter of DN50, is made of 304 material, operates at a pressure of -0.098 MPag and a temperature of 200°C, with a fluid that belongs to category C. The outer tube has a diameter of DN80, is also made of 304 material, operates at a pressure of 0.7 MPag and a temperature of 280°C, with heat transfer oil as the fluid. May I ask, when determining pressure pipelines using jacketed pipes, are the inner and outer tubes evaluated separately? The inner tube is under negative pressure, but the outer tube is under positive pressure; then does the inner tube also experience external pressure, and should it be classified as a pressure pipeline as well?
Pressure pipelines are defined as those with a maximum operating pressure of ≥0.1 Mpa(G), and the inner and outer pipes should be defined and classified separately. 1. Only the operating pressure of the inner tube, -0.098 Mpa, is indicated. 2. The external pressure acting on the inner tube is not taken into account in the pressure definition
It mainly depends on the properties of the medium, the pipe diameter, and the operating pressure: 1. The inner pipe is not a pressure pipe; its diameter is appropriate, but the operating pressure is too high, exceeding 0.1 MPa; 2. The outer pipe is a pressure pipe used for transporting flammable liquids, and both its operating pressure and diameter are within the acceptable range