How is the hydrostatic test pressure calculated when the inner tube of the jacketed tube is a vacuum tube?

Thread Content

The Construction and Acceptance Specifications for Jacketed Tubes SH3546 stipulate that the hydraulic test pressure for jacketed tubes shall be 1.5 times the higher of the design pressures of the inner and outer tubes, while the test pressure for vacuum tubes is 0.2 MPa. At the same time, the specifications also require compliance with SH3501. According to clause 8.1.5 c) of the 3501 pressure testing section, for pipes subjected to external pressure, the hydrostatic test pressure shall be 1.5 times the design internal and external pressure difference, and shall not be less than 0.2 MPa. I would like to ask my colleagues from Sichuan: when the inner tube of the jacketed tube is a vacuum tube with an operating pressure of -0.05 MPa and a design pressure of 0.1 MPa, and the outer tube of the jacket is made of steam with a design pressure of 0.63 MPa – all values being gauge pressures – how should the hydrostatic test pressure for the inner tube of this jacketed tube be calculated?