Design pressure issues for vacuum vessels
Thread Content
The specified design pressure for vacuum vessels is difficult to understand, and the explanations provided by different people are quite confusing. For example, it isn’t clear what the external pressure involved in the design is, nor what the relationship is between this external pressure and the design pressure. Additionally, for jacketed vacuum vessels, the design pressure of the jacket shell should, according to regulations, be higher than 0.1 Mpa; yet some people have provided a value of -0.7 Mpa. It’s really confusing. Friends are welcome to discuss this, so that a reliable answer can be determined for everyone’s use.
Take 20570, for example: it refers to the design pressure for vacuum jacketed vessels. There are no examples for calculations, and various opinions exist regarding this topic. What exactly constitutes a design pressure that meets the regulations?
For example, in a vacuum jacketed vessel: the vessel body is under vacuum at 0.05 MPa, while the steam in the jacket is at 0.5 MPa. According to regulation 20570, the design pressure for the cylinder shell should be 0.1 MPa + 0.5 MPa = 0.6 MPa, while for the head without a jacket, it can be 0.1 MPa; for those with a jacket, it can be 0.5 MPa. But doesn’t a design pressure of 0.6 MPa for the vacuum vessel seem a bit strange?