Do pressure vessels with a negative design pressure value refer to vessels under external pressure or vacuum?

This post was last edited by huqihua2010 on 2010-4-20 at 10:44. A negative pressure system generally refers to a vessel under external pressure; the pressure in a vacuum vessel should be zero. The weights listed in the detailed specifications on the drawings are usually the theoretical weights obtained from reference tables. When providing a quote and calculating the cost, the weight of the raw material should be determined based on the usual requirements for material cutting.

Under extreme conditions, a vacuum vessel can be considered to have an absolute pressure of zero inside it, but it is still designed as a vessel that withstands external pressure.

The design pressure of the vacuum vessel is -0.1 MPa. By design pressure, we mean gauge pressure, not absolute pressure

1. Pressure vessels with a negative design pressure value refer to vessels under external pressure or in a vacuum state. Vessels under external pressure, such as inner cylinders with jackets, are subjected to external pressure; the design external pressure value can be taken as the jacket’s design pressure, and a negative value should be used in calculations. Vacuum vessels, such as buffer tanks or storage tanks during unloading, or certain towers and reactors, experience a vacuum inside due to rapid cooling, with this value ranging from 0 to 0.1 MPa (gauge pressure). 2. The weights of various components listed in the details sheet on the pressure vessel drawings refer to their actual net weights. Standard components such as flanges, lugs, end caps, and supports can be obtained directly from standards and filled in accordingly. It should be noted that the theoretical weights of these standard components specified in the standards generally refer to those of carbon steel; therefore, if stainless steel components are used, an adjustment is necessary. The calculation method is: theoretical weight of the component / 7.85 × 7.93.

There is a slight error; it should be a negative value. 1. Pressure vessels with a negative design pressure refer to vessels under external pressure or in a vacuum state. Vessels under external pressure, such as inner cylinders with jackets, are subjected to external pressure; the design external pressure value can be taken as the jacket’s design pressure, and a negative value should be used in calculations. Vacuum vessels, such as buffer tanks or storage tanks during unloading, or certain towers and reactors, experience a vacuum inside them due to rapid cooling, with values ranging from 0 to -0.1 MPa (gauge pressure).

I believe a container that generates an external pressure difference in a vacuum state is a vacuum container, whose pressure value does not exceed -0.1 Mpa. If external pressure is applied to seal it, the resulting pressure is known as external-pressure vessel; this pressure value can be greater than -0.1 Mpa or less than -0.1 Mpa.

GB150 specifies containers with a pressure rating of not less than 0.02 MPa

GB150 does not cover containers with a vacuum level below 0.02 Mpa

Is gauge pressure the pressure difference between the inside and outside? ? In that case, -0.1Mpa is understandable. But absolute pressure is generally used to measure the degree of compression on a container; if it is -0.1 Mpa, then no such place exists on Earth.

That is, it can be greater than 0.1 when under external pressure, while the maximum value in a vacuum condition is 0.1