There are seven common reasons for vacuum flange leakage.
❶ Side mouth
Deviation refers to the pipeline not being perpendicular or concentric with the flange, and the flange surface not being parallel. When the internal medium pressure exceeds the load pressure of the gasket, flange leakage occurs. This situation is mainly caused during installation, construction, or maintenance, and is relatively easy to detect. By conducting a thorough inspection upon completion of the project, such accidents can be avoided.
❷ Incorrect statement
Misalignment refers to the situation where the pipeline and flange are perpendicular, but the two flanges are not concentric. The flange is not concentric, causing the surrounding bolts to be unable to freely penetrate the bolt holes. In the absence of other options, the only way is to enlarge the hole or insert a smaller bolt into the bolt hole, which will reduce the tension between the two flanges. And there is also a deviation in the sealing surface line, which makes it very easy for leakage to occur.
❸ Open your mouth
Opening the mouth refers to the excessive gap between the flanges. When the gap between flanges is too large and causes external loads, such as axial or bending loads, the gasket will be impacted or vibrated, losing its clamping force and gradually losing sealing energy, leading to failure.
❹ Wrong hole
Misalignment refers to the distance deviation between the bolt holes of the pipeline and flange that are concentric, but opposite to each other. Misalignment can cause stress on the bolt, and if this force is not eliminated, it will cause shear force on the bolt. Over time, the bolt will be cut off, resulting in seal failure.
❺ Influence of stress
When installing flanges, the docking of the two flanges is relatively standardized. However, in system production, when the pipeline enters the medium, it causes temperature changes in the pipeline, leading to expansion or deformation of the pipeline, which in turn causes the flange to be subjected to bending loads or shear forces, making it easy to cause gasket failure.
Corrosion impact
Due to the long-term erosion of the gasket by corrosive media, the gasket undergoes chemical changes. The corrosive medium penetrates into the gasket, causing it to become soft and lose its clamping force, resulting in flange leakage.
❼ Thermal expansion and contraction
Due to the thermal expansion and contraction of the fluid medium, bolts expand or contract, causing gaps in the gasket and allowing the medium to leak through pressure.
For pipelines with a design temperature of 300 ℃ or below and a nominal pressure less than or equal to 2.5MPa, flat welding flanges should be used. For pipelines with a design temperature greater than 300 ℃ or a nominal pressure greater than or equal to 4.0MPa, butt welding flanges should be used.
