How do lens rings achieve high gasket seat pressure with low bolt loads?

The lens ring's ability to achieve high gasket seat pressure with low bolt loads is primarily due to its design principles, material properties, processing requirements, and physical effects during operation. The cross-section of the lens gasket is designed to be spherical or similar to a convex lens. This design makes the contact between the gasket and the flange become a line contact instead of a surface contact. The line contact design significantly reduces the contact area, thereby producing higher local contact stress under the same bolt pretightening force, that is, achieving high gasket seat pressure. When the internal pressure of the system increases, the lens gasket will be affected by the internal pressure and expand radially. This expansion will further enhance the contact stress between the gasket and the flange surface, forming the so-called "self-tightening effect". This effect allows the lens gasket to maintain stable sealing performance in high-pressure environments with low initial bolt loads.
Lens gaskets are usually made of materials with good elasticity, such as metal, rubber or composite materials. These materials can elastically deform when subjected to external forces, filling the tiny gaps between flange surfaces to form an effective seal. At the same time, the elastic material can also adapt to the unevenness of the flange surface and improve the reliability of the seal. The hardness of the gasket material should be moderate. It should not only have sufficient strength to withstand the effect of bolt pretightening force and internal pressure of the system, but also avoid excessive contact stress with the flange surface and damage to the sealing surface. Generally, the gasket material should be softer than the flange material to allow for a tight fit with smaller bolt loads.
In order to ensure effective sealing between the lens gasket and the flange surface, the flange surface must have a high flatness. Any slight unevenness may cause the gasket to not fit tightly, thus affecting the sealing effect. Therefore, when processing flanges, it is necessary to strictly control geometric accuracy indicators such as flatness and parallelism. Lens gaskets usually need to be installed in the sealing groove of the flange. The machining accuracy of the sealing groove also directly affects the sealing effect of the gasket. The width, depth and shape of the sealing groove need to be accurately designed and processed according to the size and shape of the gasket.
Due to the line contact design of the lens gasket, when the bolt pretightening force acts on the gasket, stress concentration will occur on the contact line. This stress concentration helps achieve high shim seat pressure at smaller bolt loads. However, care needs to be taken to avoid excessive stress that could lead to damage to the gasket or flange. When the bolt pretightening force is released or the internal pressure of the system is reduced, the lens gasket can use its good elastic recovery ability to quickly return to its original shape and position, thereby maintaining the continuity and stability of the seal.
Lens gaskets achieve the goal of high gasket seat pressure at low bolt loads through a combination of unique design principles, material properties, processing requirements, and physical effects during operation. This characteristic makes lens gaskets have wide application prospects and important practical value in high-pressure pipeline systems and pressure vessels.