An important factor affecting the flange seal is that the pre-tightening force must compress the washer to achieve the initial seal. Appropriately increasing the pre-tightening force of the Bolt can increase the sealing capacity of the washer. If the force is increased, the gasket can maintain a large contact surface pressure under normal conditions, but the force will not be too large. Otherwise, the whole gasket will lose its elasticity. Press and press the gasket, the acting force should be applied to the washer as evenly as possible. Generally, the diameter of the bolt is reduced and the number of bolts is increased. What are the specific factors that affect the sealing performance of the flange?
1. Gasket performance
Gasket is an important part of sealing for sealing the gap between two flange sealing surfaces and preventing fluid leakage, the type of gasket containing non-metallic gasket and metal gasket in order to enlarge the distance between gasket surface and flange sealing surface, in order to make the gasket surface and flange surface elastic, necessary elastic deformation needs to be generated under appropriate force. When selecting gasket materials, the working medium and working temperature should be considered. The width of gasket is also one of the important factors affecting the sealing.
2. Sealing surface type
The contact surface that plays a sealing role with Flange gasket is called flange sealing surface or pressing surface. The selection of sealing surface type is related to Shell, leakage result and gasket performance, the shape and surface properties of the flange sealing surface play an important role in sealing the straightness of the flange sealing surface and the verticality between the sealing surface and the middle line of the flange, the stress uniformity of gasket and the roughness of flange sealing surface with good contact between gasket and flange should be directly affected to meet the requirements of gasket.
3. Flange rigidity
Excessive warpage deformation caused by insufficient flange rigidity is mostly one of the main reasons for poor fastening and sealing of Bolt flanges in actual production. High rigidity flange deformation is small, the force of the bolt can be evenly transmitted to the washer. The rigidity of the flange is related to various factors. Among them, the thickness of the flange is appropriately increased by flange ring, the diameter of the middle circle of the bolt is reduced, and the outer diameter is increased by flange ring, in addition, increasing the size of the tapered neck can increase the bending resistance of the flange, but in principle, if the rigidity of the flange is not improved, the rigidity of the flange will be increased.
4. Control conditions
The influence of pressure, temperature and physical and chemical properties of medium on the sealing performance is complex. Simple pressure and medium have little influence on the sealing performance, but under the combined action of temperature, especially under the fluctuating high temperature, the sealing performance is seriously affected and fails due to fatigue. At high temperature, the medium has small viscosity, high permeability and is easy to leak. The corrosion effect of medium on gasket and flange is intensified, and the possibility of leakage is increased. Therefore, flange, bolts and gaskets produce large high temperature creep and stress relaxation, destroying the seal.