The selection of gaskets usually depends on industry requirements or known flange standards to determine gasket standards. The power industry generally requires the use of Chinese national standards;
Determine the nominal diameter and nominal pressure of the gasket according to system requirements;
Determine the type, material, and model of the gasket based on the temperature, pressure, corrosion performance, and other requirements of the medium.
The processing quality of the flange, the amount of bolt thread insertion, the amount of flange rotation, the amount of bolt tension, the filling agent of the medium, and the surface treatment of the flange all affect the sealing effect of the gasket. Therefore, the selection of sealing gaskets should consider many factors, especially in the selection of gasket sealing materials. The variables appearing at the flange connection seem endless, and all these uncertain factors may affect the sealing effect of the gasket. It is necessary to comprehensively consider various parameters in order to make appropriate choices.
1. Media
There are thousands of fluids in the medium, and the corrosiveness, oxidation, and permeability of each fluid vary greatly. The materials must be selected according to these characteristics. In addition, the cleaning of the system must also be considered to prevent the erosion of the gasket by the cleaning solution.
2. Temperature
In most selection processes, the temperature of the fluid is the primary consideration. This will quickly narrow the selection range, especially from 200 ° F (95) to 1000 ° F (540). When the system operating temperature reaches the maximum continuous operating temperature limit of a specific gasket material, a higher level of material should be selected. This should also be the case in certain low-temperature conditions.
3. PT value
The so-called PT value is the product of pressure (P) and temperature (T). The pressure resistance of each gasket material varies at different temperatures and must be comprehensively considered. In general, the manufacturer of gaskets will provide the maximum PT value of the material.
4. Pressure
Each type of gasket has its highest ultimate pressure, and the pressure bearing performance of the gasket weakens with the increase of material thickness. The thinner the material, the greater the pressure bearing capacity. The selection must be based on the pressure of the fluid in the system. If the pressure often fluctuates violently, it is necessary to understand the detailed situation in order to make a choice.
5. Application
The most important parameters in application are the type of flange and the bolts used. The size, quantity, and grade of bolts in application determine the effective load. The effective area of compression is calculated based on the contact size of the gasket. The effective gasket sealing pressure can be obtained from the load on the bolt and the contact surface of the gasket. Without this parameter, it would be impossible to make the best choice among numerous materials.
In addition, before installing the gasket, it is necessary to clean the surface of the gasket and flange, check for scratches on the gasket surface, inspect the dimensions, materials, bolts, and other details of the gasket according to regulations, and strictly clean the surface of dirt. Before installation, make a judgment on the roughness of the flange surface and the parallelism of the sealing surface to see if it matches the type of gasket. The gasket shall be placed correctly during installation. In order to obtain more accurate bolt stress, Torque wrench and other auxiliary tools shall be used.