The initial flange design is based on the process conditions. Once the material and type of the flange are selected, the standard initial dimensions for flanges are referenced. It's important to note that flange design calculations focus only on one component of the entire flange connection system. A complete flange connection involves three main parts: gasket design, bolt design, and flange body design, which are carried out sequentially. Any failure in one step can directly impact the next, making it essential to ensure accuracy at each stage. According to the WA-TERS method, the calculation process can be broken down into two key steps: a) determining the initial flange torque M0; b) calculating the various stresses under the flange moment M0.
In the optimized flange design, two criteria are simultaneously applied: the minimum load criterion and the full stress criterion. On one hand, the load applied to the flange—specifically the flange torque—should be as small as possible (minimum load), ensuring that the preloading torque and the operating torque are as close as possible (M1R2tf1R2fUMP). On the other hand, the stresses within the flange should be as close as possible to their respective allowable limits (full stress criterion), allowing for maximum utilization of the flange’s strength (as outlined in GB150122). This requires iterative calculations, adjusting certain parameters until the flange stresses are below the allowable values and remain balanced.
The following sections describe the design of the gasket, bolts, and flange body, adhering to the two optimization principles. Gasket design forms the foundation of the flange joint system. Based on the design conditions and the medium used, an appropriate gasket type and material are chosen, along with its size. The flange system must be evaluated in both pre-tightening and operational states to determine the required clamping force and flange moment, which are represented in terms of bolt load. The minimum bolt load required during pre-tightening is calculated as Wa = 3.14DGby, while the minimum bolt load during operation is given by Wp = 0.785D²Gp + 6.28DGbmp.
Three fundamental parameters define the gasket: y, the gasket specific pressure, which depends on the gasket material and thickness. Materials that deform easily have lower y values, and thicker gaskets tend to be more compressible, resulting in lower y values as well. m, the gasket factor, which relates to the material and shape of the gasket. Harder materials typically have higher m values. b, the effective sealing width of the gasket.
From the formulas for Wa and Wp, it becomes clear that reducing the value of b can decrease the clamping force. Therefore, in principle, a narrower gasket is preferred. However, if the gasket is only subjected to the bolt load during pre-tightening, excessive compression could lead to loss of sealing performance, causing instability. Thus, the gasket must have an appropriate width. If the designed width is insufficient, the compatibility between the bolts and gasket should be re-evaluated. Under the condition of ensuring reliable flange connection, the number of bolts can be reduced, or smaller specifications can be used, or a gasket with a larger y value and harder material can be selected to meet the requirements.
According to the minimum load principle, the clamping force required for the gasket should be minimized, meaning that Wa should be as close as possible to Wp in both pre-tightening and operating conditions. If Wa > Wp, it indicates that the gasket has a high y value and is too rigid. In such cases, a softer gasket with a lower y value should be used to reduce the pre-tightening clamping force. Conversely, if the gasket is too soft, a gasket with a higher y value and harder material may be necessary to meet the design requirements.
Integrated Temperature Transmitter
Integrated Temperature Transmitter,Thermocouple Transmitter,Rtd Transmitter,Temp Transmitter
Jiangsu Pinpai Technology Co., Ltd. , https://www.jspingpa.com