Contact Bandwidth, Contact Pressure and Maintenance Practices

Poorly or improperly defined lapping criteria often leads to unsatisfactory variability in seat sealing performance. KEI used FEA to predict the stress intensity and contact pressure for several modeled seat band widths to help identify the root-cause, illustrate the importance of good maintenance practices, and help establish meaningful acceptance criteria for lapping.

The contact pressure and effective contact band width based on the initial lapped interface and elastic deformation of the seat due to seat load was predicted for a range of contact bands widths. The results are provided in Figure 2 and illustrate the importance of controlling the lapping process to achieve an optimal contact band width so that a robust seal – high contact stress over a sufficient width – is maintained.

Figure 1: FEA models and Stress Intensity

Figure 1: FEA models and Stress Intensity

 

Figure 2: The seat contact pressure and resulting band width for cases SC1, SC2, SC3 and SC4. The seat configuration of SC2 provides a good contact pressure over the contact band width; whereas, SC4 has a reduced contact pressure over a wider band width.

Figure 2: The seat contact pressure and resulting band width for cases SC1, SC2, SC3 and SC4. The seat configuration of SC2 provides a good contact pressure over the contact band width; whereas, SC4 has a reduced contact pressure over a wider band width.