2.2.1. The Influence of Diaphragm Thickness

Contrastive displacement diagram (Figure 3) shows that with the decrease of diaphragm thickness, the maximum strain region increases gradually, the strain distribution is more uniform and the strain transmission is better. That is, the displacement input of valve stem can be well maintained to the surface of diaphragm, so that the diaphragm can produce a certain amount of deformation with the input requirements, and the runner can produce the corresponding opening. From this point of view, the thinner diaphragm is more conducive to the diaphragm valve flow accurate control. In addition, the thinner the diaphragm, the smoother the deformation at the bottom, the approximate planes at the maximum displacement, the larger the contact area with the top of the ridge, and the better the sealing performance.

However, this does not mean that the thinner the diaphragm, the better. Contrast stress diagram (Figure 3) shows that the thinner the diaphragm valve is, the greater the maximum stress is, and the greater the maximum stress area is, especially the upper and lower surface of the diaphragm. The thicker the diaphragm, the lower the stress is in most areas. The maximum stress is only concentrated in the sealing contact area of the diaphragm bottom surface, and sticks to the ridge top. After tightening, part of the stress is offset, which means that the possibility of diaphragm damage is reduced and the life of the diaphragm is longer.

(**a**) Cross-sectional diaphragm displacement (**left**) and stress (**right**) with *B*0 = 4 mm thickness

(**b**) Cross-sectional diaphragm displacement (**left**) and stress (**right**) with *B*0 = 5 mm thickness

(**c**) Cross-sectional diaphragm displacement (**left**) and stress (**right**) with *B*0 = 6 mm thickness

**Figure 3.** Displacement Diagram and Stress Diagram of Diaphragms with Different Thicknesses.
