Where: f friction coefficient, for PTFE seal ring, f=0.5, the friction torque of the valve stem in the packing depends on the sealing form and working pressure. When pressed, the upper and lower seal rings bear uniform pressure, and the friction in the packing does not depend on the rotation angle of the ball. Therefore, the friction torque of the packing is as follows: where: df valve stem diameter; H1 Contact height between single ring packing and valve rod; The friction torque of Z1 packing ring number valve stem head can be expressed in the following formula: where: the calculated diameters of dF and dFT valve stem heads can be seen from the above, and the opening and closing torque of pneumatic ball valves is determined by many aspects. For pneumatic ball valves with a diameter of 100mm and a pressure within 1.6MPa, the opening and closing torque cannot exceed 60N-M. From the above analysis, it can be seen that the floating pneumatic ball valve has its limitations. Due to structural reasons, the torque will increase exponentially under large diameter and high pressure. Therefore, it is necessary to select the pneumatic ball valve with fixed structure, and we will further explore its applicability.

The conductivity of industrial water and its aqueous solution is greater than 10-4 S/cm, the conductivity of acid, alkali and salt solution is 10-4~10-1 S/cm, and the conductivity of low degree distilled water is 10-5 S/cm. There is no problem with these uses. For example, if the conductivity of petroleum products and organic solvents is too low, they cannot be used. The water solution used may be proportioned with industrial water, and the conductivity will be slightly higher, which is conducive to flow measurement. The following figure lists the conductivity of several liquids at 20 ° C.