For valves connected by flanges, good insulation includes insulation of the whole flange and bolts. After overall insulation, the temperature of all parts (valve body, flange, bolts, etc.) of the valve is basically the same during operation. However, for the exposed valve, the temperature of the flange is higher than the bolt temperature during operation, and the expansion of the flange in the axial direction is greater than the expansion of the bolt, which causes an additional temperature stress on the axial direction of the bolt. The superposition of this temperature stress and the tensile stress generated when the bolt itself is tightened may cause the creep and yield of the bolt. When stopping, the bolt cannot return to its original length after the temperature decreases, so it will become loose, and it is easy to leak when starting again.

The pneumatic ball valve is mainly used in the flow pipeline for quick cutting off, distributing and changing the medium. The structure of pneumatic ball valve mainly has two types of structures: O type and V type ball core. The O type ball valve core is a floating precision casting, with the same diameter as the pipeline port, which is mainly used as a cut-off switch; The other is V-shaped ball core, which adopts a fixed structure, with V-shaped notch on the ball core. After the positioner is installed on the actuator, the proportion of fiber and granular media can be adjusted.