Influence of Humid Air Temperature on Friction Behavior in Pneumatic Cylinder

In the air, water vapor always exists and impacts directly on the friction surface between the piston rod and the rod seal. Water vapor in the air forms moisture film on the surface of the piston rod. In some cases, it plays a role as a lubricant. In general, to evaluate the amount of water vapor in the air, we use two measuring quantities that are relative humidity and absolute humidity. Although the relative humidity is equal at different temperatures, the amount of water vapor in the air is not the same and can be determined by absolute humidity. The paper presents the results of research on the effect of humid air temperature on the frictional behavior of the piston rod and a rod seal, under constant relative humidity conditions. The studies were conducted at a temperature of 150C, 320C, and 490C, with velocities of 5, 10, 30, 50, and 100 mm/s, respectively. The results show that the friction between the piston rod and rod seal (including a maximum force of static friction - FS and dynamic friction-FD) changes according to the ambient temperature of the humid air. When the temperature increases from 150C to 490C, the friction force decreases approximately 10 - 18%. The change in maximum force static friction is 1.2 times greater than dynamic friction force.