Performance Analysis of Radial Shaft Seals in Non-Stationary Rotational Movements

The number of applications involving rotational non-stationary movements has significantly increased in the past decade. Such dynamic rotational oscillations are often found in applications such as robotic arms. These dynamic rotational oscillations correspond to high levels of acceleration along with frequent changes in the direction of rotation. However, the impact of these oscillations on radial shaft seals (RSS) remains unknown. In practical applications, mineral oil has been found in undesirable situations, and previous studies suggested a potential correlation between these non-stationary movements and the buildup of vacuum in the intermediate cavity (the cavity between the dust lip and the sealing lip of an RSS). Therefore, this study aimed to bridge this knowledge gap by investigating the performance of an RSS operating under dynamic rotational oscillation and verifying the correlation between the vacuum pressure buildup and the occurrence of leakage. To explore various operational scenarios and assess the influence of each parameter variation on sealing performance, a set of experiments was designed. These experiments were conducted using the IWD Test Bench from MEGT. The IWD Test Bench consists of two test cells directly coupled to two servomotors, which can replicate dynamic rotational oscillation. Additionally, a prick device was developed to measure the pressure in the intermediate cavity with the aid of a pressure sensor and a medical needle. The tests were realized by varying the following parameters: (i) the acceleration at the sealing contact; (ii) the angle of oscillation; (iii) the degree of greasing in the intermediate cavity; and (iv) the type of curve performing the oscillation. The results showed the occurrence of leakage under certain circumstances, specifically with short oscillation angles, and photographs of the sealing contact indicated the occurrence of leakage concomitantly with the region of maximum negative pressure.