Bi-composite surface texture configurations are proposed to study the friction performance of a mechanical seal under low speed. Three sets of comparative experiments were designed. They involved friction pairs with different pairing materials, single texture patterns, and bi-composite surface texture configurations. Tribological performances, such as friction coefficient, wear quantity, and surface topography, were measured. The research results showed that the average friction coefficient and surface temperature rise of the 3-C3 group (triangular texture in SSiC–conventional spiral groove in SSiC) were only 0.052 and 3.8 °C, respectively, which was the smallest friction coefficient and lowest temperature rise of all the test subjects. What’s more, the wear of M120D was mainly caused by the cutting effect of the texture edges, the adhesive wear of the non-textured areas, and the secondary wear caused by debris from the internal texture. It was indicated that the bi-composite patterns of spiral-triangle could produce a ‘synergistic effect’ by improving tribological performance and reaching lower friction in low-rotational-speed operation, which could provide a basis for designing a long-lasting and exceptionally reliable mechanical seal.

A dedicated test bench is employed to record acoustic emission signals from dry gas seals under various operating conditions. Time-domain and frequency-domain analysis methods are utilized to process and analyze the acoustic emission signals during start/stop, stable operation, and two common fault states (end-face defects and compensation spring failure). Furthermore, feature recognition research is conducted. A method for identifying the operational states of seals (low-speed friction, gradual detachment, stable operation) based on the root mean square (RMS) was established, with transition points at speeds of 100 and 1000 RPM, respectively. Additionally, spectral analysis is conducted using Fourier transform to determine the frequency band of acoustic emission signals (240–320 kHz) generated during contact wear of dry gas seals. Investigation into two typical faults of dry gas seals reveals that the RMS value of the acoustic emission signal gradually increases with the rotational speed during the operation of dry gas seal end-face defects. This is attributed to the insufficient dynamic pressure effect on the end face, resulting in long-term wear and tear. When the dry gas seal compensates for spring failure, the RMS value of the acoustic emission signal initially increases, then decreases, and finally increases again as the speed increases. It reaches the stable operating inflection point when the end-face speed is 800 r/min.

Purpose: This study aims to study the gas film stiffness of the spiral groove dry gas seal. Design/methodology/approach: The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals. First, a theoretical model of modified generalized Reynolds equation is derived with slipping effect of a micro gap for spiral groove gas seal. Second, the test technology examines micro-scale gas film vibration and stationary ring vibration to determine gas film stiffness by establishing a dynamic test system. Findings: An optimum value of the spiral angle and groove depth for improved gas film stiffness is clearly seen: the spiral angle is 1.34 rad (76.8º) and the groove depth is 1 × 10^–5 m. Moreover, it can be observed that optimal structural parameters can obtain higher gas film stiffness in the experiment. The average error between experiment and theory is less than 20%. Originality/value: The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals.