Degradation of Properties for GIS O-ring Seals Under Thermal-Compressive two-factor Accelerated Aging: Linear or Nonlinear?

The condition assessment and lifetime estimation methods of rubber O-ring seal used in gas-insulated metal-enclosed switchgear (GIS) has prospective significance. Previous research had built nonlinear models for the degradation of mechanical properties for O-rings, but this conflicted to the common-known linearity of oxygen consumption rate (OCR) which characterized the chemical aging rate. Perhaps this might be explained by the gradually losing of compressive stress, and the effort of this paper was to verify this explanation. In this paper, the thermal-compressive two-factor accelerated aging were conducted on GIS O-ring seals of two EPDM formulations. Determination methods of compression set (CS) and residual compression ratio (RCR) were proposed for GIS O-rings. The compression set at unit residual compression ratio (CSU) and its derivation (ARU) was derived. The results showed that CSU had good linearity with aging time and the trends of ARU was consistent with OCR, which verified the explanation.