Examination of in-service O-rings to determine extent of condition and remaining serviceable lifespan

Three fluoro-carbon based synthetic rubber O-rings were taken from cycle opposed piston engines. The O-rings have been in-service since 1994. The engines are utilized as Emergency Diesel Generators (EDGs); they supply on-site AC power during Loss of Power accidents. These O-rings are supplied as part of the Cylinder Liner Assembly which surrounds the cylinder/combustion chamber. The purpose of the O-rings is to separate the cooling water that surrounds the engine cylinder from the inlet air, exhaust, and lube oil of the engine. These O-rings are vital to the operation as leaks in Jacket Cooling Water could have significant consequences. Currently the Owners group for these engines recommends replacement of these O-rings at a 15-20 year interval. The objective of this work was to assess the condition of the O-rings and determine their level of aging. This assessment included a recommended remaining serviceable lifespan of the sample O-rings. The O-rings' dimensions, hardness, density, mechanical properties such as tensile strength, elongation at break and compressive strength, and formulation were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Using this data and historical operating information, a determination of the O-rings' condition and serviceable lifespan was produced.