Smart Quantum Tunneling Composite Sensors to Monitor FKM and FFKM Seals

Abstract

Operators of industrial machinery relentlessly pursue improving safety, increasing productivity, and minimizing unplanned downtime. Elastomer seals are ubiquitous components of this machinery. In general, static seals are designed to be compressed at a fixed level of compression, taking gland geometry, loading condition, temperature range of operation, fluid media exposure, and other factors into account to ensure the safe operation of equipment. Over time, seals experience compression set, chemical-induced swelling, erosion, and other phenomena which can compromise the compressive force generated by the seal and cause leaking. This is particularly important in critical applications, where high pressure, high temperature, and aggressive media are present, and fluorinated elastomers are common materials for seals. Further, changes in operating conditions at manufacturing plants, either intentional or through regular process variation, create unknown operating conditions for seals. This unknown and variable application environment makes seal performance hard to predict. Therefore, machinery utilizing seals is, at best, serviced preventatively at certain intervals, where seals are removed, and the remaining useful life of the seal is unknown. This leads to unnecessary machinery downtime and increases consumable costs for manufacturers. In the worst case, the seal is run to failure, creating machinery and plant safety concerns. Both scenarios are undesirable for manufacturers using industrial machinery. This paper reports on the development of “smart” intrinsic self-sensing seals, which enable performance monitoring of the compression behavior of seals while in use. In addition, this paper examines quantum tunneling elastomeric composites (QTC) to demonstrate a method of component performance monitoring by modifying the underlying elastomeric material itself. This paper studies QTC sensor-based fluorinated (FKM) and per-fluorinated (FFKM) compositions, which are modified to incorporate varying levels of carbon nanostructure (CNS) material. The resulting seal’s resistive properties are shown to be a function of the level of compression, the first time this phenomenon has been demonstrated in high-performing FKM and FFKM seal materials.

A Review on Sensor‐Integrating Machine Elements

“…Cobb [151] filed a patent for a gasket with an enclosed load sensor, consisting of confronting electrodes, and a pressure sensitive electrically resistive material. A further method for detecting compression in rubber using either carbon fiber [152] or carbon nanostructure [153] filled rubber materials that change their conductivity when compressed or stretched. These materials were used to develop "smart" intrinsically self sensing seals (O-rings [153] and tubular seals [152] ) enabling the monitoring of compression levels.…”

“…A further method for detecting compression in rubber using either carbon fiber [152] or carbon nanostructure [153] filled rubber materials that change their conductivity when compressed or stretched. These materials were used to develop "smart" intrinsically self sensing seals (O-rings [153] and tubular seals [152] ) enabling the monitoring of compression levels. Using electrodes embedded in an O-ring, researchers were able to detect crevice corrosion in seawater piping.…”