Fiber Optic Sensor System For Filament-Wound Pressure Vessels Available to Purchase

Filament-wound composite pressure vessels are used in the marine and transportation industries for storing breathing gases and gaseous fuels (SCUBA, firefighter, medical oxygen, CNG tanks, etc.). These tanks offer light weight, corrosion resistance, dimensional stability, and the ability to store significantly more air than an equivalent all metal tank. In the United States, use of these tanks is subject to Department of Transportation (DOT) approvals. To obtain DOT certification requires addressing the major issue of operational safety, as there is a much lower confidence level with composite tanks than with metal tanks. The fatigue mechanism in composite tanks that produces matrix cracking and eventual ply failures is more complex than for metal tanks. Another problem with composite tanks is the potential for external surface damage that comes from the kind of rough handling to which they are often subjected. For similar reasons, composite pressure tanks currently are manufactured under DOT Exemption, TC Regulation 3FCM in the United States. Safety is the key issue to be resolved for full certification of composite tanks. The ability to monitor structural integrity under a variety of operating conditions will be an important factor that determines tank recertification intervals and useful tank life. The interest in developing composite pressure tanks is here and the manufacturing technology is mature. What is needed, however, is a means of insuring that composite tanks are as safe to operate as metal tanks. This will facilitate DOT certification and appeal to consumers. This paper discusses a fiber optic sensor system embedded into the composite shell wall as a structural health monitor. Using a simple, low-cost optical fiber sensor, "smart" tanks can be checked easily for structural integrity each time the cylinder is refilled.