The initial trial units of a fully sealed RSLED design failed after several weeks in-situ under water at a depth of approximately 3m. Design modifications to the RSLED head and further testing were carried out to enable permanent submersion at depths of up to 4m. Based on internal Nemalux testing, a fully encapsulated RSLED head appears water-tight and suitable for permanent submersion at depths of 4m or less. It should be noted that this is a Nemalux internal IP68 test only, and all units produced in this manner will be CSA or QPS special inspected to general location standards.
Several test units were built up fully encapsulated with QSil-216 silicone, in four different configurations to evaluate potential manufacturing processes. The configuration that will be used for future orders is outlined in a separate document, “RSLEDIP68 – Manufacturing Instructions”. The first test build had an unacceptable amount of trapped air, but test builds #2, #3, and #4 were successful.
After the silicone was allowed to completely cure, all four fixtures were put through a burn-in test of continuous operation at 110% of nominal power over 48hrs with data logging of thermal profiles. No abnormal conditions were observed, and burn-in testing was considered a pass.
To evaluate for water-tightness at depth, test units #2, #3, and #4 were placed in the dive pool at Adventures in Scuba in Calgary, AB. Pool depth at the test location was 4.2m, with fixture centres at 4m depth. Fixtures were submerged for 7 days before being removed for evaluation and further testing.
Once removed from the pool, the units were inspected for any visual evidence of water ingress, with no evidence found. Limited corrosion at the screw holes and at pre-existing scratches, and some blistering of the powder-coat was observed. These issues will be at least partially addressed by conversion coating of all components prior to powder-coating on production units. Water in the dive pool was heavily chlorinated, a highly corrosive environment. The units were taken back to Nemalux LED Lighting, and tested electrically. All units were found to be fully functional.
Submerged Power Cycling
After inspection and electrical testing, units were installed in a shallow tank with the highest point a minimum of 10” below waterline. The units were then electrically cycled on/off at 1-hour intervals for a minimum of 84 cycles (1 week) to subject the fixtures to multiple warm-up/cool-down cycles. If any water was present inside the fixtures the operating voltage should drive electrochemical corrosion and accelerate any failure. After power cycling underwater for 1 week, the fixtures were powered off and the tank allowed to cool to approx. 15°C over 24 hours. Units were removed from the test tank and checked out electrically with no problems.
After power cycling underwater was completed, the conditioned units were High-Potential tested to 400VDC continuous potential for 60sec. One unit failed due to an obvious manufacturing defect. The remaining units passed the 400VDC x 60sec Hi-Pot test.
Disassembly and final inspection of seal
Two test units were dismantled and inspected for water ingress visually and using Cobalt-Chloride water sensitive test strips. Both units were found to be completely dry, and devoid of any moisture. No cure inhibition was observed, indicating good chemical compatibility between QSil 216 and all internal components (MCPCB, wiring, cable gland, etc.)