Samples were evaluated and it was found after a thorough investigation that the ah290 humidification chambers can exhibit an internal water leak failure.In the presence of this failure, water can leak upstream from the water level regulating valves and cause flooding of the chamber; therefore, the reported failure was confirmed.The investigation identified several root causes that could contribute to a solvent bond failure and subsequent leak upstream from the water level regulating valves and causing flooding in the chamber of the device.The most probable root causes are related to dimensional change due to mold repair and process timing change due to scale up.Dimensional shift of frame cover id during mold repair caused weak solvent bonds by reducing/eliminating the interface between the tubing and frame cover needed for a robust solvent bond.Solvent bonding assembly steps did not mandate specific dip, hold, and cure times in the work instructions.Process drifted to shorter cure times leaking to weak or uncured solvent bonds.Solvent removal during the frame cover/water line blotting was difficult due to capped spikes (sealed tube didn¿t allow solvent to readily vacate the tubing id), leaking to excess solvent in the bond area.The uv potting operation can mask a poor or uncured solvent bond (weak, wet, or inadequate insertion depth during final inspection.Secondary and tertiary seals (two uv adhesive bonds) failed and did not provide robust back-up protection from leaks entering the chamber in the event of a solvent bond failure.The research and development team, technical lead, product engineering, and quality assurance worked on site with the supplier to implement corrective actions and to re-validate the production line.The frame cover mold was re-worked and re-validated with a tighter tolerance.The assembly process was updated to include specific dip, blot, and hold times during tubing installation and a 20-minute cure time has been added to ensure a complete and proper solvent bond.An additional leak inspection was added to the production line after the solvent cure time and prior to the uv adhesive potting operation to verify that the primary bond (solvent) is in-tact and passes leak inspection before it is capped off with the uv adhesive.A feature (wedge) was added between the frame cover and housing, forming a tapered mechanical seal to prevent the free flow of water into the chamber if the solvent bond and uv adhesive bonds fail.More stringent final leak inspection criteria were implemented and re-validated along with specific instructions to visually inspect for internal water leaks during the quality control inspections using water (destructive testing performed hourly.To verify effectiveness, product samples were produced with corrective and preventative actions and the manufacturing site.The samples were then shipped to the vyaire research and development facility for formal design verification testing.The design verification testing included variable cycle aging, shock-drop-vibration conditioning, and end-use simulation of product made with the minimum/nominal/maximum tolerance ranges for the tubing port.All testing passed, the supplier re-validated the assembly process.All validation are complete and verification tests all passed.
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