What marking indicates that an O-ring is suitable for use with MIL-H-5606 (mineral base) fluid?

The marking indicating that an O-ring is suitable for use with MIL-H-5606 (mineral-based) fluid is a blue stripe or dot. This designation is crucial because it identifies materials that can withstand the chemical properties of the specific hydraulic fluid. MIL-H-5606 is a petroleum-based fluid, and not all O-ring materials are compatible with it. The blue marking serves as an industry standard to ensure safe and reliable use of components in hydraulic systems that utilize this type of fluid, preventing potential failures or leaks that could arise from using incompatible materials.

Understanding these color codes is essential for maintenance personnel and engineers, as using the correct O-ring not only ensures system integrity but also contributes to the overall safety of the aircraft or equipment utilizing these components.