Which of the following is NOT a hydraulic contamination type?

• A. Water
• B. Organic solids
• C. Inorganic solids
• D. Metallic solids

Answer: (A)

In hydraulic systems, contaminants are often classified by their physical form. The three forms listed—organic solids, inorganic solids, and metallic solids—are all particulate contaminants that can be present in the fluid. Water, while a serious contaminant, is considered moisture rather than a particulate contamination type in this classification, so it doesn’t fit with the other three categories. Thus, water is the option that does not represent a hydraulic contamination type in this scheme. In practice, water can cause rust, corrosion, reduced lubrication, and cavitation, and is typically managed separately from particulate cleanliness classifications.