Contamination between the spool and bore in valve assemblies can cause which failure?

Contamination between the spool and bore in valve assemblies can cause which failure?

• A. Bore enlargement
• B. Sealing loss
• C. Overheating
• D. Sticking

Answer: (A)

When foreign particles are present between the spool and its bore, they act as abrasives as the spool slides and shifts. This abrasive wear removes metal from the bore, enlarging its diameter over time. The broader bore changes the fit and clearance that the valve relies on for precise movement and sealing, so the internal clearance increases and the bore becomes oversized. That deterioration in the bore geometry directly leads to improper sealing and control, making bore enlargement the most direct failure cause from contamination at this interface.