Many of today’s sophisticated construction and oilfield hydraulic systems utilize servo controlled Piston style hydraulic pumps.
These servo’s are mounted on the pump and use an electric signal to port servo or pilot pressure to stroke the pump to a desired position in order to obtain optimum flow and pressure.
These valves are extremely dirt sensitive and when contaminated will cause a perfectly normal pump to perform as if it is no longer capable of producing optimum flow or pressure. As the problem may appear to be a general pump failure and not a specific servo problem the complete pump will often be sent in for repair.
When the repair facility evaluates the pump they are bound to rebuild it to function at factory new specs up to their stated warranty period which may be 12 months depending on the shop. Therefore the repair shop will replace or rebuild any components which may possibly fail during the warranty period; not just the offending servo.
So a pump that failed due to a contaminated servo valve which may cost between $500.00 and $1,200.00 to replace new could cost upwards of $5,000.00 to rebuild.
Obviously this is just the tip of the iceberg as downtime can be a much greater expense than the repair.
Rubber and metal particles from a seemingly innocuous “NEW” hose assembly can foul a servo immediately and put a piece of equipment on the maintenance board for a week to 10 days unnecessarily. New hose assemblies are contaminated and must be cleaned properly in order to protect expensive downstream components.