🔍 Key Concepts

• Hydraulic unloading valve operation in a steering or power unit system • Relationship between replenishing pump flow, service tank, and pilot pressure to shift distributor valve "A" • Difference between centered (neutral) and shifted positions of a spool-type valve like "C"

💭 Think About

• On the diagram, when the port power unit starts, where does the initial replenishing pump flow try to go, and what would that do to system pressure if valve "C" stayed centered? • Look at the pilot lines running from the replenishing/servo pump toward distributor valve "A". How would shifting valve "C" change the pressure in those lines compared with sending flow directly back to the service tank? • Which answer choices describe building pilot pressure versus dumping flow to tank, and which side (port or starboard) of the system is each one talking about?

✅ Before You Answer

• Confirm which lines connected to valve "C" go to the service tank and which go toward the pilot passages feeding distributor valve "A". • Verify whether the diagram shows valve "C" controlling port-side or starboard-side flow when the port unit is started. • Eliminate any options that would continuously send replenishing flow to the service tank, since that would prevent building the pilot pressure needed to shift distributor valve "A".