RESERVOIR AIR PRESSURIZATIONAll thr

RESERVOIR AIR PRESSURIZATIONAll three reservoirs are pressurized to 50 psi to prevent pumpcavitation.The non-return valves are in each reservoir supply manifold. Makesure that the pressure is kept for until 12 hours after engine shutdownon ground and for until 3 hours after a failure of the air supply inflight.Each reservoir has a depressurization valve on its related service panel.For long time depressurization, a depressurization tool can be installedon the depressurization valve.A 77 psi pressure relief valve is installed onto the supply manifold ateach reservoir.All three reservoirs are pressurized directly from Engine 1 for normalsupply and from the bleed air system for alternate supply at 43 psi.The air pressurization manifold has a ground supply connection.It is put into the blue hydraulic bay and adjusts the normal or groundsupply to 50 psi.There are two water drains: one is automatic after engine and APUshutdown, and the other is manually operated.After maintenance on the hydraulic system, the reservoir pressurizationcan be done with a pneumatic ground cart connected to the reservoirpressure unit, the APU or the pneumatic system ground connection.