HYDRAULIC GROUND SERVICING FILTER - REMOVAL/INSTALLATION
1. General
A. A container will be necessary to catch fluid from the disconnected hydraulic lines. Should any fluid spill on the airplane, decontaminate. Refer to Chapter 12, Cleaning and Washing.
2. Equipment and Materials
A. Skydrol Assembly Lube - MCS 352 or Fire-Resistant Hydraulic Fluid, BMS\3-11.
3. Remove Hydraulic Ground Servicing Filter
A. Gain access to filter located in the right wheel well.
B. Disconnect lines from inlet and outlet ports of filter (Fig. 401).
C. Cap open lines and plug filter ports to prevent contamination.
D. Remove mounting bolts and remove filter.
4. Install Hydraulic Ground Servicing Filter
A. Install 0-ring and union in each port (Fig. 401). Lubricate with assembly lube or hydraulic fluid.
B. Place filter in mounting position and install mounting bolts.
C. Connect hydraulic lines to inlet and outlet ports.
D. Check the filter bowl is tight and lockwired.
E. Connect ground servicing source and check filter and connections for leaks.
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Feb 15/73 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 29-09-221 Page 401
F86101
Hydraulic Ground Servicing Filter Installation 501
29-09-221 Figure 401 Feb 01/76
Page 402
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
HYDRAULIC RESERVOIR PRESSURIZATION SYSTEM - DESCRIPTION AND OPERATION
1. General (Fig. 1)
A. The reservoir pressurization system supplies bleed air from No. 1 and 2 engines to pressurize system A, system B, and standby hydraulic reservoirs. The system provides a positive supply of hydraulic fluid to the pumps and prevents foaming in the reservoirs. A constant pressure of 40 to 47 psi is maintained in the reservoirs by a pressure regulator which also operates as a vacuum relief valve to relieve negative pressures in the reservoirs. Overpressurization of the system is prevented by a system relief valve set to relieve between 60 and 65 psi. The pressurization system also contains an air pressure filter, vent filter, check valves, restrictors, ground air charging (test) valve, relief valve, air manifold, reservoir air bleed valve and sump tube and drain fitting or vented cap.
2. Ground Air Charging (Test) Valve (Fig. 1)
A. The ground air charging (test) valve is provided to attach an external air source to the reservoir pressurization system. An external air source should be used during ground test procedures to provide a positive fluid flow and to increase the hydraulic return systems to normal operating pressures. The valve is installed on the air manifold located on the upper surface of the right wheel well area.
3. Air Pressure Regulator (Fig. 1)
A. The air pressure regulator maintains a constant pressure of 40 to 47 psi in the hydraulic reservoirs. The regulator operates as a vacuum relief valve and a pressure relief valve. The regulator consists of the pressure valve, poppet valve, spring and diaphragm. On some airplanes, a check valve is installed in the IN (inlet) port of the regulator to maintain system pressure. The regulator is installed on the upper surface of the wheel well area. Ambient pressure and spring forces acting on the diaphragm control the regulator. Air from engines No. 1 and 2 flows to the regulator. When the reservoir is below regulated pressure, air will flow through the poppet valve to the reservoir until the regulated pressure is obtained. As pressure in the reservoir overcomes spring and ambient pressure the poppet closes, preventing air from entering. As air pressure in the reservoir rises over regulated pressure, air pressure inside the reservoir overcomes spring and ambient pressure opening the pressure valve allowing air to escape until regulated pressure is obtained. As pressure in the reservoirs drops 0.50 psi under ambient pressure, the ambient valve opens allowing ambient air to enter the reservoir, preventing vacuum in the reservoir. An air pressure gauge is installed at the outlet of the air pressure regulator.
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