737 AMM 飞机维护手册 液压 HYDRAULIC POWER(5)

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3.  Hydraulic Fluid
A.  BMS 3-11 is the general specification for the fluid that is circulated through all hydraulically operated systems. It is a fire-resistant base fluid to which suitable additives have been incorporated. All types of fluid under this specification are completely miscible with each other in any degree of mixture with no separation, precipitation or cloudiness. All airplane equipment using BMS 3-11 are identified by nameplates. Areas where hydraulic fluid may leak are designated as possible BMS 3-11 contamination areas. Special paint and protective finishes are used to prevent damage in these areas. Refer to Chapter 51, Structures - Protective Finishes.
B.  BMS 3-11 has little or no effect on the metals used in aircraft construction up to 240°F. Only materials compatible with BMS 3-11 fluids, such as ethylene propylene, butyl rubber and teflon, are used for system seals, gaskets, O-rings, and hose linings.
C.  Skin irritation in the form of dry or cracked skin may result from prolonged or repeated contact with BMS 3-11. It also causes painful but temporary irritation to the eyes and may produce a burning sensation to other sensitive parts of the body. Inhalation of the fluid in the form of spray of fine mist may cause irritation of the upper respiratory tract. To minimize contact with BMS 3-11, wear gloves, goggles, face shields or safety glasses whenever there is danger of exposure. If exposure occurs, flush the eyes immediately with water and report to medical for observation.
501 
May 15/70  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  29-00 Page 3 

F85890
Hydraulic Ground Power Modular Unit  500 
29-00  Figure 2  May 15/67 
Page 4 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

4.  Hydraulic Tubing and Flexible Hoses
A.  Hydraulic Tubing
(1)  The hydraulic pressure lines in the airplane hydraulic systems subject to pressures of 1500 psi and above are made of corrosion resistant seamless steel tubing. It also is used in class I fire zones and on the landing gear structure regardless of pressure. All other lines are made of aluminum alloy seamless tubing. Tubing of 3/4-inch outside diameter and under uses flareless type fittings. For pressures of 1500 psi and above steel fittings are used. Tubing above 3/4-inch outside diameter uses flared type fittings. On this tubing size, aluminum fittings are used, except in class I fire zones and on the landing gear structure where steel fittings are used. For further information, refer to 20-10-51, Flareless Tubing, 20-10-52, Flexible Hose and 20-50-11, Standard Torque Values.
B.  Flexible Hoses
(1)  Flexible hose used in the hydraulic systems are teflon high and medium pressure type. High pressure hoses are used in the pressure lines. Medium pressure hoses are used in supply lines and return lines.
5.  Hydraulic System Check Valves
A.  Check valves are installed in the hydraulic power systems to prevent -ERROR- flow of fluid, direct fluid flow, prevent fluid loss, and to isolate hydraulically operated subsystems. Flow direction through a valve is shown by an arrow on the valve body. Normally no maintenance other than removal and installation is required of a check valve.
6.  Hydraulic Ground Power Modular Unit
A.  The hydraulic ground power modular unit (Fig. 2) is located on the forward side of the forward bulkhead of the right wheel well and is accessible through an access panel on the right side of the airplane. The modular unit is used to connect an external hydraulic power source to pressurize systems A and B. The module consists of a pressure connection, return connection, and a filter containing a noncleanable element.
523 
Nov 01/74  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  29-00 Page 5 

HYDRAULIC POWER - MAINTENANCE PRACTICES
1.  General
A.  The following procedure is used to change the fluid in the hydraulic system. If severe contamination is present in the system and flushing is required before refilling, refer to the Maintenance Practices section of the applicable subsystem.
B.  Whenever hydraulic system components are disassembled, cleaned, overhauled or installed, flushing with BMS 3-11 hydraulic fluid only is recommended to avoid fluid contamination within the operational system by incompatible materials.
WARNING:  FIRE-RESISTANT HYDRAULIC FLUIDS CONFORMING TO BMS 3-11 MAY CAUSE SKIN IRRITATION. AVOID PROLONGED OR REPEATED CONTACT WITH SKIN. IN CASE OF EYE CONTACT, FLUSH EYES WITH WATER AND OBTAIN MEDICAL AID. IN CASE OF INGESTION, OBTAIN MEDICAL AID.
C.  To change the hydraulic fluid in the system, a ground test bench or the system B pumps can be used to introduce the new fluid and purge the system. To ensure satisfactory performance, the new fluid should be checked after thorough mixing has taken place by operating all systems, preferably after flight (Ref 29-09-111, Inspection/Check).
　
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