Removal/Installation 401 ALL
TRANSMITTER - DUCT PRESSURE 36-21-11 Servicing 301 ALL Removal/Installation 401 ALL
36-CONTENTS
BEJ Page 4 Nov 15/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
PNEUMATIC SYSTEM - DESCRIPTION AND OPERATION
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1. General_______
A. The purpose of the pneumatic system is to supply bleed air from the 5th and 9th stage of the engine compressor or from the APU or from a ground cart. Air is distributed by a pneumatic manifold from the above sources to the air conditioning packs, wing and cowl Thermal Anti-Ice (TAI) systems, the engine starting system, potable water system and the hydraulic reservoir. The systems using air from the pneumatic manifold are covered in their respective chapters.
B. The main supply of bleed air to the manifold is obtained from the engine 5th stage compressor. 5th stage air is supplied to the pneumatic manifold at all times except at engine idle or at low engine thrust settings. When this occurs 9th stage bleed air is automatically used. Air from the 5th and 9th stage bleed ports is controlled by the engine bleed control system described in Chapter 36-11-05. APU bleed air or pneumatic ground cart bleed air is primarily used for engine starting and for air conditioning pack operation on the ground. The APU can be used as an alternate bleed air source up to airplane altitudes of 17,000 ft.
C. The pneumatic manifold interconnects the engine bleed system and APU and distributes bleed air to the systems outlined in paragraph A. The pneumatic manifold contains the necessary valves to shut off bleed air at each engine, APU and to isolate the left and right hand systems.
D. Each engine bleed system contains a bleed air temperature control sub-system. This consists of a precooler, precooler control valve and precooler control valve sensor. The engine bleed air temperature is automatically controlled to a preset temperature whenever the engine is operating and the Pressure Regulator and Shutoff Valve (PRSOV) is open. The temperature is sensed in the precooler bleed air discharge. The sensor will cause the precooler control valve to modulate open/closed as required to maintain this temperature. Engine fan air is used as the heat sink for the bleed air.
E. Two pressure transmitters are provided for pressure indication of the bleed air. One transmitter is used for each engine. Both pressure transmitters are connected to a dual pressure indicator on the overhead panel. The engine bleed air overtemperature indication consists of overtemperature switches in the ducting system, which are connected to the overhead panel trip lights. The temperature switches illuminate the trip lights and the corresponding engine PRSOV closes when the bleed air temperature exceeds approximately 490°F. Also, the bleed trip light will illuminate if there is excessive pressure at the bleed valve inlet.
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36-05-00
ALL ú ú 01 Page 1 ú Jul 15/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
F. The high-stage manifold duct on the engine has a bleed air pressure tap provision to supply pneumatic pressure to airplanes equipped with potable water engine pressurization system.
(1)
AIRPLANES WITH POTABLE WATER ENGINE PRESSURIZATION SYSTEM; Make sure that the potable water pressure line is connected to the pressure tap on engine 1 (AMM 71-00-02/401).
(2)
AIRPLANES WITHOUT POTABLE WATER ENGINE PRESSURIZATION SYSTEM; Make sure that the pressure tap provision on the replacement engines are sealed (AMM 71-00-02/401).
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