F61944
System B Hydraulic Reservoir Low Level Warning Switch Installation 500
29-33-31 Figure 401 Feb 01/96
Page 402
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
HYDRAULIC PUMP LOW PRESSURE WARNING SYSTEMS - DESCRIPTION AND OPERATION
1. General
A. The hydraulic pump low pressure warning systems give an amber light warning signal when pump delivery pressure is low (Fig. 1). Five independent hydraulic pump low pressure warning systems are installed, one for each engine-driven hydraulic pump, one for each system B electric motor-driven pump and one for the standby pump. Each warning system consists of an amber low pressure light on the pilots' overhead panel, and a cartridge type low pressure warning switch installed in the associated modular unit pump discharge line. The system A engine-driven hydraulic pump warning systems are wired through their appropriate engine fire switch. Positioning an engine fire switch to FIRE will de-energize the warning system. Each system warning light illuminates when electric power is on and the pump delivery pressure drops below the preset pressure of the low pressure warning switch. Each warning system is powered by 28 volts.
NOTE: Pump low pressure warning lights indicate pump pressurization and do not reflect system hydraulic pressure. If an engine driven pump is depressurized when the opposite pump is pressurized, pressure between the downstream check valve and the blocking valve of the depressurized pump must bleed back through the blocking valve. This will increase the delay in illumination of the low pressure light.
506
Jun 20/86 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 29-34-0 Page 1
F87972
Hydraulic Pump Low Pressure Warning System Schematic 500
29-34-0 Figure 1 Feb 15/69
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
HYDRAULIC PUMP LOW PRESSURE WARNING SYSTEM - ADJUSTMENT/TEST
1. General
A. The low pressure warning system is tested for electrical continuity between the low pressure warning lights and pressure switches and for proper operation and pressure settings of the switches. Pressure settings are checked by applying controlled pressure to each individual low pressure switch. The settings of the switches are manufacturer adjusted and there is no adjustment to be done.
B. A container will be necessary to catch any fluid leakage from disconnected hydraulic lines. Should any fluid spill on the airplane, decontaminate. Refer to Chapter 12, Cleaning and Washing.
2. Hydraulic Pump Low Pressure Warning System Test
A. Equipment and Materials
(1) Hydraulic ground test bench, 0 to 3000 psi
B. Prepare to Test Low Pressure Warning System
(1)
Provide electrical power to airplane.
(2)
Check that the following circuit breakers on the P6 panel are closed:
(a)
Indicator Light circuit breakers
(b)
Dim and Test Control circuit breakers
(c)
Sect. 1, Sect. 4, Sect. 5, and Sect. 6 circuit breakers
C. Test Low Pressure Warning System
(1) Test system A low pressure warning system.
(a)
Reset master caution light.
(b)
Disconnect pressure hose from Engine No. 1 hydraulic pump and connect hose to ground test bench. Cap pressure port of pump.
(c)
Check that system A low pressure warning lights are illuminated.
(d)
Operate the ground test bench and slowly increase hydraulic pressure:
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