-
ENG BLEED pushbutton switch.
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Bleed Pressure Regulator Valve (PRV)
Figure 020
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Bleed Pressure Regulator Valve (PRV)
Figure 020A
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Bleed Pressure Regulator Valve (PRV)
Figure 020B
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The PRV closes pneumatically in case of impending reverse flow to the engine. The Overpressure Valve (OPV) installed downstream of the PRV protects the system against damage if overpressure occurs. A sense line (1/4 in. dia.) connects the PRV to the HP Bleed Valve in order to close the HP Bleed Valve if the PRV is closed or controlled to close. The thermal fuse installed in the valve body causes the valve to close at 450 plus or minus 25 deg.C.
C. Not Applicable
R **ON A/C 151-199, 401-499,
B. Solenoid HP Bleed Override
(Ref. Fig. 021)
(1)
Although allowing the air bleed on the IP port of the engine, the solenoid when energized permits to control closure of the HP Bleed Valve.
(2)
Operation The unit comprises a solenoid actuated valve, with spring return. When the unit is de-energized, the valve seals the HPV to PRV sense line, the internal parts of the solenoid are at atmospheric pressure. Energizing the unit opens the valve allowing air to flow from the HPV to PRV sense line to atmosphere.
C. Bleed Pressure Regulator Valve (PRV)
(Ref. Fig. 020A)
(1) The PRV is a 4 in. dia. butterfly-type valve, normally spring-loaded closed in absence of upstream pressure. A minimum upstream pressure of 8 psig is necessary to open the valve. The PRV pneumatically regulates the downstream pressure to 44 plus or minus 3 psig. It closes automatically in the following cases : - overtemperature downstream of the precooler exchanger (257 plus or
minus 3) deg.C (60 s delay) - overpressure downstream of the PRV (57 plus or minus 3) psig (15 s delay)
-ambient overheat in pylon/wing/fuselage ducts surrounding areas
-APU bleed valve not closed
-corresponding starter valve not closed. It is controlled in closed position by crew action on:
-
ENG FIRE pushbutton switch
-
ENG BLEED pushbutton switch.
Solenoid HP Bleed Override
Figure 021
R 1EFF : 151-199, 401-499, 1 36-11-00Page 75 1 1 Aug 01/05 1 1 1CES 1 The PRV closes pneumatically in case of impending reverse flow to the engine. The Overpressure Valve (OPV) installed downstream of the PRV protects the system against damage if overpressure occurs. A sense line (1/4 in. dia.) connects the PRV to the HP Bleed Valve in order to close the HP Bleed Valve if the PRV is closed or controlled to close. The thermal fuse installed in the valve body causes the valve to close at 450 plus or minus 25 deg.C.
**ON A/C ALL
(2) Detailed Description
**ON A/C 001-003, 051-054, 056-056,
(Ref. Fig. 022)
R **ON A/C 004-049, 055-055, 057-099, 101-149, 151-199, 201-299, 301-399, R 401-499,
(Ref. Fig. 022A)
**ON A/C ALL
The PRV contains three main parts :
-
a valve body,
-
a pneumatic actuator,
-
a regulator assembly.
(a) Regulation The upstream pressure supplies chamber (1) of the regulator through a jet to control the position of the clapper (2) and maintain constant air pressure in the actuator opening chamber. The regulator calibration can be modified by the secondary stage of the regulator which is pneumatically connected to the Bleed Pressure regulator valve Control Soleno]d according to the air temperature sensed downstream to the PCE. The air pressure in chamber (3) can vary according to an air leakage controlled by the Bleed Pressure Regulator Valve Control Soleno]d. As clapper
(2) remains in contact with its seat (4), downstream pressure still supplies the actuator closing chamber despite a reduced pressure air value lower than the nominal regulation threshold. The test intake is used for checking correct valve operation on the ground by directly supplying the regulator.
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Bleed Pressure Regulator Valve (PRV) - Schematic
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