Pressure limitation system (Ref. Fig. Engine Bleed Air - Pressure Limitation System )
This sub-system includes a bleed pressure regulating valve designated bleed valve associated with a bleed valve control solenoid. This sub-system enables the aircraft systems to be supplied with air under a normal nominal pressure lower than or equal to 48 psig (cruise normal flow). The IP stage bleed air pressure (or HP stage pressure if the HP bleed valve fails in the open position) is limited downstream of the bleed valve.
The bleed valve operates pneumatically in relation with the associated bleed valve control solenoid. The bleed valve control solenoid is connected to the bleed valve by a pneumatic sense line and is installed in the duct downstream of the precooler exchanger. The bleed valve control solenoid controls the bleed valve closure when the valve solenoid is energized by the BMC or by action on the ENG BLEED pushbutton switch or ENG FIRE. The bleed valve control solenoid reduces the bleed valve regulated pressure when the temperature exceeds 235°C. In case of overpressure caused by the bleed valve failure, the overpressure valve closes.