The high-pressure bleed-air system uses bleed air from the engine high-pressure bleed-air port to supply the wing anti-ice system. The high-pressure bleed-air system is divided into left and right sides. System pressure is controlled by regulating valves that also allow the system to shut off.

The high-pressure ducts and pipes of the high-pressure bleed-air system are made from stainless steel and titanium. They are installed with some supports that move and with a minimum of hard mounts. Hard mounting is done by tie rods or directly to structural brackets. Flexible joints are installed along the ducts to be resistant to manufacturing and installation tolerances, structural movement, and thermal expansion of the ducts.

High pressure ducts have insulation that prevent the temperature to be more than 200 °C (392 °F). Small holes are found on the insulation shell. Air leakage from the ducts is collected in the shell and removed through the holes that supply air on the leak detection loops. Insulated ducts with flanges are attached one to the other with Inconel couplings which have coupling covers made from silicone rubber.

The high pressure valve (HPV) is installed in the aft equipment compartment, near the pylon interface. It is a spring-loaded closed, electrically controlled, pneumatic valve. The HPV controls the bleed air from the high-pressure engine port.

The HPV has a butterfly valve made from a 2 in (5.08 cm) diameter valve body and butterfly plate on an inclined axis. The valve body and butterfly plate are made of stainless steel. The valve body has an upstream pressure tapping to supply the pressure reducer with pressurized air. The butterfly plate position is indicated by an arrow on the lever attached to the butterfly shaft. The arrow points to the words OPEN and CLOSED that are written on the valve body. The HPV has a lever that can be manually set and locked in the full closed position with the vent screw. It has a pressure reducer and regulator which controls the pressure in the pneumatic actuator. There is a pneumatic actuator made of a diaphragm, a cylinder assembly, and a spring which closes the butterfly plate.

The HPV has a solenoid valve installed downstream of the pressure reducer. The solenoid valve is a valve that is spring-loaded to the open position. The HPV has an end of the travel microswitch operated by the butterfly valve. The microswitch supplies the signals (FULL CLOSED and NOT FULL CLOSED) to the engine indication and crew alerting system (EICAS) to show the valve position display on the ANTI-ICE synoptic page.

The pressure adjustment is fully pneumatic. Without upstream pressure, the HPV is closed. With upstream pressure of a minimum of 10 psig (68.95 kPa) and no 28 VDC voltage applied to the solenoid valve, the HPV is closed. With the upstream pressure and voltage applied to the solenoid valve, the HPV is open and controls the air flow to a maximum of 36 ± 3 psig (248.21 ± 20.68 kPa).

Upstream air pressure is supplied to the pressure reducer which then pressurizes the pressure regulator. The pressure regulator supplies the pneumatic actuator. Downstream air pressure is measured by a pressure tapping downstream of the HPV and connected to the pressure regulator. The downstream pressure measurement is used to control the position of the pressure regulator clapper, which controls the pressure in the valve actuation chamber.

When the downstream pressure increase above 36 psig (248.21 kPa), the butterfly plate moves to the closed position. When the pressure upstream of the HPV falls under 36 psig (248.21 kPa), the butterfly plate moves to the full open position. The HPV is moved to the closed position when the system is off, when the related engine is off.

The related HPV also closes when the ENG FIRE pushbutton annunciator (PBA) on the ENGINE control panel on the same side is pushed. The XBLEED switch on the ANTI-ICE control panel can also close the HPV. With the XBLEED switch in the FROM L position, the right HPV will close. With the XBLEED switch in the FROM R position, the left HPV will close.

The high-pressure sensors are found in the aft equipment compartment, downstream of the HPVs. The sensor is an absolute pressure transducer that can measure pressure from 0 to 75 psig (0 to 517.11 kPa). It monitors the HPV output pressure.

The high-pressure port duct is found in the aft equipment compartment at the pylon firewall. It connects the engine high-pressure port to the HPV.

The high-pressure bleed pipe is found in the aft equipment compartment. It connects the HPV to the WAIV.

The engine-nacelle HP bleed-duct is found in the engine nacelle. It connects the engine high-pressure port of the engine to the high-pressure port duct.

High pressure air from the engine high-pressure port is supplied to the high-pressure bleed-air system. The air goes through the engine-nacelle HP bleed-duct and through the high-pressure port duct at the pylon firewall. This air goes to the HPV, where the air pressure is adjusted at 36 ±3 psig (248.21 ± 20.68 kPa). The air then goes through the high-pressure bleed pipe to the wing anti-ice system. The flight crew can close the HPVs with the selection of the wing anti-ice system switches on the anti-ice control panel.

Two integrated air system (IAS) controllers monitor the high-pressure bleed-air system. The IAS controllers use the high pressure sensors to monitor system pressure. The IAS controllers also use the microswitches on the HPVs to monitor valve position. The controllers then show this data on the EICAS ANTI-ICE synoptic page. Also, different malfunctions will give EICAS messages.

The L (R) PYLON BLEED LEAK warning message will show when a leak is sensed at the left (right) HPV inlet. The WING ANTI-ICE LEAK warning message will show when a leak is sensed at the left (right) HPV outlet.

The L (R) WING A/I PRESS HI caution message will show when an overpressure is sensed downstream the left (right) HPV. The L (R) WING ANTI-ICE FAIL caution message will show when the left (right) HPV regulates too low or it is failed in the closed position.

The WING ANTI-ICE FAULT advisory message will show when the left (right) high pressure sensor is out of range.

The EICAS messages that follow are related to the high-pressure bleed-air system:

The high-pressure bleed air system interfaces with the following systems/components:

• Integrated air system (IAS) controller
• Anti-ice system
• Wing anti-ice system
• Bleed-air leak detection system
• ENGINE Control Panel

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The IAS controllers do a continuous built-in-test (CBIT) which include the test of some components of the high-pressure bleed-air system. The IAS controllers continuously monitor the pressure read by the high pressure sensor. They monitor the HPV in the case it fails open or fails closed.