B767 ATA 47 Student Book

TRAINING MANUALFOR TRAINING PURPOSES ONLY

B767-3S2F ATA 47-00 Page - 1 4/24/13 EFF - ALL

NGS CH 47



TABLE OF CONTENTS

GENERAL DESCRIPTION............................................................................... 4

GENERAL DESCRIPTION (CONT)................................................................. 6

THERMAL CONTROL UNIT..............................................................................8

SHUTOFF VALVE............................................................................................10

OZOZNE CONVERTER AND PRESSURE SENSOR..................................... 12

RAM AIR FAN AND PRIMARY HEAT EXCHANGER...................................... 14

TEMPERATURE CONTROL VALVE...............................................................16

TURBOCOMPRESSOR AND TURBOCOMPRESSOR SHUTOFF VALVE....18

REGEN HEAT EXCHANGER..........................................................................20

COMPRESSOR OUTLET TEMPERATURE SENSOR AND THERMAL

SWITCH...........................................................................................................22

AIR FILTER AND DIFFERENTIAL PRESSURE SWITCH............................... 24

AIR SEPERATION UNIT................................................................................ 26

OVERTEMPERATURE SHUTOFF VALVE,THERMAL SWITCH AND INLET

TEMPERATURE SENSOR............................................................................. 28

OVERTEMPERATURE SHUTOFF VALVE......................................................30

AIRSEPERATION MODULE............................................................................ 32

HIGH FLOW VALVE AND OXYGEN SENSOR............................................... 34

DIFFERENTIAL PRESSURE SENSOR AND FLOW ORIFICES...................... 36

DISTRIBUTION SYSYTEM GENERAL DESCRIPTION..................................38

DISTRIBUTION SYSTEM COMPONENTS.....................................................40

NITROGEN GENERATIONSYSTEM CONTROLLER.................................... 42

BITE DISPLAY UNIT........................................................................................44

BITE DISPLAY FUNCTIONS............................................................................46

INDICATIONS.................................................................................................. 48



STUDENT NOTES:



NGS - GENERAL DESCRIPTION

General

The Nitrogen Generation System (NGS) makes Nitrogen Enriched Air (NEA). The NEA goes to the center fuel tank through the Nitrogen Enriched Air Distribution System (NEADS). The NGS makes NEA at a rate enough to reduce the oxygen concentration in the center fuel tank below that required to sustain combustion. The NGS is in the wing to body fairing. The NGS gets bleed air from the aircraft pneumatic system crossover manifold. The NGS gets cooling air from the NGS ram air inlet. The NGS thermal control system conditions the bleed air, and the NGS air separation system separates the bleed air into two compounds:

• NEA • Oxygen Enriched Air (OEA)

OEA is a waste gas that is dumped overboard through a dedicated exhaust line.The NGS gives the following functions:

• Sends NEA to the center fuel tank in order to reduce the risk of fire in the fuel tank

• Supply the required amount of NEA with regulated temperature to the fuel tank, for different flight profiles

• Shut off the air supply flow when the NGS supply temperature gets to the temperature control limits

• Show the NGS parameters for information and maintenance purposes • Give fault reporting and BIT related information through the BITE display

unit (BDU)

The NGS has these major subsystems:

• Thermal Control System • Air Separation Unit (ASU) • Nitrogen Enriched Air Distribution System (NEADS) • Control System

Thermal Control Unit

The NGS Shutoff Valve (SOV) gets bleed air from the left side of the pneumatic manifold. The NGS SOV controls the flow of air to the NGS. The NGS

controller (NGSC) controls the NGS SOV with inputs from the system interface and airplane systems.

The air goes through the primary heat exchanger and is cooled by the NGS ram air. The NGSC monitors the temperature sensor and modulates the temperature control valve (TCV). The TCV modulates to keep the primary heat exchanger output air temperature within the correct operating limits.

During descent and ground operations, the NGS operates in the boosted mode. The TCSOV opens and lets bleed air go to the turbo compressor (TC). Air that goes through the turbine side of the turbo compressor gets cooled through expansion. This air then precools the air entering the compressor section of the TC. The boosted air then goes to the primary heat exchanger and TCV.

Air Separation Unit

Air from the TCU goes into the ASU at a regulated temperature of 170F (77C) through the Over Temperature Shutoff Valve (OTSOV).

There are three Air Separation Modules (ASM) in the ASU. The ASMs separate the oxygen molecules from the nitrogen molecules in the air supply. This function leaves NEA that goes to the NEADS. NEADS sends this NEA to the center fuel tank. The NEA does not have enough oxygen to support an ignition of the fuel/air mixture. The oxygen in the air goes to a level that is too low tosupport combustion. The Oxygen Enriched Air (OEA) is vented overboard.

The NGS operates in both a high and a low flow mode. The NGSC uses the airplane flight configuration to control for low and high flow modes. When the NGS operates in the low flow mode the NGSC closes the High Flow Valve(HFV). NEA goes through the low flow orifice. When the NGSC opens the HFV, the NEA can go through both the low flow orifice, and the high flow orifice. The NGSC uses a differential pressure sensor to monitor when the NGS operates in the low flow or high flow modes. The NGSC uses this information for possible system fault detection.

The NGSC uses an oxygen sensor to test the NEA for the amount of oxygen that remains in the NEA. The NGSC uses the oxygen sensor to monitor for NGS performance degradation.



NGS - GENERAL DESCRIPTION



NGS - GENERAL DESCRIPTION (CONT)

Distribution System

The NEADS sends the NEA to the center fuel tank. The distribution section has these parts:

• Tubes • Check valves • Float valve • Vent channel • Drain

Built-In Test

The NGSC has Built-In Test (BIT) capability. Faults found with BIT are stored in the controllers nonvolatile memory. The NGSC also monitors and records theperformance of the NGS.

The controller sends fault information to the BITE Display Unit (BDU).

When the NGS is operating in a degraded mode, an Engine Instrument Crew Alerting System (EICAS) message shows.

The BDU is used for fault monitoring, system test, and system configuration data.

A status indicator panel gives a fast way to show the status of the NGS for airplane dispatch purposes.



NGS - GENERAL DESCRIPTION (CONT)



NITROGEN GENERATION SYSTEM - THERMAL CONTROL UNIT - GENERAL DESCRIPTION

General Description

The Nitrogen Generation System (NGS) uses hot bleed air to make Nitrogen Enriched Air (NEA) for the center fuel tank. The Thermal Control Unit (TCU) controls the bleed air pressure and temperature and delivers the air tothe Air Separation Unit (ASU).

These components are on a frame assembly along with associated tubes and ducting. The assembly is mounted to the aircraft forward of the left ECS bay.These are the components of the Thermal Control Unit (TCU):

• Ozone converter • Turbocompressor shutoff valve (TCSOV) • Turbocompressor (TC) • Regen heat exchanger • Temperature sensor • Compressor overtemperature thermal switch (COTS) • Pressure sensor • Check valve • Temperature control valve (TCV) • Primary heat exchanger • Filter • Differential pressure switch • Fan • Ram air check valve • Ram air exit

The NGS Shutoff Valve (SOV), filter and differential pressure sensor are not part of the TCU frame assembly. The NGS SOV valve opens to let bleed air into the TCU. The NGS SOV also controls the bleed air pressure to the TCU.

The ozone converter uses a catalytic process to convert ozone molecules to oxygen molecules. This helps to prevent oxidation of the components inside the three Air Separation Modules (ASM). The ASMs are in the ASU.

The TCSOV controls bleed air flow to the turbine section of the TC. With the TCSOV open, the TC is on. The NGSC uses the TC for boosted operation of the NGS.

The regen heat exchanger cools the air that goes to the compressor section of the TC.

The NGSC monitors the TC compressor outlet temperature with the temperature sensor. The NGSC will close the TCSOV if TC compressor outlet temperature becomes too high.

The COTS does a back up to the NGS Controller (NGSC) to close the TCSOV. The COTS can close the TCSOV if TC compressor outlet temperature becomes too high.

The NGSC monitors the bleed air pressure in the ASU with the pressure sensor. The NGSC uses the pressure information for fault monitoring, BITE, andoverpressure protection.

The TC check valve prevents a reverse flow of air out of the TC compressor back through the ozone converter and pneumatic system. The check valve prevents this reverse flow with the TC on in the NGS high boost mode.

The NGSC uses the temperature control valve (TCV) to control how much air goes through the primary heat exchanger. The NGSC uses the TCV and primary heat exchanger to control the temperature of the air that goes from the TCU to the ASU.

The primary heat exchanger uses cooler ram air to cool the air supply that goes from the TCU to the ASU.

The filter removes contaminants and excess water from the TCU air supply that goes to the ASU. The filter protects the ASMs and other components in the ASU from contamination damage.

The NGSC uses the differential pressure switch to monitor the condition of the filter. The NGSC uses the pressure switch information to show the status of theNGS, and for fault information. The NGSC uses the ground fan to help move air through the ram air duct. The NGSC turns on the ground fan when the NGS operates with the airplane on the ground. The ram air duct gives cooling air to the primary heat exchanger. The ram air check valve prevents air flow from theground fan from recirculating back through the ground fan. The check valve closes with the ground fan on.



NITROGEN GENERATION SYSTEM - THERMAL CONTROL UNIT - GENERAL DESCRIPTION



NGS - SHUTOFF VALVE

General

The Nitrogen Generation System (NGS) Shutoff Valve (SOV) is in the bleed air duct that goes to the Thermal Control Unit (TCU). The valve controls airplane bleed air flow to the NGS through the TCU.

The NGS SOV regulates the bleed air pressure into the TCU and NGS at 52 +/- 6 psig.

The SOV is an electrically controlled, pneumatically operated Pressure Regulating and Shutoff Valve (PRSOV). The butterfly spring loads to the closed position. The valve has a visual position indicator that you can move and lock in the closed position.

Normal Operation

During normal operation, a constant reference pressure goes to the base of the solenoid and the shuttle valve. When the solenoid energizes, the solenoid ball valve moves off of its seat to seal the ambient vent. Reference pressure goes to the opening chamber of the actuator. In the shuttle valve, with the referencepressure more than downstream pressure, the shuttle element holds in the position shown. Reference pressure goes to the closing chamber of the actuator. Because the opening chamber area is larger than the closing chamber area, the valve moves to full open position.

As the butterfly opens, the downstream pressure increases. When the downstream pressure is more than the reference pressure, the shuttle element moves to the position opposite of the position shown. Downstream pressure goes to the closing chamber of the actuator. For normal system operation, the downstream pressure is less than the regulation set point of the valve.

Pressure Regulating Function

When downstream pressure increases to the regulation set point of the valve, downstream pressure in the closing chamber and the force of the spring add together. This balances the force from the reference pressure in the opening chamber. The butterfly moves as necessary to keep the balance and to control the downstream pressure.

Shutdown

When the solenoid de-energizes, the ball valve closes. This removes reference pressure to the opening chamber of the actuator. The opening chamber has an opening to ambient through the solenoid vent. The spring keeps the butterfly valve in the closed position. Reference pressure goes through the shuttle valve to the closing chamber. This helps the spring close the valve.



NGS - SHUTOFF VALVE



NGS - OZONE CONVERTER AND PRESSURE SENSOR

Ozone Converter Purpose

The ozone converter decreases the ozone content in the bleed air. The converter converts the ozone to oxygen. This helps to protect the permeable fiber membrane material inside the three Air Separation Modules (ASM)from oxidation. The ASMs are in the Air Separation Unit (ASU).

Physical Description

The ozone converter is in the Thermal Control Unit (TCU).

The ozone converter is an aluminum, plate fin, single pass, cross-flow to air unit. It has an inlet and an outlet at each end. The approximate dimensions are, length 8.3 inches (21 cm), diameter is 3.9 inches (7.6 cm). The weight is 3.5 lb (1.5 kg).

Operation

The ozone converter removes the ozone from the air by a catalytic process. The process converts the ozone to oxygen. Hot bleed air enters the catalytic converter. The bleed air contacts the catalytic reactor core and converts to oxygen. The bleed air then goes out of the catalytic converter.

Bleed Pressure Sensor Purpose

The NGS controller (NGSC) uses a pressure sensor to monitor the air inlet pressure to the NGS. The NGSC uses the pressure information for these functions:

• BITE • Fault indication • Overpressure protection

LocationThe pressure sensor is in the Thermal Control Unit (TCU), inboard and aft of the ozone converter.

Functional Description

The sensor has pressure sensitive elements hermetically sealed in a shell. Pressure for the sensor comes from a sense line that connects to the TCU duct. The electrical connector on the sensor connects to the NGSC. The NGSC gives electrical excitation power to the sensor. The sensor sends electrical signals proportional to a sensed pressure to the NGSC. The pressure sensor is a gauge pressure sensor. The sensor gives an electrical signal proportional to an increase in pressure at the pressure port. The output range is 4 mA at 0 psig up to 20 mA at 100 psig.

The NGSC monitors the pressure sensor during NGS operation. An overpressure fault occurs when the NGSC senses bleed pressure more than 85 psig for more than 3 seconds.

With an overpressure fault the NGSC commands the NGS Shutoff Valve (SOV) and the Overtemperature Shutoff Valve (OTSOV) to close. The OTSOV is in the Air Separation Unit (ASU).

If the NGS operates in the boosted mode the NGSC will also command the Turbocompressor Shutoff Valve (TCSOV) to close.

These closed valves prevent an overpressure condition in the Air Separation Modules (ASM) and the center fuel tank. THE ASMs are in the ASU.



NGS - OZONE CONVERTER AND PRESSURE SENSOR



NGS - RAM AIR FAN AND PRIMARY HEAT EXCHANGER

Ram Air Fan Purpose

The Nitrogen Generation System (NGS) has a dedicated ram air system. A ram air fan increases cooling ram air flow to the primary heat exchanger with the airplane on the ground. The fan operates to add ram air cooling flow through the NGS heat exchanger during ground operation of the NGS.


The ram air fan is a motor-driven, single stage design. The fan operates with a three-phase, 115 vac motor. The ram air fan, or ground fan is in the ram air duct. The fan gives an airflow of 267 cubic feet per minute (CFM).

The ram air fan has internal limit switches. These switches open and remove electrical power from the motor. The switches open at 390F (200C).

Operation

Control for the fan comes from the Nitrogen Generation System Controller (NGSC). The NGSC uses a control circuit that connects to the fan relay. When the relay energizes, ac power goes to the fan motor. A ram air check valve prevents a reverse ram air flow when the ram air fan is on. When the airplane is in the air the ram air fan is off. Ram air goes through the ram air check valve to the primary heat exchanger.

Primary Heat Exchanger Purpose

The primary heat exchanger cools the engine bleed air before it enters the air separation unit (ASU) and goes through the air separation modules (ASM).


The heat exchanger is a single-pass aluminum, plate, cross-flow, air-to-air unit. It supplies a large surface area for efficient heat transfer from the bleedair to the air separation module (heat sink). The dimensions are, length 14.8 inches (37.5 cm), width 13.8 inches (35.5 cm), height 8 inches (20.4 cm). Theweight is 12.5 lb (5.7 kg).

General Description

The Nitrogen Generation System Controller (NGSC) uses the TCV to control how much air bypasses the heat exchanger.

As bleed air moves through the heat exchanger, it transfers heat to the walls of the heat exchanger. The walls are made of plates and fins. Ram air that goesthrough the heat exchanger on the other side of the walls removes the heat and carries it away. Heat transfer goes from the bleed air to the heat exchangerwalls, to the ram air. The heated ram air flow goes overboard.

Training Information Point

The heat exchanger uses narrow passages with thin walls and cooling fins for efficient heat exchange. Contamination or obstruction of the passages decreases or prevents airflow and heat transfer. Keep the heat exchanger clean for maximum performance.



NGS - RAM AIR FAN AND PRIMARY HEAT EXCHANGER



NGS - TEMPERATURE CONTROL VALVE

Purpose

The Temperature Control Valve (TCV) controls the temperature of the air flow to the Air Separation Modules (ASM). The ASMs are inside the Air SeparationUnit (ASU). The temperature is kept at an efficient operating level.

The TCV is in the TCU, at the inlet side of the primary heat exchanger.

General Description

The valve is an electrically controlled, pneumatically operated modulating valve. The valve is spring loaded to the closed position. The butterfly type valve ismodulated by the pneumatic actuator. The pneumatic actuator is controlled by the torque motor. The torque motor gets electrical commands from the nitrogengeneration system Nitrogen Generating System Controller (NGSC). The torque motor regulates the amount of air that opens the valve against spring pressure in the actuator.

The NGSC monitors the air temperature at the inlet of the Air Separation Modules (ASM). The NGSC uses the air separation module inlet temperature sensor to monitor the temperature. The ASMs and the sensor are in the airseparation unit (ASU).

The temperature control valve modulates to keep the air temperature to 160-180F (71-82C) at the inlet of the ASM. The valve controls the amount of air that bypasses the primary heat exchanger. Bleed air that does not bypass the primary heat exchanger, goes through the primary heat exchanger. This bleed air gets cooled by ram air that comes from ambient air. These are the parts of the valve:

• Electrical connector • Sensing lines • Reference pressure regulator • Actuator • Manual override and position indicator (not shown) • Manual lock mechanism (not shown) • Torque motor • Manual locking hex bolt (not shown)



NGS - TEMPERATURE CONTROL VALVE



NGS - TURBOCOMPRESSOR AND TURBOCOMPRESSOR SHUTOFF VALVE Purpose

The Nitrogen Generation System (NGS) Turbocompressor (TC) increases the NGS pressure during boosted operation.

Boosted operation occurs when the airplane pneumatic supply pressures are lower. The NGS controller (NGSC) controls the NGS for boosted and non-boosted operations.

Turbocompresor Operation

When the NGSC commands the Turbocompressor Shutoff Valve open (TCSOV), engine bleed air goes to the turbine inlet. The bleed air is drawn through the turbine by the lower absolute pressure at the turbine exit. The power produced by the turbine turns the compressor. Air in the turbine cools due to expansion from converting pressurized thermal energy to mechanical energy.

The air cooled by the turbine goes through the regen heat exchanger to cool the bleed air before it enters the compressor. Decreasing the bleed air temperaturebefore it enters the TC helps to limit the temperature of the compressor discharge air. Engine bleed air from the regen heat exchanger enters the compressor inlet, where the air goes to a higher pressure and temperature. The air from the compressor goes to the temperature control valve and primary heat exchanger. This function increases the airflow through the primary heat exchanger and bypass.

The Turbocompressor Check Valve (TCCV) operates when the TC operates. The TCCV prevents a reverse flow of compressor discharge air back through the ozone converter and the NGS shutoff valve (SOV). Cooling air to the TC bearing cavity comes from the bleed air exit side of the primary heat exchanger.

Turbocompressor Shutoff Valve Purpose

The Nitrogen Generation System Controller (NGSC) uses the Turbocompressor (TC) to operate the Nitrogen Generation System (NGS) in the boosted mode.

The NGS Turbocompressor Shutoff valve (TCSOV) controls the bleed air flow to the turbocompressor turbine. The TC has two functions.

The TC discharge air from the compressor section increases the flow of the bleed air that goes to the primary heat exchanger and the Air Separation Unit(ASU). This occurs at lower pneumatic system pressures with the engines at lower power settings.

Discharge air from the TC goes to the regen heat exchanger. This cooler bleed air goes through the regen heat exchanger to the compressor section inlet of the TC.

Turbocompressor Shutoff Valve Operation

The valve works by using the differential pressure between ambient and the in-line valve pressure. A 28v dc solenoid valve on the side of the main valve selects the valve position. The TCSOV is normally spring-loaded closed. It energizes open by the NGSC. With the TCSOV closed, normally during climb and cruise, all of the air that goes to the TCU goes through the ozone converter. The air then goes to the primary heat exchanger inlet, and next to the heatexchanger bypass. This is the non-boosted mode. When the TCSOV opens, normally during descent and ground operations, some of the bleed air from the NGS SOV goes to the turbine inlet port of the TC. Here, the air expands in the turbine which then turns the compressor in the turbocompressor. The bleed air that goes into the compressor comes from the regen heat exchanger. The high pressure air that comes out of the turbocompressor forces the turbocompressor check valve to close. This prevents a back flow of the boosted air towards the NGS shutoff valve and into the aircraft bleed air system.

Airflow that comes out of the TC turbine cools through expansion. This cool air goes through the opposite side of the regen heat exchanger. This air then precools the air entering the compressor section of the turbocompressor. This is the boosted mode.

The NGSC will close the TCSOV if the TC compressor outlet temperature becomes more than 465F (241C). The NGSC also closes the TCSOV when it shuts down the NGS.



NGS - TURBOCOMPRESSOR AND TURBOCOMPRESSOR SHUTOFF VALVE

TURBOCOMPRESSORCOMPRESSOR SECTION



NGS - REGEN HEAT EXCHANGER

Purpose

The Nitrogen Generation System (NGS) regen heat exchanger precools the bleed air before it goes into the compressor section of the Turbocompressor (TC). The TC compressor discharge air goes to the primary heat exchanger. The regen heat exchanger controls the maximum temperature of the airflow going to the primary heat exchanger.

Operation

The Turbocompressor Shutoff Valve (TCSOV) normally opens during boosted system operation. Boosted system operation occurs when pneumatic system bleed pressures are low. The bleed pressure is normally lower at lowerengine power settings.

When the TCSOV opens, part of the bleed air from the NGS Shutoff Valve (SOV) goes to the inlet port of the TC. The remaining air goes through the ozone converter and the regen heat exchanger. The air then goes intothe compressor inlet of the TC. The temperature of the airflow through the turbine decreases through energy conversion and expansion. This cool air goes through the opposite side of the regen heat exchanger. This air precools the air that goes into the compressor.

Hot air from the engine bleed system goes into the regen heat exchanger. Cool turbine exhaust air in the regen heat exchanger core decreases the temperature of the air before it goes into the compressor inlet. The cool air flow comes from air that expands in the TC turbine section. This decreases the temperature and the pressure of the air that goes to the primary heat exchanger. This temperature controlled air then goes to the Overtemperature Shutoff Valve (OTSOV) in the Air Separation Unit (ASU).



NGS - REGEN HEAT EXCHANGER

TURBOCOMPRESSORCOMPRESSOR SECTION



NGS - COMPRESSOR OUTLET TEMPERATURE SENSOR AND THERMAL SWITCH

Compressor Outlet Temperature Sensor Purpose

The Compressor Outlet Temperature Sensor (COTS) measures the temperature of the bleed air that comes out of the Turbocompressor (TC). The temperature information is used for system fault detection by the Nitrogen Generation System Controller (NGSC).

Location

The COTS is on the outlet duct of the compressor section of the turbocompressor. The duct is part of the Thermal Control Unit (TCU).

General Description

The temperature sensor is a dual element probe unit with an electrical connector. It is sealed in a corrosion resistant stainless steel body. The NGSC uses the COTS to monitor the air temperature of the turbocompressor outlet. The COTS is part of a bridge circuit in the NGSC. When the measured temperature goes more than 465F (241C), the NGSC controller closes the Turbocompressor Shutoff Valve (TCSOV). The NGSC will also set one or more fault messages that can show on the BITE Display Unit (BDU) display.

Thermal Switch Purpose

The Thermal Switch (TS) monitors outlet air temperature of the Turbocompressor (TC) outlet temperature. The thermal switch can close the Turbocompressor Shutoff Valve (TCSOV). The TCSOV closes for high TC compressor outlet temperature.

The TS gives a backup to the Nitrogen Generation System Controller (NGSC) to close the TCSOV. If the NGSC cannot close the TCSOV for high temperature, the TS will open to cause the TCSOV to close. The NGSC will also close the TCSOV when the NGS operates in the boosted mode for overpressure.

General Description

The thermal switch is in the Thermal Control Unit (TCU). The thermal switch is a bimetallic type of switch. The switch is in the control circuit from the NGSC to the TCSOV.

Functional Description

The normal position of the thermal switch electrical contacts are closed. The contacts opens with a sensing element temperature of 465-485F (241-252C). The thermal switch resets when the temperature goes less than 450F(232C).

The thermal switch contacts connect in series with the excitation coil of the TCSOV. The open switch contacts cause the TCSOV excitation power to be removed. The TCSOV goes to the closed position.



NGS - COMPRESSOR OUTLET TEMPERATURE SENSOR AND THERMAL SWITCH



NGS - AIR FILTER AND DIFFERENTIAL PRESSURE SWITCH

Air Filter Purpose

The air filter removes the following particulate and aerosol materials that are in the bleed air:

• Dust • Sand • Oil • Hydraulic fluid • Water

The filter helps to prevent contamination of the air separation modules.

Location

The filter is in-line in the pneumatic duct between the Thermal Control Unit (TCU) and the Air Separation Unit (ASU). The filter is in the right ram air ductcompartment.

Air Filter

The filter assembly is a two stage design. The filter can remove contaminant particles one micron and higher in size. The filter has an inner coalescer stage and an outer pleated filter pack. These are the two stages of the filter:

• The coalescer stage is made from layers of very high efficiency glass fiber, polyester and stainless steel, all pleated together into a filter pack.

• The outer pleated filter pack is similar in construction. It ensures that the whole filter element provides high efficiency particulate and periodic fluid protection to downstream components

The primary and secondary drain poppet valves are at the bottom of the filter. The primary and secondary drain valves let fluid contaminants leave both stages of the filter. The valves are normally spring-loaded closed. The drain poppet lets water and other fluids to go out of the filter housing. Push the valves to the open position to let contaminants out of the filter housing.

Differential Pressure Switch Purpose

The Nitrogen Generation System Controller (NGSC) uses the differential pressure switch to monitor the condition of the Nitrogen Generation System (NGS) air filter.

Filter Differential Pressure Switch

The filter differential pressure switch measures the differential pressure across the filter. The switch has two sensing ports. The ports are the high pressure sense port and the low pressure sense port. The high pressure port connects to duct upstream of the filter. The low pressure port connects to the duct downstream of the filter. A pressure difference of more than 1.2 psid across the filter operates the switch. This shows that the filter is clogging. The NGSC closes the NGS Shutoff Valve (NGS SOV) and the Overtemperature Shutoff Valve (OTSOV). With these valves closed, the NGS operation stops. The differential pressure signal goes to the NGSC. The NGSC sends a filter clogged indication to the BITE Display Unit (BDU).



NGS - AIR FILTER AND DIFFERENTIAL PRESSURE SWITCH



NGS - AIR SEPARATION UNIT

General Description

The Air Separation Unit (ASU) frame assembly contains the related ASU components, related tubes and ducts. The assembly connects to the airplane forward of the right ECS bay. These are the components of the ASU:

• Frame assembly • ASU inlet temperature sensor • Thermal switch • Overtemperature shutoff valve (OTSOV) • Air separation modules (ASM) (3) • Oxygen sensor • High flow valve • Differential pressure sensor • High flow orifice • Low flow orifice

The ASU inlet temperature sensor monitors the bleed air temperature from the Temperature Control Unit (TCU). The OTSOV closes to protect the ASU components and center wing fuel tank from damage. The Nitrogen Generation System Controller (NGSC) or the thermal switch can close the OTSOV.

The ASU has three ASMs. The bleed air oxygen molecules are separated from the nitrogen molecules as the air goes through the ASMs. The Oxygen Enriched Air (OEA) goes overboard. The nitrogen enriched air (NEA) goes to the center fuel tank.

The oxygen sensor measures how much oxygen is in the NEA.

When increased NEA is needed, the high flow valve will open. The differential pressure sensor monitors the position of the high flow valve.

The high and low flow orifices give measured NEA flow to the distribution system.

Operation

The key control and monitoring functions of the Air Separation Unit (ASU) are:

• Give NEA for distribution to the fuel tanks • Give low or high flow upon command from the NGSC • Give temperature sensing for control of the bleed air that goes into the

ASMs • Give thermal protection from excessive bleed air temperature • Give oxygen concentration data to the NGSC for fault detection • Give flow control monitoring



NGS - AIR SEPARATION UNIT



NGS - OVERTEMPERATURE SHUTOFF VALVE, THERMAL SWITCH AND INLET TEMPERATURE SENSOR

Overtemperature Shutoff Valve Purpose

The Overtemperature Shutoff Valve (OTSOV) gives backup protection for the Air Separation Modules (ASM) if there is a controller failure. It supplies a secondary means to shut the system down.

General Description

The OTSOV is the same valve as the Turbocompressor Shutoff Valve (TCSOV).

The OTSOV is in the Air Separation Unit (ASU), upstream from the three ASMs.

The valve is electrically controlled and pneumatically operated. It is spring loaded to the closed position. The Nitrogen Generation System Controller (NGSC) controls the valve during normal operations. The controller de-energizes the valve when the system is off.

These are the parts of the overtemperature valve:

• Electric connector • Solenoid • Valve body

If the controller does not close the OTSOV when the temperature is too high, the thermal switch deenergizes the solenoid. It does this independently fromthe controller. This causes the OTSOV to close.

Operation

At the start of NGS operation the NGSC energizes the OTSOV solenoid and the valve opens. Air from the Temperature Control Unit (TCU) goes through the valve to the ASMs. The air that leaves the OTSOV first goes past a thermal switch and the air separation module inlet temperature sensor.

The NGSC monitors the air temperature going to the ASMs using the temperature sensor. If the air temperature at the ASU inlet temperature sensor goes to 255F (107C) the NGSC will de-energize the OTSOV solenoid. The OTSOV will close. The NGSC will also close the NGS shutoff valve (SOV).

Note: The NGSC also uses the temperature sensor air temperature for normal control of the Temperature Control Valve (TCV) in the TCU

The thermal switch gives a back up to the temperature sensor if the NGSC does not close the OTSOV for high temperature. The thermal switch opens at 275F (135C). When the thermal switch opens it removes the power that goes to the solenoid of the OTSOV. The OTSOV solenoid de-energizes and the valve closes. The thermal switch resets when the temperature at the switch goes to atemperature of 255F (124C).

Thermal Switch Purpose

The thermal switch works with the Overtemperature Shutoff Valve (OTSOV) to make sure that the maximum air temperature is less than 280F (138C).

General Description

The thermal switch electrically connects to the OTSOV. The thermal switch sends a close signal to the OTSOV when an overheat condition is detected.

The normal position of the thermal switch electrical contacts are closed. The contacts open when temperature at the sensing element goes to between 255 and 275F (124C - 135C). The thermal switch resets when the temperature goes down to 205F (96C)

The thermal switch contacts are in series between the power supply and the excitation coil of the OTSOV. The NGSC has the ground for the excitation coil. When the contacts open the OTSOV excitation power is removed and the OTSOV goes to the closed position.

Function

The switch is a backup to the Air Separation Module (ASM) inlet temperature sensor. When the temperature measured by the sensor is more than 235F (113C), the NGSC will open the 28v dc return power or ground to the OTSOV. The solenoid coil de-energizes causing the OTSOV to close. The ASM inlet temperature sensor and ASM inlet thermal switch are both located in the same duct in between the OTSOV and the ASM inlet ports. If the temperature is more than 235F (113C) and the OTSOV remains closed because of a NGSC control. control.lt, the thermal switch will open.



NGS - OVERTEMPERATURE SHUTOFF VALVE, THERMAL SWITCH AND INLET TEMPERATURE SENSOR



NGS - OVERTEMPERATURE SHUTOFF VALVE, THERMAL SWITCH AND INLET TEMPERATURE SENSOR (CONT)

Purpose

The air separation unit inlet temperature sensor measures the temperature of the bleed air that goes into the ASM.

Description

The temperature sensor is a dual-element, platinumtype, nominal at 32F (0C) RTD sensor. The sensor can measure temperatures from -67F to 500F(-55C to 260C). The temperature sensor is part of a bridge circuit in the Nitrogen Generating System Controller (NGSC).

Location

The temperature sensor is in the duct between the Overtemperature Shutoff Valve (OTSOV) and the Air Separation Modules (ASM) inlet. The sensor is in the Air Separation Unit (ASU).

General Description

Each element of the dual-element sensor is a thermal resistive device. The resistance changes in proportion to the temperature of the element. The NGSC measures the resistance of the element and converts this resistance to degrees celsius or degrees fahrenheit. The NGSC uses the temperature sensor for control of the Temperature Control Valve (TCV). The NGSC also uses thesensor for system fault detection and overtemperature control.



NGS - OVERTEMPERATURE SHUTOFF VALVE, THERMAL SWITCH AND INLET TEMPERATURE SENSOR (CONT)



NGS - AIR SEPARATION MODULE

Purpose

The Air Separation Modules (ASM) take oxygen from the bleed air in the Nitrogen Generation System (NGS).

Location

The ASMs are in the right ram air duct compartment, forward of the ECS bay. They are in the Air Separation Unit (ASU).

General Description

The ASMs use bleed air to make Nitrogen Enriched Air (NEA) for the center fuel tank. The ASMs remove the oxygen from the bleed air. The oxygen removed from the bleed air is Oxygen Enriched Air (OEA). The OEA goes overboard through a port on the ASM. The remaining air is Nitrogen Enriched Air (NEA). NEA goes from the outlet port through the distribution system to the center fuel tank.

The ASMs are made of porous fiber membrane bundles in an aluminum housing. The inlet and outlet fittings are flexible couplings that connect to bleed air supply and NEA outlet ducts. The OEA port is also a flexible coupling.

Both the inlet and outlet surfaces of the fiber bundle are sealed against the housing to prevent air bypassing the bundle. Bleed air enters the bundle through the inlet manifold. As the air goes through the bundle, oxygen is separated through the fiber walls. The OEA goes overboard through the OEA port. Carbon dioxide and water molecules separate with the oxygen molecules. The remaining NEA goes through the outlet port towards the NEA distribution system.

The major driver of nitrogen enriched air quality is the pressure difference between inlet bleed air pressure and oxygen enriched air pressure.

Operation

The ASMs enable the generation of NEA that goes to the center fuel tank. The units operate normally at an ambient temperature of 170F (77C). The main factor of NEA quality is the pressure difference between inlet bleed air pressure

and OEA pressure. The hollow fiber membrane ASM makes better NEA with the same inlet pressure (psia) at high altitude compared to sea levelconditions.

The system includes three ASM units in parallel with each other. The ASMs are in the ASU frame assembly. The ASMs are connected to each other through the bleed air, NEA and OEA ducting.



NGS - AIR SEPARATION MODULE



NGS - HIGH FLOW VALVE AND OXYGEN SENSOR

High Flow Valve Purpose

The high flow valve causes the increase of the amount of Nitrogen Enriched Air (NEA) flow to the center fuel tank.

Location

The high flow valve is in the right ram air duct compartment, forward of the ECS bay. It is part of the Air Separation Unit (ASU).

General Description

The high flow valve is solenoid controlled and pneumatically operated. It is a sliding gate valve. The valve spring loads to the closed position.

With the solenoid de-energized, the valve vents pressure behind the piston through the solenoid to ambient. Spring pressure moves the valve gate to theclosed position. The NEA is in low flow.

With the solenoid energized, inlet air pressure goes to the actuator piston through the solenoid valve. Air pressure on the piston overcomes spring pressure. This opens the gate to the open position.

Note: The valve visual position indicator retracts with the valve closed. The indicator extends with the valve open.

Operation

The Nitrogen Generation System Controller (NGSC) sends a discrete voltage signal to open the high flow valve. The NGSC uses the high-flow valve select high-flow operation.

During normal operation, high flow happens during descent, and also during maintenance operation. High flow also happens during ground operations following a system restart. With the high-flow valve open, a parallel flow path to the fuel tank activates. This allows increased NEA flow for descent operation. With the high-flow valve closed, this additional path is not used.

With the valve closed, NEA is in low flow. The NGS low flow mode occurs in the climb and cruise segments of flight. Low flow also occurs during ground operation of the NGS. The NGSC sends a command to operate the turbocompressor for NGS ground operations. NGS operates in low flow, boosted mode on the ground.

The NGSC uses a differential pressure sensor to measure the NEA flow across the high flow orifice. The NGSC uses differential pressure data for high flow valve fault detection.

Oxygen Sensor Purpose

The oxygen sensor measures the oxygen content and absolute pressure of the Nitrogen Enriched Air (NEA). This information is sent to the Nitrogen Generation System Controller (NGSC). The oxygen sensor monitors the performance of the Air Separation Modules (ASM). The ASMs are in the Air Separation Unit (ASU).

Location

The oxygen sensor is in the right ram air duct compartment, forward of the ECS bay. It is part of the ASU.

General Description

The oxygen sensor measures the oxygen content and absolute pressure of the NEA supply gas. The sensor sends the data to the NGSC, which uses the data for system status. The sensor normally operates once per flight leg with command from the NGSC. The NGSC normally sends the command at the first part of cruise flight.

Operation

The NGSC starts a timer at takeoff, when the airplane goes into the air. After thirty minutes the NGSC sends the command for the sensor to start to operate. The oxygen sensor starts a five minute warm up period. After five minutes the oxygen sensor gets NEA samples from the common manifold downstream from the three ASMs. The NGSC compares the oxygen sensor output to an expected value of oxygen concentration. Airplane pressure and altitude determines this expected value. The NGSC uses this data for system status monitoring. If the first reading was unsuccessful one more attempt will be made at top of descent.



NGS - HIGH FLOW VALVE AND OXYGEN SENSOR



NGS - DIFFERENTIAL PRESSURE SENSOR AND FLOW ORIFICES

Purpose

The Nitrogen Generation System Controller (NGSC) uses the differential pressure sensor to test the high flow valve. The sensor detects the pressure change when the valve is open or closed.

General Description

The pressure sensor measures differential pressure across the high flow orifice before the nitrogen enriched air is sent to the center fuel tank. The NGS controller provides electrical excitation for the sensor. The sensor sends a voltage output to the NGS controller relative to the pressure being sensed.

The sensor is connected between the upstream and downstream sides of the high flow orifice.

The high and low flow orifices ensure that a specific NEA flow rate is maintained for the different NGS flow modes.

Operation

The sensor contains a silicone strain gauge for pressure sensing. The sensing elements and the electronics are protected inside a stainless steel housing.

The NGSC sends a nominal 28v dc excitation signal to the sensor. The sensor sends a voltage output between 0.5v dc and 10.5v dc back to the NGSC. This variable voltage is proportional to a differential pressure of 0 to 45 psid. The NGSC reads the variable voltage return and converts it to engineering units of psid.



NGS - DIFFERENTIAL PRESSURE SENSOR AND FLOW ORIFICES



NGS - DISTRIBUTION SYSTEM GENERAL DESCRIPTION

Purpose

The Nitrogen Enriched Air Distribution System (NEADS) sends the Nitrogen Enriched Air (NEA) to the center fuel tank. The system also makes sure that outside air does not cross flow into the center tank.

Location

The distribution system components are in these areas:

• Forward right hand wing to body fairing • Right hand leading edge • Center wing fuel tank • Left hand surge tank

Physical description

The NEA distribution system has these components:

• Cross vent check valve • Backflow prevention check valve (2) • Float valve • Distribution manifold • Insulator tube • Sump drain valve • NEA ejector tube

Operation

The NEADS has a distribution manifold, which sends the NEA from the Air Separation Unit (ASU) into the center wing fuel tank. There are two backflow check valves. The check valves keep fuel from going into the distribution manifold and ASU.

Use the sump drain valve to remove fuel from distribution manifold. The valve is at the low point in the system. Push the valve in to remove the fuel. The insulator tube is a 1 inch (2.5 cm) non-conductive tube. The tube prevents lightning current from entering the fuel tank. The flame arrestor prevents too

much heat from going through the center tank front spar. This helps to prevent an auto ignition of the fuel vapor and air mixture in the center tank.

The NEA ejector tube connects the distribution manifold to the vent system in the center fuel tank. The ejector sends NEA forward to the right climb vent portion of the tube.

The float valve connects to the left hat-section vent channel on the right side of the center tank. The float valve opens when the center fuel tank is not full. Theopen valve gives even NEA distribution to the center tank. With the valve open, NEA will go from the left center tank area into the hat-section vent channel, then to the right vent tube. The NEA will then go back into the right center tank area.

The cross vent check valve does not let outside air dilute the NEA in the center fuel tank. The check valve will not let air go between the left and right surge tanks.

Note: The GSE O2 PORT lets test equipment connect to the NGS. This allows testing of the O2 content of the NEA



NGS - DISTRIBUTION SYSTEM GENERAL DESCRIPTION



NGS - DISTRIBUTION SYSTEM COMPONENTS

Float Valve

The float valve helps the supply of Nitrogen Enriched Air (NEA) go through the center fuel tank at low fuel levels. This lets the vent system continue to operate.When the tank is almost full, the float valve closes. This does not let fuel go into the vent system. While the fuel level decreases during flight, the float valveopens. This lets the distribution system supply full circulation of the NEA.

Cross-Flow Vent Check Valve

The cross-flow vent check valve is a flapper type. The check valve prevents cross flow ventilation of the fuel tank. It is in the left surge tank. The valve isspring-loaded closed, and goes to open at 0.2 to 0.5 psi. This lets the unwanted fuel fumes flow from the vent channel to go to the surge tank. This prevents thedilution of the nitrogen enriched air (NEA) in the center tank with fresh air. Ventilation cross flow usually occurs during refueling operations.

Back flow Prevention Check Valves

The back flow prevention check valves give backflow protection from the center fuel tank. This keeps the center fuel tank fuel out of the air separation unit (ASU).

Drain Valve

You use the drain valve to do a check for fuel or other fluid in the nitrogen generation system (NGS) distribution system tube.

Drain Valve Location

The drain valve is in the distribution system downstream of the Air Separation Modules (ASM) and forward of the air separation unit (ASU). You can get access to the drain through the right side air conditioning bay access door.

General Description

The drain valve has a spring-loaded poppet that you can open with a small hex driver. Make sure you have an approved container to catch fluid from the valve.

Refer to the Airplane Maintenance Manual (AMM) when you do maintenance on the airplane.



NGS - DISTRIBUTION SYSTEM COMPONENTS



NGS - NITROGEN GENERATION SYSTEM CONTROLLER

Purpose

The Nitrogen Generation System Controller (NGSC) controls and monitors the Nitrogen Generation System (NGS). The NGSC also gives an interface to otherairplane systems.

Location

The NGSC is behind the sidewall liner, on the right side of the forward cargo compartment. The NGSC is near the aft bulkhead. The three-point location of the NGSC is STA 984, WL 180 and RBL 87.


The NGSC is inside a compact lightweight chassis. The chassis attaches to the airplane with four shock resistant mounting flanges. The chassis contains onecircuit card assembly, with an integrated power supply.

Functions

Airplane air/ground mode causes the NGSC to operate in different modes. The NGS mode will determine how the NGSC uses these are the functions:

• Regulation of bleed air temperature entering the ASM by modulation of the temperature control valve (TCV)

• Open/closed control of the NGS SOV • Open/closed control of the OTSOV • Open/closed control of the TCSOV • Open/closed control of the HFV • Ground fan control via command of the associated airplane electrical

power relay • Detection of overpressure conditions • Detection of over temperature conditions (time filtered) Backup over

temperature protection also comes from thermal switches • Detection of loss of flow • Oxygen (O2) sensor interface, for air separation module (ASM)

performance degradation detection • BITE of all line replaceable units (LRU)s and interfaces

• ARINC 429 data communication. RS422 communication for software download and controller monitor data

• BITE display unit (BDU) interface • System status display on the operability indicator • Recording of specified data in the non-volatile memory (NVM) at the time of

any failure detection for later review

BITE

The NGSC has different Built-In-Test (BITE) functions. The BITE functions set faults, and isolates LRUs for fault isolation. BITE also records faults for servicehistory records. The NGSC BITE includes these tests:

• Power-up self-test for the central processing unit (CPU) and power supply test

• Start BIT • Continuous BIT • Initiated BIT • Fault recording

Start BIT does a test at the start of flight. This test starts at takeoff by an input from air/ground logic. The test finds failures of the open NGS shutoff valve(NGSOV), over temperature shutoff valve (OTSOV), high flow valve, and monitoring system sensors. The test operates for two minutes.

Continuous BIT occurs at set intervals when the NGSC is in control mode. Continuous BIT starts after the powerup self test bit completes.

Initiated BIT is the test you start from the BITE display unit (BDU).

The NGSC sends recorded fault information detected by BITE to the BDU. The NGSC sends NGS status information to the status indication panel (SIP).



NGS - NITROGEN GENERATION SYSTEM CONTROLLER



NGS - BITE DISPLAY UNIT

Purpose

The BDU is the maintenance connection to the Nitrogen Generation System Controller (NGSC). You use the BITE Display Unit (BDU) to troubleshoot the Nitrogen Generation System (NGS) faults. The BDU also lets you initiate BITE tests in the NGSC. The BDU has no processing capability. The BDU connects with the Nitrogen Generation System Controller (NGSC) over the RS232 digital interface.

Location

The BDU is in the R/H wing to body fairing. The BDU is aft of the R/H wing front spar, at STA 782. You get access through the R/H pressure relief panel near the NGS filter.


The BDU unit has these items:

• BITE instruction plate • The two-line Vacuum Fluorescent Display (VFD) • Membrane type BITE control buttons (6)

BITE

The BDU unit has these selections on the main menu:

• EXISTING FAULTS • FAULT HISTORY • GROUND TESTS • OTHER FUNCTIONS

These are the functions of the BITE control buttons:

• ON/OFF button - turns on and turns off BITE functions • MENU button - used to show the main menu or to move up one level in the

BITE selections • YES button - used to select a main menu item • NO button - used to not select a main menu item

• Up arrow button - use to scroll up through the menu or the results of the BITE test

• Down arrow button - use to scroll down through the menu or the results of a BITE test.



NGS - BITE DISPLAY UNIT



NGS - BITE DISPLAY FUNCTIONS

EXISTING FAULTS

The EXISTING FAULTS menu shows faults that are currently present. You can see faults and fault details from the main menu EXISTING FAULTS. Faults aremaintenance messages of the primary problem. For more information on a fault, there are fault details available.

If there is a fault or faults, the most recent fault shows on the display. To see the next fault, push the NO or DOWN arrow button. If there are no more faults,the display shows BOTTOM OF LIST for 2 seconds.

FAULT HISTORY

The FAULT HISTORY menu shows previous faults that are in Non-Volatile Memory (NVM) that have not been cleared. From the FAULT HISTORY menu, push the YES button. If there are no faults, the display shows NO FAULTHISTORY. To go back to the main menu, push the MENU button.

If there are faults, the display shows FLIGHT 00. To show the next flight leg, push the NO or DOWN arrow button. Then the display shows the next flight leg. If there are no more flight legs in memory, the display shows BOTTOM OF LIST for 2 seconds. The highest number flight leg that can show is FLIGHT 09. The controller can hold up to 10 flight legs in NVM.

GROUND TEST

The GROUND TEST menu lets you do a series of tests of the nitrogen generation system (NGS). From the GROUND TEST menu you push the NO or DOWN arrow button. The display shows the following tests:

• ELECTRICAL TEST • SYSTEM TEST • GSE PERF NON-BOOSTED (low flow mode) • GSE PERF BOOSTED (high flow mode) • DISPLAY TEST

When you select a particular test, the message TEST IN PROGRESS shows.

If there are no faults during the test, the display shows SYSTEM OK. If there is a fault during TESTING, the display shows EXIST FAULTS for 2 seconds. Then the display shows the existing faults menu.

OTHER FUNCTIONS

The OTHER FUNCTIONS menu shows the specifics of the nitrogen generation system.

From the OTHER FUNCTIONS menu push the NO or DOWN arrow button. The display shows the following:

• SYSTEM CONFIGURATION • I/O MONITOR

SYSTEM CONFIGURATION

The SYSTEM CONFIGURATION page gives this information:

• Hardware part number • Software part number • Configuration part number • Aircraft ID 767

I/O MONITOR

The I/O MONITOR page gives this information:

• Analog inputs • Discrete inputs • Valve drivers



NGS - BITE DISPLAY FUNCTIONS

B767 ATA 47 Student Book

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