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C 3 UNIT II ENGINE AUXILIARY SYSTEMS 9 Electronically controlled gasoline injection system for SI engines, Electronically controlled diesel injection system (Unit injector system, Rotary distributor type and common rail direct injection system), Electronic ignition system, Turbo chargers, Engine emission control by three way catalytic converter system. ME 2354

AUTOMOBILE ENGINEERING

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ELECTRONICALLY CONTROLLED GASOLINE INJECTION SYSTEM FOR SI ENGINES: Gasoline Injection: (Petrol Injection) Types of Injection Systems:

(a) According to location of injector: (i) Throttle body injection:

 PEC  –   –  DoME

(ii) Port injection: (multi-port fuel injection system) 

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(iii) Direct injection: 

(b) According to duration and timing of fuel injection. (i) Continuous type  (ii) Intermittent type: (iii) Sequential type: (c) According to number of injectors: i njectors: (i) Single point (or central) injection  (ii) Multi point (or multi port) injection

 PEC  –   –  DoME

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(d) According to control method (i) Mechanical (ii) Electronic: Mechanical Injection:

 PEC  –   –  DoME

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Electronic Fuel injection:

External A/F Mixture fformation: ormation: Single poin pointt injection & Multi P Point oint fuel Injection:

 PEC  –   –  DoME

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Injection system Operating States: Cold starting: starting: Post-start phase: Warm-up phase: Idle and part-load: Full load (WOT(wide-open (WOT(wide-open throttle)): throttle)): Acceleration and deceleration: Requirements of Gasoline injection systems: To supply the engine with the optimal air-fuel mixture for any given operating conditions. Maintaining air-fuel mixtures within precisely defined limits, which translate into superior performance in the areas of fuel economy, comfort and convenience, and power to meet emission norms. Apart from fuel and spark control, most electronically controlled fuel injection engines also control the idle speed by means of a small electric stepper motor, called the Idle Airspeed Control (IAC) motor, which is controlled by ECU. When engine is subjected to additional load, e.g., engaging the air-conditioning compressor or when alternator is subjected to heavy electrical loads, this lAC motor meters additional air into the engine to raise the idle speed. Fig. shows a typical control layout for all electronically controlle controlled d petrol injection system.

MAIN COMPONENTS OF PETROL INJECTION SYSTEMS: Air Meter: Fuel rail:

Tuned flexible injection system:  PEC  –   –  DoME

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Throttle Bodies: 1.  Mechanical type

2. Electronic type type  

Integrated air-fuel modules: Sensors: These are used to provide all the required data from the various components to achieve an efficient engine management.

The common sensors employed are : 1.  Crankshaft speed sensor: sensor: This registers the speed and angle of crankshaft without contact. It may be inductive; differential Hall or Anisotropic Magneto Resistance (AMR) type.  PEC  –   –  DoME

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2.  Camshaft speed sensor: Also called the phase sensor, it measures the speed and position of the camshaft without contact. 3.  Knock sensor: This is used to recognize the onset of knocking using fuels of  varying quality, thereby controlling the knock resulting, apart from engine protection, fuel saving of about 9% and torque increase of 5%. 4.  Mass Air flow sensor to measure quantity of air drawn into the engine. 5.  Manifold absolute pressure (MAP) sensor. 6.  Barometric pressure (BARO) sensor (correction for air density change with height). 7.  Throttle position sensor (TPS) (correction for sluggish movement of fuel droplets during speed transition conditions). 8.  Coolant temperature sensor (CTS) (correction for poor atomization and wall wetting). 9.  Manifold air temperature (MAT) sensor (correction for air density variation with atmospheric temperature). 10. Exhaust Exhaust oxygen sensor (correction for emission control). 11. Distributor Distributor reference pulses (for control of open time of fuel injectors). 12. Vehicle Vehicle speed sensor (VSS). 13. Battery voltage sensor (correction for supply voltage to control unit and injectors). Injector:

Single point injection injector  PEC  –   –  DoME

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Multipoint injection injector 7 

 

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Disadvantages of Manifold injection: Problems may occur at idling because of incomplete fuel evaporation due to low air flow velocity into cylinder Distribution of air flow into different inlet pipes may vary. Amount of fuel injected is less accurate at id idling ling because electromagnetic injection valves are time controlled. There is a large impact on amount of fuel injected at small injection times. DI-MOTRONIC SYSTEM The Bosch system for direct injection in petrol engines is shown in Fig.

DI-Motronic DI-Motron ic Direct gasoline injection

 PEC  –   –  DoME

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Electronically controlled diesel injection system (Unit injector system, Rotary distributor type and common rail direct injection system) INTRODUCTION:   Fuel supply system in a diesel engine has to perform certain functions. These functions along with the names of the components which perform the same are given below: 1.  Storing of fuel: Fuel tank is usually positioned along the side of the vehicle chassis. 2.  Filtering: Water and dirt must be removed from the diesel for which two filters f ilters are employed. Primary filter is usually in the form of a coarse wire gauze and is often optional. It prevents large solid particles and water from going to the fuel feed pump. Secondary filter is used after the fuel feed pump and is meant to remove fine particles of dust, dirt etc. from the diesel which is to go to the injection pump. 3.  Delivery of fuel to injection pump: From the fuel tank the fuel is delivered to the fuel injection pump by means of fuel feed pump. The rate of fuel delivery depends upon the engine requirements. 4.  Injecting the fuel into engine cylinders:  cylinders:   Exact amount  of fuel is metered, atomized and injected under high pressure to each cylinder in correct sequence and at the correct moment  according to the engine requirements. This is done by means of a fuel injection pump in conjunction with injectors for each cylinder. Extra strong steel pipes transmit the metered, pressurized and timed fuel from the fuel injection pump to each injector. 5.  Controlling the engine speed: Diesel engine speeds tend to overshoot to dangerous values on reduction of load. This is controlled by means of a governor, which besides limiting maximum speed also regulates the fuel supply under all conditions.

FUEL INJECTION SYSTEM:

 PEC  –   –  DoME

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Mechanical Common rail fuel injection system:

Mechanical Individual Pump Fuel Injection System:

 PEC  –   –  DoME

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MODERN ELECTRONIC COMMON RAIL FUEL INJECTION SYSTEM:

 LAYOUT OF BOSCH K5-CR SYSTEM FOR PASSENGER CAR ENGINES 

 PEC  –   –  DoME

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 PEC  –   –  DoME

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Unit - 2 1. Leak off port 2. Leak off cap 3. Injector Spring 4. Lower spring plate 5. Clamping Flange 6. Nozzle Holder 7. Fuel Gallery 8. Tapered needle shoulder 9. Nozzle Body 10. Spray Holes 11. Nozzle Tip 12. Needle and Nozzle seat 13. Needle Valve 14. One of 3 feed holes 15. Supply Hole 16. Spindle 17. Inlet Port 18. Spring cap adjustment nut 

 PEC  –   –  DoME

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Bosch Third Generation CRS  CRS 

UNIT INJECTOR SYSTEM:

 PEC  –   –  DoME

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 PEC  –   –  DoME

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Operating states: a) Suction stroke, b) Initial stroke, c) Prestroke, d) Residual stroke. 1.  Actuating cam, 7.  Feed passage, 2.  Pump plunger, 8.  Fuel-return passage, 3.  Follower spring, 9.  Coil, 4.  High-press High-pressure ure chamber, 10. Solenoid-valve Solenoid-valve seat, 5.  Solenoid-val Solenoid-valve ve needle, 11. Nozzle Nozzle assembly. 6.  Solenoid-valve chamber,

1. Fuel inlet 2.   Fuel return 3.  Injector 4.  Injector spring 5.  Pump plunger 6.  Pushrod 7.  Pushrod return spring 8.  Solenoid 9.  Solenoid valve

 PEC  –   –  DoME

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 PEC  –   –  DoME

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Unit Pump System:

 PEC  –   –  DoME

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Electronically-controlled Electronicall y-controlled Rotary distribu distributor tor fuel injection:

 PEC  –   –  DoME

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 PEC  –   –  DoME

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 PEC  –   –  DoME

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 Electronic Ignition Ignition Systems Introduction:   Although the conventional mechanical contact breaker point type electrical ignition system has been very common in use because of its simplicity, yet due to its drawbacks and limitations the same is being fast replaced by the electronic ignition system.

Principle of distributor type electronic ignition:

Comparison of the primary circuit of a contact point ignition system with that of an Electronic ignition system .

 PEC  –   –  DoME

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Components in an electronic ignition using a pickup-coil distributor, with a simplified electronic  control module module (ECM). (ECM). The pickup-coil pickup-coil voltage voltage signal is shown at the lower right.

Pulse generator:  generator: 

Hall-effect switch:

 PEC  –   –  DoME

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 Fig. Ignition Ignition distributor distributor using a Hall-effe Hall-effect ct switch (A) (A) The window window is passing passing through through the air gap. gap. The magnetic field, or flux, from the permanent magnet is imposed on the Hall-effect sensor. (B) The  shutter is in in the air gap. gap. This cuts off off the flux, flux, preventing preventing the magnetic magnetic field-from field-from acting on on the HallHalleffect sensor 

 Fig. Hall-effect Hall-effect switch-The switch-The shutter shutter width  determines dwell, or how how long current current flows in  the primary primary 

 Distributor with a Hall-effec  Distributor Hall-effectt switch mounted  mounted   above the the pickup-coil pickup-coil assembly. The The pickup  coil provides provides the signal signal to fire the the spark plugs plugs  during cranking. cranking.

Optical switch:

 Fig . Photodiode , or optical, optical, distributor distributor which uses uses the on off off action of of a light beam beam to control control the  primary circuit circuit  PEC  –   –  DoME

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Distributorless Ignition:   This type of electronic ignition system was introduced in mid 1980s which does not have a  separate ignition distributor. distributor. 

 Fig. Distributorless Distributorless ignition system, system, which which does not have a separate separate ignition ignition distributor. distributor.

 Fig. Schematic Schematic of distributorles distributorlesss ignition system system for for a V-6 engine, engine, showing how how three ignition ignition coils coils can  fire six spark spark plugs.

 PEC  –   –  DoME

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 Fig. Spark plugs firing at the same point of each  revolution in two cylinders. cylinders.   Fig. Waste-spark method of spark distribution, showing how  the ignition-coil secondary secondary winding can fire two plugs at once once 

 Fig. One coil firing two spark spark plugs in cylinders that are are piston pairs. The pistons go up and down together, but on  different strokes of the four-stroke four-stroke cycle. One spark is wast wasted. ed. 

Distributorless direct ignition Distributorless   Some engines have a direct ignition system that eliminates spark-plug cables which uses no  spark-plug  spark-plu g cables, on a four-cylinder four-cylinder engine. engine.

 PEC  –   –  DoME

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Direct capacitor discharge ignition:

 Fig. Capacitor-disch Capacitor-discharge arge ignition ignition  system. Each Each spark plug plug has its  own ignition ignition coil and capacitor capacitor that  fit into an ignition ignition cartridge cartridge that that  mounts over over the spark plug. plug.

 Fig. Layout Layout of capacitor-disch capacitor-discharge arge ignition, ignition, showing showing  the ignition cartridge. cartridge. The spark spark occurs when when a switch switch  or transistor transistor closes the the primary circuit. This This allows the the  capacitorr to discharge  capacito discharge through the ignition ignition coil and   produce the the high-voltage high-voltage spark. spark.

  Electronic capacitor discharge ignition (CDI) systems have been common on large industrial

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engines because the technology has been in use since the 1960's. An advantage of the capacitor discharge ignition system is that the energy storage and the   voltage ‘step up' functions are accomplished by separate circuit elements allowing each one to be optimised for its job. Capacitive discharge ignition systems work by storing energy in an external capacitor, which is   then discharged into the ignition coil primary winding when required. This rate of discharge is much higher than that found in inductive systems, and causes a   corresponding increase in the rate of voltage rise in the secondary coil winding.

  This faster voltage rise in the secondary winding creates a spark that can allow combustion in an

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engine that has excess oil or an over rich fuel air mixture in the combustion chamber. The high initial spark voltage avoids leakage across the spark plug insulator and electrodes caused by fouling, but leaves much less energy available for a sufficiently long spark duration; this may not be sufficient for complete combustion in a lean burn turbocharged engine resulting in misfiring and high exhaust emissions. The high voltage power supply required for a capacitor discharge system can be a disadvantage, as this supply provides the power for all ignition firings and is liable to failure.  Ignition in lean fuel mixtures by capacitor discharge systems can sometimes only be accomplished by the use of multi-spark ignition, where the ignition system duplicates the prolonged spark of inductive spark systems by sparking a number of times during the cycle. This adds greater stress onto the high-tension leads and can cause considerable spark plug wear and possible failure. 

 PEC  –   –  DoME

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  TURBO CHARGERS:

 PEC  –   –  DoME

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Exhaust pollutants:  pollutants:    The most important chemical reaction in a petrol engine  –  that is, the one that provides the energy to drive the vehicle – is the combustion of fuel in air.   In an ‘ideal’ system, combustion would be complete so that the o nly exhaust products would be carbon dioxide and steam.   In practice, the complete oxidation of the fuel depends on a number of factors: o  First, there must be sufficient oxygen present; second, there must be adequate mixing of the petrol and air; and o  Finally, there must be sufficient time for the mixture to react at high temperature before the gases are cooled.   The main by-products of combustion are: o  Nitrogen gas (N ): Our atmosphere is 78 percent nitrogen gas, and most of this 2 passes right through the car engine. o  Carbon Dioxide (CO ): A harmless, odorless gas composed of carbon and oxygen. 2 It is also a greenhouse gas that contributes to global warming. o  Water vapor (H O): Another by-product of combustion. The hydrogen in the fuel 2 bonds with the oxygen in the air.   These three emissions are mostly harmless, although carbon dioxide emissions are believed to contribute to global warming.

Distribution Distributio n of emission emissionss by sources (petrol engine powered vehicles) vehicles)    PEC  –   –  DoME

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  Regardless

of how perfect the engine is operating, there will always be some harmful byproducts of combustion since the combustion process is never perfect. o  Carbon monoxide (CO): A colorless, odorless gas. It is poisonous and extremely dangerous in confined areas, building up slowly to toxic levels without warning if  adequate ventilation is not available. o  Hydrocarbons or volatile organic compounds (VOCs): Any chemical compound made up of hydrogen and carbon. o  Oxides of nitrogen (NO ): Chemical compounds of nitrogen, they combine with x hydrocarbons to produce smog.   These are the three main regulated emissions, and also the ones that catalytic converters are designed to reduce.   In internal combustion engines, the time available for combustion is limited by the engine’s cycle to just a few millisecon milliseconds. ds.   There is incomplete combustion of the fuel and this leads to emissions of the partial oxidation product, carbon monoxide (CO), and a wide range of volatile organic compounds (VOC), including hydrocarbons (HC), aromatics and oxygenated species.   These emissions are particularly high during both idling and deceleration, when insufficient air is taken in for complete combustion to occur.   Another important result of the combustion process, particularly during acceleration, is the production of the oxides of nitrogen  –  nitric oxide (nitrogen monoxide, NO) and nitrogen dioxide (NO2).   Conventionally, these two oxides of nitrogen are considered together and represented as NO x.   At the high temperatures involved (in excess of 1500 °C) nitrogen and oxygen in the air drawn in with the fuel may combine together to form NO.   These pollutants can cause severe damage to human health.  PEC  –   –  DoME

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  The

role of an emission control catalyst is to simultaneously remove the primary pollutants CO, VOCs and NO x by catalyzing their conversion to carbon dioxide (CO 2), steam (H2O) and nitrogen (N2).

Three Way Catalytic Converter (TWC):   Essentially, the catalytic converter is used to complete the oxidation process for hydrocarbon (HC) and carbon monoxide (CO), in addition to reducing oxides of nitrogen (NOx) back to simple nitrogen and carbon dioxide. cars today are equipped with a three-way catalytic converter.   Catalytic Converter is located in-line with the exhaust system and is used to cause a desirable chemical reaction to take place in the exhaust flow.   The term Three-way refers to the three emissions it helps to reduce, carbon monoxide, hydrocarbons or volatile organic compounds (VOCs) and NOx molecules.   The converter uses two different types of catalysts, a reduction catalyst and an oxidization catalyst. Both types consist of a base structure coated with a catalyst such as platinum, rhodium and/or palladium.   The scheme is to create a structure that exposes the maximum surface area of the catalyst to the exhaust flow, while also minimizing the amount of catalyst required.   Most

TWC Construction:   Two different types of Three-Way Catalytic Converters have been used on fuel injected vehicles.   Some early vehicles used a palletized TWC that was constructed of catalyst coated pellets tightly packed in a sealed shell.   Later model vehicles are equipped with a monolith type TWC that uses a honeycomb shaped catalyst element.   While both types operate similarly, the monolith design creates less exhaust backpressure, providing ample surface area   while The Three-Way Catalyst, which

to convert feed gases. the actual feed gas is efficiently responsible for performing conversion, is created by coating the internal converter substrate with the following key

 PEC  –   –  DoME

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materials: • Platinum/Palladium: Oxidizing catalysts for HC and CO  • Rhodium: Rhodium: Reducing ca catalyst talyst ffor or NOx  • Cerium: Promotes oxygen storage to improve oxidation efficiency   The inside of the catalytic converter is a honeycomb set of passageways or small ceramic beads coated with catalysts.

 A three-way three-way catalytic catalytic converter converter using a monolith or or honey comb comb coated with with catalyst. catalyst.

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  A There are many passages for the exhaust gases to flow, to allow for the maximum amount of surface area for the hot gases to pass.

TWC Operation:   A chemical reaction takes place to make the pollutants less harmful.   The diagram below shows the chemical reaction that takes place inside the converter.   As engine exhaust gases flow through the converter passageways, they contact the coated surface which initiates the catalytic process.   As exhaust and catalyst temperatures rise, the following reaction occurs: 1.  Reduction of nitrogen oxides to nitrogen and oxygen: 2NO x → xO2 + N2   PEC  –   –  DoME

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2.  Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2  3.  Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

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The Reduction Catalyst:   The reduction catalyst is the first stage of the catalytic converter.   It uses platinum and rhodium to help reduce the NOx emissions.   When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O 2.   The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. Oxidation Catalysts:   Palladium (Pd) and platinum (Pt) metals in very small amounts convert the hydrocarbons of unburned gasoline and carbon monoxide to carbon dioxide and water. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas.   These three reactions occur most efficiently when the catalytic cata lytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.8 and 14.9 parts air to 1 part fuel, by weight, for gasoline   When

there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction.   When there is excessive fuel, then the engine is running rich. The reduction of NO x is favoured, at the expense of CO and HC oxidation. TWC Degradation:   Catalyst operating efficiency is greatly affected by two factors; operating temperature and feed gas composition.   The catalyst begins to operate at around 550' F.; however, efficient purification does not take place until the catalyst reaches at least 750' F.   Also, the converter feed gasses (engine-out exhaust gases) must alternate rapidly between high CO content, to reduce NOx emissions, and high O 2 content, to oxidize HC and CO emissions.   There are many different factors that can cause TWCs demise.  PEC  –   –  DoME

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  Poor engine performance as a result of a restricted converter. Symptoms of a

o

restricted converter include; loss of power at higher engine speeds, hard to start, poor acceleration and fuel economy. o  A red hot converter indicates exposure to raw fuel causing the substrate to overheat. This symptom is usually caused by an excessive rich air/fuel mixture or engine misfire. If the problem is not corrected, the substrate may melt, resulting in a restricted converter. o

egg odor results from excessive hydrogen sulfide production and is   Rotten typically caused by high fuel sulfur content or air/fuel mixture imbalance. If the

problem is severe and not corrected, converter meltdown and/or restriction may result. Causes of TWC Contamination:   The most common cause of catalytic converter failure is contamination. Examples of  converter contaminants include: o  Overly rich air/fuel mixtures will cause the converter to overheat causing substrate meltdown. o  Leaded fuels, even as little as one tank full, may coat the catalyst element and render the converter useless. o

  Silicone from sealants (RTV, etc.) or engine coolant that has leaked into the

exhaust may also coat the catalyst and render it useless.   There are other external factors that can cause the converter to degrade and require replacement. o  Thermal shock occurs when a hot converter is quickly exposed to cold temperature (snow, cold fuel, etc.), causing it to physically distort and eventually disintegrate. o  Converters that have sustained physical damage (seam cracks, shell puncture, etc.) should also be replaced as necessary.

 PEC  –   –  DoME

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