SEAL 5236550 - Caterpillar

The DEF and air are mixed between the fluid cap (5) and a multi-port air nozzle cap (6). The mixed fluid is forced through the multi-port air nozzle cap into the exhaust stream. The compressed air causes the DEF to atomize (separate into tiny particles).DEF Supply Storage System
Two DEF tanks are utilized for the system. A customer supplied tank supplies a buffer tank that is located in the dosing control cabinet. The buffer tank supplies the DEF pump. The buffer tank is equipped with a level sensor and a temperature sensor.Note: The customer is responsible for providing primary filtering of the DEF from the site tank to the buffer tank. The system requires a 40 micron primary filter.DEF must be provided from the site tank to the dosing cabinet between 34 kPa (5 psi) and 69 kPa (10 psi) head pressure. If pressure is not achievable based on relative location of the dosing cabinet and the site DEF tank, a DEF boost pump may be required.Pins are available on the dosing cabinet connector to activate the DEF transfer pump when DEF is being drawn out of the main tank. If pressure is too high, the buffer tank may overfill.DEF flow will vary with engine operating conditions, specifically with load. The DEF flow requirement is calculated as a percentage of fuel flow.The fill and refill of the buffer tank is automatic and controlled by ECM software as long as DEF pressure at the DEF supply port is 2-3 psig with a max of 5 psig during the fill and refill process.CEM Identification Number Module
The identification number module outputs a 10 character alphanumeric serial number for the CEM to the SCR system ECM.The SCR system ECM transmits this data to the engine ECM over the local CAN data link.The engine ECM compares the first 3 letters of the serial number (the prefix) to a value programmed into the engine software.Sensors (CEM)
NOx Sensors
The NOx sensor communicates to the SCR system ECM over the CAN data link. The sensor has built-in diagnostics to indicate sensor failure modes.The SCR system ECM controls the power supply to the NOx sensors.Aftertreatment #1 Intake NOx Sensor
The aftertreatment #1 intake NOx sensor is monitored to control the DEF dosing rate based on engine out emissions levels.Aftertreatment #1 Outlet NOx Sensor
The aftertreatment #1 outlet NOx sensor is monitored to control the DEF dosing rate based on catalyst out emissions. The SCR system ECM monitors the sensor to calculate the necessary DEF flow rate to meet emission targets.Temperature Sensors
Aftertreatment #1 SCR Catalyst Intake Gas Temperature Sensor
The aftertreatment #1 SCR catalyst intake gas temperature sensor is monitored for dosing control and system protection.The temperature indicates the capability