Pump module, component description

W14.40-1208-06

Arrangement

18 Pump module

The pump module (18) is located at the right side of the chassis frame at the height of the AdBlue reservoir.

Task

The pump module (18) draws AdBlue from the AdBlue reservoir, filters it and pumps it to the metering unit.

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Composition

1 Pressure filter

2 AdBlue pipe - supply

3 AdBlue pipe - return

4 Pneumatic control pipe

5 Compressed air connection

6 Pressure accumulator

7 Housing of the filter and of the pressure accumulator

8 Coolant pipe - outlet (not utilized in Brazil)

9 Accumulator charging valve

10 Accumulator charging connection

11 Coolant pipe - inlet (not utilized in Brazil)

12 Pump housing

13 Housing cover

14 Electric connection

15 Cover of the ventilation membrane

16 AdBlue pipe - suction

17 Intake filter

M25 AdBlue pump

W14.40-1031-12

The pump module comprises a synthetic material case - the pump housing (12) is aluminum made and is attached to the filter and pressure accumulator housing (7). In the pump housing (12) is the AdBlue pump (M25) - an electric diaphragm pump with 3 chambers.

In the filter and pressure accumulator housing (7) is, beside the pressure filter (1) and beside the pressure accumulator (6), a pneumatic control valve (4).

Operation

When the AdBlue pump (M25) receives the actuation signal, it draws AdBlue from the reservoir. AdBlue is pre-filtered by the suction filter (7), of 100 µm mesh, integrated in the AdBlue suction pipe.

The pump pressurizes AdBlue to an operational pressure of about 6 bar and conducts it to the filter and pressure accumulator housing (7). To eliminate minor dirt particles, AdBlue passes through the pressure filter (1), with 30 µm mesh, before being pumped to the metering unit.

The pressure accumulator (6) is basically a rubber made bladder full of gas, whose function is to compensate pressure oscillations and to reduce the AdBlue pump (M25) kick-in frequency. It has approximate volume of 0.13 l and it is charged with nitrogen (N2) ex-factory. When recharging, the accumulator can be charged with air free of oil or grease.

Ventilation

The pneumatic control valve (4) and the AdBlue pipe neck (3) are for the automatic ventilation of the pump module during operation or when putting into operation. The pneumatic control valve (4) remains shut when submitted to compressed air pressure.

usually, the AdBlue pump (M25) does not operate when "empty", as it switches off when the level sensor in the AdBlue reservoir gets below a certain limit value. In the case the AdBlue level in the reservoir gets low for brief moments in function of vehicle rocking and, consequently, the reservoir and the AdBlue inside it, the pump will work empty for a short period of time. If the AdBlue pump (M25) runs empty for more than 10 seconds, this will be recognized by the engine control module (MR) and the automatic ventilation will be initiated.

AdBlue pressure reduction

To avoid that freezing AdBlue damages the pump module, the AdBlue pressure is reduced inside the pump module and in the pipe stretch between the pump module and the metering apparatus, after ignition disconnection. The pressure reduction occurs simultaneously with the ventilation of the compressed air control module. This way, the pneumatic control valve (4) is opened, enabling the AdBlue return to the AdBlue reservoir.