Transfer Pumping
So-called transfer pumping is required since two reservoirs are used for storing the urea-water solution. The term transfer pumping relates to pumping the urea-water solution from the passive reservoir into the active reservoir.
| Index | Explanation |
|---|---|
| 1 | Passive reservoir |
| 2 | Level sensors |
| 3 | Extractor connections |
| 4 | Transfer line |
| 5 | Filter |
| 6 | Pump |
| 7 | Non-return valve |
| 8 | Level sensor |
| 9 | Active reservoir |
The following conditions must be met for transfer pumping:
- There is a urea-water solution in the passive reservoir
- The ambient temperature is above a minimum value of -5°C for at least 10 minutes
- A defined quantity (300 ml) was used up in the active reservoir or the reserve level in the active reservoir was reached.
The solution is then pumped for a certain time in order to refill the active reservoir. The transfer pumping procedure is terminated if the "full" level is reached before the time has elapsed.
If the passive reservoir was refilled, transfer pumping will only take place after a quantity of approximately 3 liters has been used up in the active reservoir. The entire quantity is then pumped over.
The system then waits again until a quantity of approximately 3 liters has been used up in the active reservoir before again pumping the entire quantity while simultaneously starting the incorrect refilling detection function.
This function determines whether the system has been filled with the wrong medium as it is present in high concentration in the active reservoir.
Transfer pumping does not take place in the event of a fault in the level sensor system.