French to English Tech/Engineering Energy / Power Generation Power station

From a set of flow calculations for a power plant:

Débit d'eau de bourrage des pompes alimentaires
- aller TP A1
- aller TP A2
- aller MP A
Débit total "aller" (=A)
- retour TP A1
- retour TP A2
- retour MP A
- débit total "retour" (=B)
Débit d'eau de fuites aux bourrages des 3 pompes vers bac des purges (=C)

I have no idea how to translate "bourrage" here - normally I would have thought it was "packing", but I can't see how that fits in.

Any suggestions/explanations very gratefully received, as ever...