Normalmente, corrían 1500 litros de petróleo por las cañerías, pero una vez, en 1985, a causa de un desperfecto, corrieron 3000 litros de petróleo (por las cañerías) hasta que se solucionó el problema.
usually flow-impf liters of petroleum through the pipes but one time in due to a malfunction flow-pret liters of petroleum through the pipes until solve-pret the problem
Usually, 1500 liters of oil flowed/were flowing through the pipes. But once, in 1985, due to some malfunction, 3000 liters were flowing (through the pipes) until the problem was solved.