Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If working in this factory requires that the tools used for slaughtering pigs be washed, and it is not possible for the worker to avoid that, and limit himself to just washing the tools used to slaughter other animals like sheep and animals that we are allowed to eat, then it is not allowed to work in this factory.
Working in such a factory is helping in sin and mischief. Allah forbade that by Saying: {…but do not help one another in sin and transgression….}[5:2].
Allah knows best.