1999 Ford Windstar Power Steering Pumps

I have replaced the power steering pump on my Windstar atleast 4 different times in the last 6 months. I have also replaced the rack-n-pinion part of the steering too. The pump just went bad again. It will be going fine,then it just quits. Could there be something in the power steering fluid that is killing the pumps or just a bad batch of pumps.

How are you testing the pumps to know they are bad? How did the first pump fail? Did you flush the system before installing the first replacement pump? If not, you could have trapped a lot of metal debris which could keep circulating and clogging or jamming the system.