I've not worked in a HDPE manufacturing plant, but I can imagine that this had to be tough to deal with: Chevron Loses Power at Pasadena, Texas, Chemical Plant.
My first job was located at a PP film plant in Terre Haute, Indiana. A small group of us were part of the corporate R & D structure, but were located at a manufacturing site to get exposure to the function. To further drive home that we did not work for the manufacturing plant, we had offices in a double-wide trailer (yes, I was trailer trash for a year). These high end accommodations were located just outside the tower where the blown PP film was made. One hot summer day there was a dip in the power, just enough to blacken the computer monitors but not enough to reboot them. A second or two later, we heard the "gunshots": BOOM, BOOM, BOOM, BOOM, BOOM, BOOM. All six bubbles had popped.
A colleague said to stay put, but being naive and innocent, I went anyway. What a mess. I just started grabbing film and pulling it to the garbage. I don't recall how many hours it took to clean everything and then get all 6 lines restarted, all because of a 1-second dip.
I can't imagine the problems that could occur in a large manufacturing site with a total outage. Certainly the plant is designed to safely shutdown (failsafe), but the restart would be the bigger concern.