I’m not sure how accurate this info from the modder is but this is how he describes it under his mod:

Experienced players can predict that the pipes will always malfunction 2 or 3 times, first time around 35%, second time around 70%, and maybe a third time after 90%. Generally, it’s every 50-70 seconds (average of 60 seconds).

This simple mod shakes things up by randomizing when the pipes will break - while still maintaining the same average time between breakdowns. Now pipes can jam anywhere from 5 to 115 seconds between breakdowns (average of 60 seconds). So you never know what you’re gonna get!

Mod: https://mod.io/g/drg/m/random-refinery-breakdowns

This is the only instance of it being described that I’m aware of because I was looking up refinery mods in the past. I tried looking up this info on the web to answer your question with more credible sources but I didn’t find any and didn’t bother spending too much time on that.