Corrosion because a valved leaked caustic into a relatively new crude unit that was off line for some quick repairs will cause the unit to be down for perhaps a year. Here’s the story:

http://in.reuters.com/article/2012/07/16/refinery-operations-motiva-portarthur-idINL2E8IBEFL20120716

Human error? Equipment failure? Bad operating or maintenance practices? Unexpected corrosion? Non of these are root causes. To find the root causes you need a systematic process like Equifactor® and TapRooT® to troubleshoot equipment problems and dig down to the real, fixable root causes of the problems. 

For more information about TapRooT®, see:

http://www.taproot.com/products-services/about-taproot