RE:RE:RE::-)
they are not pressure relief valves. Not trying to be rude, but the article states they are 3 inch ball valves that can leak crude if the plugs cause damage. Just google ball valve and you will see these are valves meant for opening and closing. The plug is an added measure to prevent leaks in addition to the closed valve. You wouldn't want to thread a plug on a pressure relief valve. Lots of good info on this board, and I just wanted to make this clarification so we don't get to excited over this article.