Six enormous coke drums at the Chevron El Segundo Refinery, which produces 20 percent of Southern California’s vehicle fuel, were showing their age after 46 years in service. Nearly five decades of high-pressure/high-heat cycles that thermally crack crude oil molecules into petroleum products were also cracking the coke drum shells. This cracking posed a significant challenge to their safe removal and replacement in a $55 million turnaround completed in June 2014. Everyone involved in the project credits extensive planning by experienced contractors, continuous top-to-bottom communication, and innovative problem solving for making the project one Chevron calls ‘World Class’.
“Our approach was to hire the best we could get, because the job was going to be high risk. Clearly we wanted nobody to get seriously hurt because any potential incident on a structure like this could be fatal,” said Rick Miller, Chevron Coke Drum Reliability Project Manager. “So we decided to sole source to Nooter, who arguably along with their sister company Wyatt are the premiere coke drum replacement contractors.”
The El Segundo coke drums had come full circle for Nooter Construction, the St. Louis Company that installed them in 1968. Nooter has a long history of coke drum turnarounds, specializing in removing the cutting deck and derricks from the top of the Coker unit to allow one-piece drum removal and replacement.
“Using this method to remove and replace a completed coke drum on average takes about a day to perform. This compares to a period of approximately one month per drum if the vessels were removed and replaced in sections,” said Ed Collins, Nooter Construction Senior Rigging Engineer. “If the benefit of expediting a project versus the cost to expedite results is a ratio greater than one, it solidifies our position to perform the high risk one piece structure lift operation. We have typically found owners agreeable to this approach.”
The crane required two months just to set up but was capable of moving the six derrick structure and cutting deck in one piece without twisting or distorting the shape.
The planning paid off during a key decision involving the method to remove the old coke drums. Normally, lifting lugs are welded onto opposite sides of each drum so slings can be attached to lift the drums out. However concerns emerged that the required welding would extend the turnaround time and that the stress on the lifting lugs could cause unnoticed cracks on the 46 year old vessels to open.
“From the standpoint of constructability and usability, every component of the design worked exactly as intended,” Collins said.
“That saved a huge amount of time and was a very technically savvy way to do it. It looked a little bit old school compared to welding on big fancy lifting lugs. But it worked perfectly,” Miller said.