The Billings Phillips 66 refinery is undergoing a complete shut down as it ramps up for major maintenance and improvements that include adding a process to enable it to process more heavy crude oil.

The overhaul, known as a “turnaround,” occurs every five years, takes almost two months and this year, will bring the total number of employees and contractors on site to about 2,500 people during its peak, said Ryan Wegner, the refinery’s finance and public affairs manager, on Wednesday.

Phillips 66 is spending several hundred million dollars on the turnaround, he said.

“We have several cranes, a dozen if not more” on site, Wegner said.

The gradual plant shut down began on April 15, with total shut down by the beginning of May, Wegner said. The refinery will go back online by June. The total turnaround will take about 56 days.

Included in the refinery overhaul is Phillips 66’s Vacuum Improvement Project, which began in 2015, is completed and will be tied into the plant during the turnaround, Wegner said.

The Vacuum Improvement Project will allow the refinery to process more heavy Canadian crude. However, the refinery’s capacity won’t be increased.

The refinery currently processes a mixture of Canadian heavy, high-sulfur crude oil plus domestic high-sulfur and low-sulfur crude oils, all delivered by pipeline and trucks. The project will allow the plant to handle up to 100 percent heavy Canadian crude oil, company officials said earlier.

A major maintenance item will be to make improvements to the refinery’s fluid catalytic cracker, or FCC, which is a processing unit that breaks heavy gas oil into other products like gasoline.

The FCC was installed 68 years ago when the plant was built in 1949, Wegner said. Although regular upkeep has kept the unit running, the company decided it was time for major maintenance, he said.

The normal refinery work force is about 300 workers, but with the turnaround, the numbers of people on site will swell to a high of about 2,500 by the beginning of May, Wegner said. Currently there are about 1,500 employees and contractors on site, he said.

Contractors come from all over the country, including Utah, California and the Gulf states, as well as from Montana, he said.

A concern of Phillips 66 is the safety of the workers and its neighbors, Wegner said. The refinery is working with the city of Billings to address parking, he said. One of the changes will be to have angle parking rather than parallel parking in some areas.

“It allows us to put more cars in the area and less demand on our neighbors,” Wegner said.

Refinery turnarounds typically occur in the spring, before the summer driving season gets started and the demand for fuel increases. Wegner said Phillips 66 prepared for the turnaround with “plenty of inventory” and does not expect local markets to be impacted.

During its last major turnaround in 2012, Phillips 66 installed two 350-ton coker drums. The $48 million project required the assistance of a 1,760-ton crane, which was the world’s fourth-biggest crane. The boom on the crane was 500 feet tall.

The Phillips 66 refinery has a total capacity of 66,000 barrels a day and markets its products in Montana, Wyoming, Idaho, Utah, Colorado and Washington.

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