Essar Oil Ltd., controlled by billionaire brothers Shashikant and Ravikant Ruia, will shut its refinery on India’s western coast for 30 days for maintenance, the plant’s first major break in four years.

The nation’s second-largest non-state refinery, which has an annual capacity of 20 million metric tons, will close on Sept. 18, according to an exchange filing. Maintenance work will be completed by Oct. 17.

A four-week shutdown of the plant, located at Vadinar in Gujarat state, had to be deferred from May-June so that Essar Oil could tap higher refining margins amid rising demand and falling crude prices. There will be no output from the plant, Essar Oil’s only refinery, during the shutdown.

Shares of the Mumbai-based company fell 0.7 percent to 183.85 rupees at the close in Mumbai Wednesday. The stock has gained 72 percent this year, compared with a 5.6 percent drop in the benchmark S&P BSE Sensex.

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