The company will shut its No 3 CDU unit from Oct. 21 to Nov. 15, spokesman KY Lin said.
The No. 2 RDS unit will be offline from Oct. 11 to Nov. 16, he added.
The company has a crude processing capacity of 540,000 barrels per day.
(Reporting by Trixie Sher Li Yap; editing by Jason Neely)