Qingdao and Lanshan are two of the top five biggest Chinese oil importing ports, according to data from Kpler. Shandong is home to numerous independent refineries known as teapots that account for up to one-fifth of China's processing capacity. Port authorities could detain ships for days to rectify any issues, prompting shippers to divert cargoes to other Chinese ports, the sources said. Almost all tankers hauling crude to Qingdao for independent refiners are more than 10 years old, said Vortexa analyst Emma Li. In April, tankers calling at Shandong ports experienced delays after customs authorities stepped up checks on diluted bitumen cargoes.

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Persons: Seapalm, Emma Li, Eikon, Muyu Xu, Florence Tan Organizations: Kpler, Shandong Maritime Safety Administration, Reuters, Seapalm Shipping, Thomson Locations: SINGAPORE, China's Shandong, Qingdao, Rizhao, Lanshan, Shandong, Tokyo, Cameroon, Seychelles, Jiangsu, Hebei, Liaoning, Beijing