GDANSK: There is a risk that Russian oil flows to Poland might be temporarily suspended again due to excessive levels of organic chloride, the chief executive of Polish pipeline operator PERN said on Tuesday.

Poland halted Russian oil imports via Druzhba pipeline in April after the discovery of excessive levels of organic chloride, which can damage refinery equipment.

Flows partially resumed in June, but were suspended temporarily again on June 19 after excessive organic chloride levels were again detected.

"I would really like it not to be the case, but... there will always be remaining oil which could have higher chloride content," CEO Igor Wasilewski told reporters at PERN's crude oil shipment terminal in Gdansk, on the Baltic Sea.

He said PERN is checking the Russian oil for quality and taking samples every three hours compared to every 10 days before crisis.

PERN's clients include two Polish refineries - one in Gdansk owned by Lotos and one in Plock controlled by PKN Orlen - plus two plants in Germany. The Polish refiners used sea-borne supplies and oil inventories to keep their plants working when deliveries from Russia were suspended.

Wasilewski said cleaning up contamination of the Polish pipeline system is expected to take 6-8 months.

"How long the situation lasts depends on how the refineries work," he said. "There has not been a situation like this for 50 years and all the refineries are learning as they go along."

As a result of the Druzhba pipeline crisis Poland imported 2.2 million tonnes of crude oil by sea through the Naftoport terminal in May, more than twice as much as in May the previous year, PERN said.

The Naftoport terminal consists of 5 universal transhipment stations, where the largest tankers on the Baltic Sea are operated.

Wasilewski said the crisis caused by the Druzhba pipeline shutdown showed how important it is for Poland to build a second section of pipeline linking Plock and Gdansk so that the Plock refinery can take more sea-borne supplies in future.