JUNEAU -- The operator of the trans-Alaska pipeline plans five shutdowns this summer for maintenance work.

Alyeska Pipeline Service Co. says the shutdowns are expected to last from eight to 18 hours each, with the first planned for Friday.

Alyeska says the maintenance shutdowns are a critical part of ongoing efforts to ensure the integrity of the 800-mile pipeline. They typically coincide with the oil companies' routine maintenance on North Slope equipment and facilities.

Both Friday's shutdown and one scheduled for May 27 are expected to last eight hours. The company expects an 18-hour shutdown on June 2. Alyeska has tentatively scheduled to other shutdowns for July 28 and Aug. 5.