The trans-Alaska pipeline -- the spine of the state's oil-dependent economy -- is back on the job this week after a series of expensive and disruptive emergency shutdowns.

But now is not the time to celebrate, the pipeline operator and regulators said Tuesday.

Like a patient recovering from surgery, the pipeline is still in critical condition.

In fact, the potential remains for another major shutdown in the dead of winter.

The main concern is the temperature of oil in the pipeline. At some locations, the oil temperature is well below freezing, and Alyeska Pipeline Service Co. needs to get bring it back to normal or risk major damage to the 800-mile line.

Also, the pipeline system has lines at other locations that might be similar to the leaky one on the North Slope that triggered the shutdowns starting Jan. 8. Alyeska's newly minted chief executive, Tom Barrett, said Tuesday he has ordered an inventory of the other lines. If needed, the company will take immediate steps to deal with them, he said.

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