How to fill a pipeline

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Canada's latest pipeline is open for business, providing oil sands producers with another major outlet for their crude.

Enbridge Inc. late last week launched the Alberta Clipper line, capable of delivering 450,000 barrels per day to the refinery hub in the U.S. Midwest - and as much as 800,000 barrels per day if the company were to expand it in the future.

Filling the Clipper pipeline took six million barrels of oil - creating worry among analysts that the extra demand could nudge up oil prices.

The pipe has been mechanically ready since April. But pressing a $3.1-billion pipeline into service isn't as simple as opening valves and letting the crude gush. It is a complicated, months-long operation that slowly fills the empty void with a volatile substance, a dangerous activity if not done carefully.

Once regulators sign off on the safety of a pipeline, "we're basically sitting there with hundreds or thousands of miles of pipe that's basically empty and effectively full of air," said John Glanzer, Enbridge's director of shipping services.

"Of course, since we're running a hydrocarbon in the pipe, one thing we want to avoid is mixing the hydrocarbon with the air," which is a combustion risk, he said.

FROM EMPTY TO FLOWING

1. Workers inject nitrogen into the head of the pipeline. Nitrogen is inert; it won't allow oil to combust, as oxygen might.

2. Enough nitrogen is used to create an oxygen-free "blanket" up to 150 kilometres long.

3. Workers install a batch or separation "pig," a unit that travels down the inside of the pipe with rubber cups on the sides, to prevent contact between the nitrogen and the oil. (Think of the rubber plunger in a syringe.)

4. About 1.5 km worth of pipe is filled with oil.

5. A second separation pig is installed. This is done to make doubly certain that nitrogen doesn't contaminate the oil - even the first dribbles of oil belong to energy companies, and the intent is to ensure that every bit of crude is a marketable product.

6. The company begins to pump larger volumes of oil, filling the first section of pipe. Sections can be dozens of kilometres long and are separated from each other by valves.

7. Special startup crews walk and drive along the line to monitor the pigs' progress, ensuring the company knows exactly where they are at all times. They track the pigs using radio transmitters, but the pigs are also designed with "rattlers" that make enough noise they can be tracked by ear.

8. Maintenance crews open the valves to new sections as oil reaches them, being careful to maintain the nitrogen blanket.

9. Pipelines operate with minimum flow rates, which means a high volume of crude needs to be pumped to keep the line-fill going. To lessen the market impact of sucking so much crude into the line, it is pumped several hours at a time, then paused for several hours.

10. When the nitrogen blanket reaches the end of the line, crews conduct a "blowdown" procedure. The nitrogen is scrubbed of hydrocarbons and vented to the atmosphere.

11. The line is ready to deliver crude.