NEW YORK May 24 (Reuters) - Two oil companies that ship crude oil on Enbridge Energy Partners LP's North Dakota pipeline system filed motions with federal energy regulators this week over their concerns about Enbridge's proposal to limit the amount of potentially deadly gas in crude oil shipped on the line.
Restrictions on sulfide gas limits in crude would put a crimp in the business operations of companies that ship oil on the line, Marathon Petroleum Corp and Murex Petroleum Corp said in the motions.
On May 8, Enbridge had filed a request with the U.S. Federal Energy Regulatory Commission (FERC) to restrict the amount of hydrogen sulfide gas in crude shipped on its pipeline as soon as the next day, citing concerns about the safety of its employees handling the crude.
The request was filed three days after Enbridge found dangerous amounts of sulfide gas in one of its storage tanks at its Berthold, North Dakota, rail terminal that ships oil out of the Bakken shale. The company threatened to shut the 80,000 barrel-per-day terminal if it could not limit the amount of sulfide gas shipped on the line.
Marathon filed on Wednesday a so-called motion to intervene in Enbridge's request to FERC, saying the new hydrogen sulfide specification could adversely affect its crude oil suppliers.
Marathon ships crude to its refineries on Enbridge's line.
Murex Petroleum Corp had a stronger objection in its filing late on Thursday, saying that before setting guidelines Enbridge should explain how so much sulfide gas was in one of its tanks.
On May 15, Hess Corp filed a standard motion to intervene in the proceeding. Plains Marketing, a unit of Plains All American Pipeline, filed an objection to Enbridge's request two weeks ago.
In small doses, hydrogen sulfide will irritate eyes, nose and throat. But the company said it found 1,200 ppm (parts per million) in one of its tanks.
"Exposure at 50 ppm or above could cause shock, convulsions, coma or death," Enbridge said in a May 14 filing in response to Plains, noting that at levels above 200 ppm, "respiratory failure can occur within seconds after only a few inhalations."
Enbridge sought to limit to 5 ppm the amount of sulfide gas in the crude.
Last week Enbridge said it would accept crude oil containing high levels of sulfide gas with advance notice, if it can safely accommodate the oil.
The company also said should it receive crude with sulfide gas levels of greater than 5 ppm without its prior approval, it "reserves the right to shut down such injection facility and may seek reimbursement for any damages caused by the unauthorized delivery."
FERC is expected to make a decision on Enbridge's request on June 7.