The owners of a 22-mile oil pipeline that experienced a testing blowout under the Long Island Expressway two years ago are asking the state to "lighten" rules on future tests as they seek to convert it to transmit natural gas.

In documents filed with state and federal regulators, lawyers for Northville Industries said the pipeline, which is not in use, would serve 19 "large, commercially sophisticated" customers for gas throughout Long Island.

The 16-inch steel pipeline runs from Holtsville, where Northville operates a large storage tank facility, to Plainview. Company officials said the plan would be to run "laterals," or connecting distribution pipelines, from the main line to supply customers. It could ultimately provide gas for National Grid or other power plants, they said.

"We're recycling a very valuable asset," Northville chairman Gene Bernstein said. "There's a shortage of natural gas on Long Island. This will help to get more gas to potential customers."

The pipeline and the plan to convert it made news in 2013, when Northville was running a water-pressure test to demonstrate that it could handle higher-pressure natural gas.

According to a story in Newsday, "something burst" in the line during the test, scattering debris, flooding the highway with water and damaging six vehicles between Exits 55 and 57 on the Long Island Expressway, which was closed westbound for more than two hours. No one was hurt.

Bernstein said the test was at "significantly higher pressure" than in normal operation, and was intended "to demonstrate a wide margin of safety."

"Northville was testing the pipeline at a pressure more than twice as high as the target maximum operating pressure," he said. "Analysis showed that the pipeline had been previously damaged by a third party at the point of failure. The pipeline was repaired and successfully retested."

Since then, Bernstein said, internal inspections on the line show it is in "excellent condition."

Public Service Commission spokesman James Denn said the Northville filings "will be closely reviewed to ensure that any proposed change, if approved, would be done in a manner that ensures public safety and is in the public interest."

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The petitions will also be subject to public comment, he said.

Bernstein said the conversion plan includes a "comprehensive series of tests, analyses and improvements that will further validate the integrity of the pipeline and enhance its fitness for natural gas service."

In documents filed with the state Public Service Commission and the Federal Energy Regulatory Commission, Northville asked for "lightened" regulation of the pipeline, and a declaratory ruling from the state allowing it to operate at a maximum allowable pressure of 650 pounds per square inch.

Northville wants to bypass a state requirement that 10 percent of the 2,746 lengths of pipeline be randomly tested, requiring 275 separate tests, which the company said "is not practical." That state test would require excavating the pipe, cutting out an 18-inch-long cylinder, welding in a replacement and backfilling the area.

Northville said the hydrostatic pressure test it performed, which conforms to federal rules, "is sufficient to establish maximum allowable operating pressure."

Steve Ripp, director of business development, said the conversion is common.

"Steel pipelines are steel pipelines," he said. "All over the country, lines from one service have been converted to others. There are regulations for performing the conversions."

Northville's state filing said the natural gas business would represent an "extremely small" percentage of its overall revenue and thus was eligible for lightened regulation.

The pipeline, which would be supplied by the Long Island Sound-based Iroquois gas pipeline at its end point in Commack, was listed as one of the alternatives for supplying natural gas to the Caithness II power plant, a 750-megawatt proposal that has been shelved pending a review of regional power sources by PSEG Long Island.