A House Interior subcommittee voted yesterday to delay for another six months any consideration of controversial coal slurry pipeline legislation.

The legislation is strongly opposed by railway unions and railroads, which currently carry about two-thirds of the country's coal and hope to gain a badly needed financial injection from increased use of coal.

Sponsored by Rep. Bob Eckhardt (D-Tex.), the bill would give pipeline companies authority to seek powers of eminent domain. The railroads have threatened to block the pipelines from crossing under their tracks.

The delay was approved 13-12 with six Democrats and seven Republicans in the majority. The bill is now scheduled for consideration after next Jan. 1.

Under the slurry process, roughly equal amounts of water and pulverized coal are pumped through the pipeline. Several utility consortia have planned pipelines from strip mines in Wyoming and Colorado to generating plants in Texas and from Montana to the Northwest.

Eckhardt yesterday blamed the delay on "massive lobbying by the railroads."

Those favoring the delay claimed they were waiting to see the results of a long overdue study on the slurry process by the congressional Office of Technology Assessment. The main issue is the effect on the mining states of losing the vast quantities of water that must be used with the coal.

But coal Slurry Association President Pat Jennings complained: "I can't understand a study of the technology when the same technology is used in this country and abroad."

Richard Briggs, vice president for public affairs at the Association of American Railroads, said that his organization and the Railway Labor Executives Association teamed up against the bill.

"For the marginal railroads out there that are counting on coal hauling to survive, this comes as a great relief," he said.

The Carter administration has verbally backed the bill, but Eckhardt complained that the lack of a firm written commitment from the administration was partly the cause of yesterday's setback.

Several Democrats spoke for the bill before the vote was taken.

They said that slurry pipelines are crucial to the administration's plans to use more coal and to lessen the country's dependency on oil and natural gas.

However, at least one Republican whose state has water projects on the administration's so-called "hit list" to be abandoned, was heard to say he voted against the slurry measure in retaliation.

One opponent of the pipelines, Rep. Teno Roncalio (D-Wyo.), claimed that they would use so much water that the water table would be lowered, threatening crops in Wyoming, Nebraska and South Dakota.

An aide to Eckhardt said last night the bill's backers were weighing a motion to reconsider yesterday's vote.