Engineering consultants have concluded that the closed facilities of the Youngstown Sheet and Tube Co. in Campbell, Ohio, could be reopened gradually starting next fall, helping to restore the economic health of a region newly depressed by steel plant closings.

Under new ownership and management, the steel producing complex could grow to an annual volume of business estimated at $802 million by 1985 and could begin earning a profit by the early 1980s, according to a study to be made public today.

A capital investment of $535 million would be necessary to launch the new venture, of which about 40 per cent must be raised during the next two years, consulting engineer George R. Beetle has concluded.

About 2,000 currently idle steel workers could be re-employed by the end of 1979 and between 3,500 and 5,000 steel jobs would be created over a longer term in the Mahoning Valley region of Ohio, where the Youngstown plant is located, Beetle asserts.

Today, about 4,800 former steel workers are searching for jobs in the wake of a decision on Sept. 22 to close facilities that produced flat rolled, bar and welded pipe products at the aging Campbell Works and to reduce production of seamless pipe and tubing at Brier Hill, both near Youngstown.

Lykes Corpl., the parent company of Youngstown Sheet Tube, said it no longer could support unprofitable operations in the Ohio industrial center, where initial iron production started in 1803.

Beetle, a Philadelphia consultant, prepared his analysis for the Western Reserve Economic Development Agency, which is supported by 20 local governments in the Youngstown area. His study is scheduled for release at at news conference at Youngstown State University this morning.

Although Beetle concludes that a gradual reopening and construction of new facilities for more efficient production is feasible, his report does not propose a structure for new ownership.

A separate organization, the Washington-based Exploratory Project for Economic Alternatives, is drawing up a proposal for combined worker-community ownership for submission to the Ohio agency.

Although Beetle said "serious difficulties" will face new management at the Youngstown facilities, he concludes that "prospects for long-term success are good," especially if steel prices are permitted to rise, eliminating a situation in Youngstown where revenues for produced steel have been as much as 30 per cent below list prices.

He recommended a staged reopening of various facilities but warned that necessary organizational and financing work must be completed in a relatively short period of nine months.

Beetle says several possibilities exist for public financial support of the plant acquisition and reopening - county bonding authority for pollution control equipment, for one. In addition, Youngstown area spokesmen are confident the federal government might aid such a project with loan guarantees if plant modernization is included.