Vectren Corp. is accelerating its 20-year program to replace older steel and iron gas lines to home and businesses throughout the region, the natural gas supplier said Friday.

Vectren’s work is happening now largely in Dayton, but crews have worked on 36 projects this year, said spokeswoman Chase Kelley. The utility set a new goal of replacing up to 55 miles a year, compared with 30 to 40 miles in previous years, to complete the project by 2020-24.

The work follows the federal Pipeline Safety Improvement Act of 2002, which mandated tougher pipeline safety standards.

Duke Energy is also replacing gas mains and service lines, as are utilities in all 50 states. Duke’s 15 -year improvement project began in 2001 to enhance safety and reliability of the system, Duke spokeswoman Sally Thelen said.

Duke’s program wrapped up in Northern Kentucky at the end of 2010 and is scheduled to be completed in Ohio by the end of 2015. Nearly 1,200 miles will be replaced.

Vectren has more than 5,500 miles of lines and mains in its 17-county Ohio service territory. The program will replace more than 1,700 miles of aging bare steel and cast iron pipeline throughout service territories in Indiana and Ohio, with 700 miles in Ohio. Kelley said the work supports up to 425 jobs per year, 255 direct and 170 indirect. In Ohio, 120 miles have been completed.

Lines and mains are replaced with polyethylene or plastic lines engineered to carry natural gas. Homes and businesses with gas meters indoors are getting new gas meters on the outside of the structures. Some meters are equipped to be read remotely.

Crews have worked Riverside, Miamisburg, Piqua, Xenia, Bellefontaine, Sidney, Troy, Jamestown, Washington Courthouse, Cedarville, Bradford, Greenville, and Eaton, but most of the resources are in Dayton. Older infrastructure is the target, Kelley said, not newer suburbs with modern lines.