Our church has a buried steam line that serves two buildings. Dec '08 the line failed and was replaced with a fusion bond carbon steel pipe. It has corroded through and must be replaced again. The corrosiion is from the outside. The backfill is sand and pea gravel.
The contractor is proposing to use a DuraBond X-TecTruCoat Schedule 40 pipe with cathode protection via a sacrificial anode.
I suspect the premature failure is either from the wrong type pipe, the wrong type backfill or a combination of the two.