black carbon steel pipeSteel with a surface layer of dark coloured iron oxides used for low pressure hot water heating pipes.

How about also adding steam, steam condensate, air, natual gas, oil 1, 2,3,5, and bunker C besides hydronics and HVAC systems such chilled water and who would leave out fire suppression piping Also DO NOT beliewve the lies the other poster wrote as Black Iron can be used on high presure steam (15# and above ) .

As even a helper or someone with very little knowledge would know that black steel comes in a variety of schedules (wall thicknesses) so 40 is standard up to 125 PSI .

Schedule 80 and schedule 120 so the thicker the wall the higher the pressure it can convey Ships use 1,500 PSI Superr heated piping ALL black steel .

Black steel pipes have the strength that can make it ideal for transporting water and gas in rural and urban areas and for conduits that protect electrical wiring and for delivering high pressure steam and air. 

The oil and petroleum industries use black steel pipe for moving large quantities of oil through remote areas.

 This is beneficial, since black steel pipes require very little maintenance. Other uses for black steel pipes include gas distribution inside and outside homes.

water wells and sewage systems. Black steel pipes are never used for transporting potable water.