Black steel is an uncoated steel also called black iron. The name is derived from the black oxide scale that forms on the surface during the forging process. It is coated with protective oil to prevent rust and corrosion after forging. This steel is used to manufacture piping and tubing and is preferred for many projects due to the low maintenance required.
Black steel pipe strength makes it ideal for transporting water, gas, high pressure steam and air in both rural and urban areas. It is also used to protect electrical wiring. The oil and petroleum industries use this pipe for moving large quanitities of oil as it has proven effective in long-term use situations. This pipe is never used for transporting potable water as the oil coating used to prevent corrosion is toxic if ingested.
Black steel pipe and tubing made of this material is cut and threaded to fit the job. Fittings for this type of pipe are made of black, malleable cast iron connected by screwing the connecting pieces onto the threaded pipe after the application of a small amount of pipe joint compound. Larger diameter black steel pipe is welded rather than threaded and can be cut with a heavy-duty tube cutter, cut-off saw or hacksaw.
There are two types of standards for black steel pipe: Indian and British. The Indian Standards utilise specification IS: 1239-1900, 1978-1982, 1161-1998, 3601-1984, and 3589-1991. These standards specify that the material must be black, galvanised, and have a plain end that can be screwed or socketed. The standards also cover steel thicknesses from 150 to 400 millimetres. The British Standards for black steel pipe can be found in specification BS: 1387-1985 and 1775-1964, which covers steel tubes for mechanical, structural and general engineering purposes.
Modern technology has provided manufacturers with the ability to accurately measure black steel pipe for both efficiency and quality-control performance standards. Testing methods include special x-ray gauges to ensure a uniform wall thickness. The pipe strength can be tested with water under high pressure to ensure durability. All black steel pipe that does not meet efficiency, quality, thickness and durability tests are prohibited from entering the market and are generally recycled for re-manufacturing processes.
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