In the field of piping materials, black steel pipes are used by steamfitters, plumbers and other mechanical contractors for pressurized flow of liquids or gases. Black steel pipes and fittings are constructed of steel that hasn't had a finish applied to it, while zinc-coated galvanized fittings possess very good corrosion resistance and strength.
Black iron piping, also known as schedule 40 steel or schedule 40 black pipe, is frequently used in fire sprinkler systems and gas transportation, because they are more resistant to heat than schedule 40 galvanized pipes. Schedule 40 is the most frequently used pipe schedule by mechanical contractors. Their fittings connect low to medium pressure piping systems, where black iron adapters are often found on the return (low pressure) side of gas or liquid transfer lines and hydraulic systems.
Malleable iron is made by a casting method. Although malleable iron fittings begin as cast iron, they are altered by heat to increase their durability and strength. Class 300 malleable iron fittings can handle pressures of up to 300 psi and more demanding applications than class 150 fittings, which are rated to 150 psi. However, you must consider temperature in material type selection as the pressure of each style is correlated to temperature.
Application criteria
Black and galvanized steel piping are the most commonly used to convey liquid and gas in construction, some hydraulic and many industrial piping systems. Although both galvanized and black steel pipes are formed of steel, the former has a zinc coating, while the latter does not.
Black steel pipe is frequently used in hydraulic applications from construction to robotics, while galvanized pipe should not be used in hydraulic systems. This is because galvanized material may peel off into the system, causing fluid contamination. Due to the fact black steel piping is seamless, it is used to transport gas in commercial buildings. Black steel piping is also ideal for fire sprinkler systems because of its fireproof characteristics.
Weldability of black malleable iron fittings
One of the benefits of black malleable iron pipe is weldability for many applications, using TIG, MIG, stick arc and flux core arc welding. The malleable nature of the iron allows the material to be welded without becoming brittle or cracked. Conversely, malleable black iron fittings are difficult to weld and may cause damage to the fitting and joint. Even though they are weldable, you should not weld a malleable iron pipe fitting that is in a pressurized system because welding alters the material’s structural integrity. Ideally, brazing is typically more suitable for joining these fittings to pipe.
The construction industry
Black malleable iron pipe and fittings are popular in the construction industry since the material's strength allows the fittings to withstand harsh conditions. This makes the material well suited for critical systems like fire suppression, where reliability is paramount. Its long service life also lowers the total cost of ownership over the system's lifetime, making it essential across many construction segments.
Conclusion
Black malleable iron fittings play an important role in construction and industrial applications. These fittings offer superior strength and weldability under the right conditions. Their unique properties provide durability, flexibility and reliability that benefit many applications. Ongoing material science and manufacturing advances may unlock even greater potential from malleable iron. Contractors, engineers and architects will continue to rely on the capabilities of these fittings for many applications. As costs decrease, black malleable iron can become an increasingly standard component of high-quality, resilient applications in many industries.
Black iron pipe has been around for over 300 years. Today, with ongoing advancements and the potential of new applications, the possibility to enhance the strength and workability of these fittings could further broaden their capabilities. The low cost and ease of use black malleable iron piping and fittings will solidify their place in building and hydraulic applications.
Sources: