Classification of Malleable Cast Iron Pipe Fittings

Classification of Malleable Cast Iron Pipe Fittings
Malleable cast iron pipe fittings can be classified in a variety of ways, the most common of which are as follows:
1. Classification by Surface Treatment (Most Commonly Used)
This is the most popular classification method in the market and directly determines the corrosion resistance, appearance, and price of the fittings.
Galvanized Pipe Fittings
Treatment: Hot-dip galvanizing is performed on the fitting surface.
Features: Silvery-white surface with excellent rust and corrosion resistance. Typically used in conjunction with galvanized steel pipes.
Applications: Widely used in piping systems requiring rust resistance, such as building water supply, fire protection, and gas. This is the most common type.
Black Pipe Fittings
Treatment: After casting and cleaning, the fittings are not galvanized and have a black oxide scale or anti-rust paint applied to the surface.
Features: Generally cheaper than galvanized fittings, but with inferior rust resistance.
Applications: Primarily used in applications where corrosion resistance is less critical, or where a secondary coating (such as painting) is required to match the surrounding color. Painted Pipe Fittings
Processing: A layer of rust-proof paint is applied to the cleaned pipe surface.
Features: Rust resistance is between that of black and galvanized steel, and the finish is typically red, blue, or other colors.
Applications: Commonly used for low-pressure fluid transportation or as a marker for differentiating piping systems (e.g., using color to distinguish media).
2. Classification by Thread Standard
This determines the thread specification used to connect the fitting to the pipe.
British Pipe Thread
Standard: Primarily includes the 55° sealing pipe thread, which follows British standards. In China, it is often referred to as “pipe thread” and designated by *G* (e.g., G1/2).
Features*: The thread angle is 55°, and sealing relies on the thread itself (requiring tape or sealant).
Market: This is the most popular and common thread standard for malleable cast iron pipe fittings in the Chinese market.
American Pipe Thread
Standard: Primarily includes the 60° sealing pipe thread, which follows American standards. Designated by *NPT*. Features: Thread angle is 60 degrees with a 1:16 taper, providing enhanced sealing.
Market: Primarily used for products exported to North America and for domestic projects that adhere to American design standards.