When plumbing a fluid system, selecting the proper fittings to connect the piping is crucial. Factors like material, sealing method, pressure rating, and compliance with standards should guide the decision process. Learn more below about common options like stainless threaded fittings, carbon steel press fittings, and more.
ASTM A403 Stainless Steel Pipe Fittings Threaded
For a versatile, high-performance fitting material, stainless steel is a top choice. Stainless steel fittings like elbows, tees and couplings conforming to ASTM A403 withstand high pressures and resist corrosion.
The 300 series stainless alloys used, most often 304 or 316, provide strength and excellent chemical resistance. The smooth forged fitting interiors maintain flow and avoid contamination points.
A403 fittings contain tapered NPT pipe threads. PTFE thread sealant tape creates tight leak-free joints. Stainless steel’s rust resistance prevents seizing or deterioration of the threads over time.
Thanks to stainless steel’s durability, A403 threaded fittings can outlast the service life of carbon steel alternatives. Their ability to withstand high temperatures and pressures makes stainless fittings suitable for demanding applications like hydraulic systems.
Carbon Steel Press Fittings
Press fittings provide fast, secure pipe joining without threads or soldering. The fittings use O-ring seals and mechanical deformation to create joints. Carbon steel press fittings offer an economical alternative to stainless press fittings.
To install, simply insert the pipe end fully into the press fitting. Special pressing tools radially compress the fitting interior. This forms a tight all-around seal between the fitting and pipe.
Carbon steel press fittings are available in sizes up to 4 inches diameter. Their compactsingle-piece design eliminates loose parts or leaks between connections. No special skills required.
However, check system temperatures and fluids against the press fitting manufacturer’s ratings. Carbon steel has lower corrosion resistance compared to stainless. Only use fittings approved for the application.
Pipe Threaded Seal
Threaded fittings rely on tapered pipe threads to form a tight friction seal. However, preventing leaks requires additional sealant applied to the threads. Three common types suitable for stainless and carbon steel threaded pipe fittings include:
- PTFE tape – Creates a non-stick barrier while filling voids between threads. Best for low pressures.
- Pipe dope – Applied like grease, it lubricates and seals threads. Ideal for high pressures and temperatures.
- Anaerobic threadlockers – Hardens between threads once assembled. Locks and seals while preventing vibration looseness.
Apply the sealant according to manufacturer directions to ensure proper setup and performance. This completes the leak-free threaded connection.