Stainless Pipe vs. Tubing
The terms "Pipe" and "Tubing" are often used interchangeably, but strictly speaking, they refer to different sizing systems. Pipe is measured by Nominal Pipe Size (NPS), while Tubing is measured by exact Outside Diameter (OD).
| Feature | Stainless Pipe (ASTM A312) | Stainless Tubing (A249/A269) |
|---|---|---|
| Measurement | Nominal Pipe Size (NPS) + Schedule | Exact Outside Diameter (OD) + Gauge |
| Example | 2" Sch 40 (Actual OD: 2.375") | 2" Tubing (Actual OD: 2.000") |
| Application | Fluid transport, Industrial Pressure | Stainless Steel Exhaust Pipe, Structural, Ornamental |
Exhaust Pipe Note:
If you are searching for stainless steel exhaust pipe for automotive use, you are likely looking for Tubing, not Pipe. Exhaust systems typically use sizing like "3-inch OD," which matches tubing specs, not the heavy Schedule 40 industrial pipe.
Standard Specs (A312)
ASTM A312 is the standard specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes. This covers the most common grades used in high-temperature and corrosive service.
Grade 304 / 304L
The "workhorse" grade. Excellent corrosion resistance and value. 304L has lower carbon for better welding properties. Used in food processing, chemical, and industrial structures.
Grade 316 / 316L
"Marine Grade." Contains Molybdenum for superior resistance to chlorides and salt water. Essential for marine environments, pharmaceuticals, and coastal handrails.
Stainless Pipe Fittings
A piping system is useless without connections. Stainless pipe fittings allow for changes in direction, branching, and diameter reduction. They must match the grade (304 vs 316) of the pipe.
Buttweld Fittings
Elbows, Tees, and Reducers welded directly to the pipe end. Best for high pressure.
Socket Weld / Threaded
3000# Forged Fittings. The pipe inserts into the fitting or screws in. Common under 2".
Stainless Flanges
Slip-On, Weld Neck, and Blind flanges. Used to bolt sections of pipe to valves or pumps.
Quick Navigation
Need Processing for this Pipe?
Stainless steel is difficult to cut and thread in the field. Most suppliers offer "Value Added Services" to prep the material before it ships.
Polishing
#4 Polish (180 Grit) for kitchen/sanitary use, or Mirror Finish for architectural work.
Saw Cutting
Band saw cutting to tight tolerances (+/- 1/16") so it is ready to weld on arrival.
Threading
NPT Threading on both ends (TBE) or One End (TOE) for standard screwed connections.