How to find the right Tube Fittings AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Tube Fittings
- Size by tube OD
- Tube fittings are sized to the tube's outside diameter, not its inside diameter or a nominal pipe size; measure OD with calipers. A 1/4 in tube fitting will not seal on 1/4 in nominal pipe or on hose with a 1/4 in inside diameter.
- Metric vs inch
- Metric and inch sizes are not interchangeable, even when they are close (6 mm vs 1/4 in, 12 mm vs 1/2 in). Near-miss sizes can seem to fit, then leak or blow off under pressure.
- Port thread standard
- Identify the port thread before buying: NPT (tapered), BSPP/BSPT, SAE O-ring boss or metric. Many threads look alike, and a mismatched thread will gall or leak no matter how tight it is.
- Material compatibility
- Match the fitting to the tube and the medium: brass for water, air and fuel gas; 316 stainless for corrosives and high pressure; plastic or PVDF for chemicals and lab use. Mixing dissimilar metals invites galvanic corrosion, and a soft fitting on hard tube will not seal.
- Pressure rating
- The working pressure of the system is the lower of the tube rating and the fitting rating; confirm both at your operating temperature. Fitting ratings fall at elevated temperature, and thin-wall tube can fail before the fitting does.
Brands that matter
- Swagelok: Benchmark for two-ferrule instrumentation compression fittings.
- Parker: Broad range covering CPI/A-LOK compression, 37° flare, EO bite-type and Legris push-to-connect.
- Hy-Lok: Two-ferrule instrumentation fittings in the Swagelok style.
- SMC: Large pneumatic push-to-connect range in metric and inch sizes.
- John Guest: Acetal push-fit fittings for water, beverage and RO systems.
- Anderson Metals: Common source for brass flare, compression and barb fittings in general plumbing.
What to avoid
- Buying by nominal pipe size when you have tube, or the reverse.
- Mixing ferrules, nuts and bodies from different manufacturers in compression fittings.
- Wrapping thread tape on flare or compression sealing surfaces, which do not seal on the threads.
Questions
What is the difference between tube and pipe fittings?
Tube is sized by actual outside diameter and seals with ferrules, flares or collets. Pipe is sized by a nominal size and seals on tapered threads or welds.