Calibrated Polyamide Tube Medifly PA668 Black (Ø 6×8 mm, PA6 MT, Black)

1. Purpose and Operating Principle

With an 8.0 mm outer diameter and a 6.0 mm inner bore, the PA668 model delivers optimal flow of compressed air and hydraulic fluids. Black PA6 MT nylon is less flexible than PA12 polyamide (minimum bend radius 100 mm vs. 50 mm for PA12) and has a narrower lower temperature threshold (−20°C), but outperforms it in rigidity and resistance to mechanical compression — making this tube preferable where the line is mounted stationary and not subject to frequent bending.

2. Technical Specifications

3. Design Features

Decoding the Medifly PA668 Black code:

Key design solutions:

• High rigidity and compression resistance — PA6 MT nylon outperforms PA12 in mechanical strength, important for rigid stationary lines.
• Resistance to oils and fuels — PA6 nylon has high resistance to mineral and motor oils, diesel fuel, and lubricants, extending its use to hydraulic circuits.
• High working pressure — 20 bar working pressure and 60 bar burst pressure with a margin over typical industrial pneumatic line parameters.
• Budget-friendly solution — at comparable strength characteristics, PA668 is cheaper than polyurethane equivalents.

4. Installation Recommendations

1. End preparation. Use a dedicated guillotine-style tube cutter for a clean 90° cut — an uneven end on rigid nylon noticeably compromises the fitting’s seal.
2. Fitting types. The calibrated 8.0 mm outer diameter ensures full compatibility with all standard push-in fittings from European and Asian brands.
3. Bend radius. Minimum bend radius is 100 mm; because PA6 is less flexible than PA12, do not allow sharper bends during installation.
4. Account for the lower temperature threshold. The working range starts at −20°C — at lower temperatures the material becomes more brittle, unlike PA12 (down to −40…−60°C).

5. Comparison with PA12

• PA6 MT (this tube) — higher rigidity and compression resistance, but lower flexibility (100 mm bend radius) and a narrower temperature range (from −20°C).
• PA12 — higher flexibility (bend radius from 40–50 mm), wider temperature range (down to −60°C), but usually more expensive at comparable pressure ratings.

6. Common Mistakes

• Installing in conditions of frequent bending and vibration — rigid PA6 is designed for stationary lines; polyurethane or PA12 is better suited to moving modules.
• Operating below −20°C — increases the risk of nylon cracking.
• Cutting with a substandard tool — an uneven end causes a leak at the fitting under 20 bar working pressure.

7. Applications

• Rigid stationary pneumatic lines — industrial and workshop compressed air networks.
• Hydraulic circuits with oils — thanks to PA6’s resistance to mineral and motor oils, diesel fuel, and lubricants.
• Industrial equipment — anywhere a strong but budget-friendly calibrated tube is needed.

8. Expert Opinion

Vitalii Boluchevski, lead engineer at Acvatron SRL (18 years of experience): “The Medifly PA668 Black polyamide tube at 8×6 mm caliber, made of PA6 nylon, is an excellent budget-friendly and reliable solution for rigid stationary pneumatic lines.”

9. FAQ

1. What’s the main difference between PA6 and PA12? PA6 polyamide has high rigidity and resistance to mechanical compression, but is less flexible (100 mm bend radius vs. 50 mm for PA12) and has a higher lower temperature threshold (−20°C).

2. Is the PA668 tube compatible with 8 mm quick-disconnect fittings? Yes, the calibrated 8.0 mm outer diameter ensures full compatibility with all standard push-in fittings from European and Asian brands.

3. Can this tube be used for hydraulic oils? Yes, PA6 nylon has high resistance to mineral and motor oils, diesel fuel, and lubricants.

4. What’s the maximum pressure the PA668 can withstand? In the dry state, at room temperature (+23°C), the working pressure is 20 bar, and the burst pressure is 60 bar.