This page covers one tube: unfilled PA12 (nylon 12) semi-rigid tubing, 6 mm OD x 1.25 mm wall, rated 70 bar working pressure at 23°C to DIN 73378 dimensions. It serves compressed air, fuel and oil transfer, central lubrication feed lines, and low-pressure hydraulic circuits. For grease-filled branch lines, see the heavy-wall 6×1.5 mm PA tube page. For light-duty 6×4 mm nylon tube, a different size reading, see the 6 mm nylon pipe page. For coil form, see the helical coil nylon pipe page.
DIN 73378 is the dimensional standard this PA12 lubrication tubing is made to — when a parts list calls for DIN 73378 tubing, a 6×1.25 mm semi-rigid PA12 tube is the match.
Size: Reading the 6×1.25 Code
The code 6×1.25 reads as OD x wall thickness: 6.0 mm outside diameter, 1.25 mm wall, 3.5 mm inside diameter. OD tolerance is +/- 0.2 mm. The 6 mm nylon pipe page uses a different code: 6×4 reads as OD x ID. Confirm which convention your drawing follows when ordering.
Pressure and Temperature Ratings
The 70 bar working pressure applies at 23°C (1,015 PSI). Minimum burst pressure is 210 bar. These are different statements, and we quote no ratio between them. As temperature rises, working pressure comes down per the DIN 73378 correction factors:
| Continuous Temperature | Correction Factor | Working Pressure |
|---|---|---|
| -40 to +20°C | 1.00 | 70 bar |
| +30°C | 0.80 | 56 bar |
| +40°C | 0.60 | 42 bar |
| +50°C | 0.50 | 35 bar |
| +60°C | 0.45 | 31.5 bar |
| +70°C | 0.40 | 28 bar |
| +80°C | 0.33 | 23 bar |
| +100°C | 0.25 | 17.5 bar |
Two rows matter: +70°C is the ceiling for water-based media; +100°C at 17.5 bar is a short-term peak only. The material itself peaks at +110°C short-term.
Unfilled PA12 Material
The tube is extruded from virgin unfilled PA12, no glass fiber or mineral filler. It is semi-rigid, Shore D 63 – 74, density about 1.01 – 1.03 g/cm3. Saturation water absorption is under 0.3% against roughly 3 – 4% for PA6, so PA12 holds its dimensions and fit in humid service.
Media Compatibility
Suitable media include compressed air, vacuum, fuel transfer, central lubrication lines, and low-pressure hydraulic circuits, plus mineral and synthetic oils, fuels, and synthetic lubricants. PU tube degrades where petroleum products touch it; PA12 does not. PA6 takes on far more moisture and swells.
When PTFE Makes More Sense
PTFE tube resists nearly all chemicals and up to +260°C, but it is more expensive, holds little pressure in thin walls, and passes gas. Choose PTFE only for strong acids below pH 2, strong alkalis above pH 12, or service above +120°C. Within these ratings, PA12 is the practical option.
Honest Limitations
Four boundaries before ordering:
- Continuous service above +60°C belongs on the heavier-wall 6×1.5 mm tube, not this one.
- Water-based media stop at +70°C and 28 bar working pressure.
- This is an oil and air line. Grease-filled branch lines use the pre-filled heavy-wall version.
- Strong acids, strong alkalis, or service above +120°C call for PTFE.
If your application sits near these edges, send us your media, temperature, and pressure details to confirm suitability.
What Is Supplied
Standard colors are black, natural, blue, red, yellow, green, and orange. Black is the recommended choice for outdoor UV exposure. Standard coil lengths are 10 m, 25 m, 50 m, and 100 m, and custom cut lengths are available on request.
Frequently Asked Questions
What does 6×1.25 mean?
It reads as OD x wall: 6.0 mm outside diameter, 1.25 mm wall, 3.5 mm inside. The 6 mm nylon pipe page instead codes 6×4 as OD x ID. Confirm the convention when ordering.
Is 70 bar the rating at any temperature?
No. 70 bar applies at 23°C only. Use the DIN 73378 factors above as temperature rises: 35 bar at +50°C, 23 bar at +80°C, 17.5 bar at +100°C for short peaks.
How does 210 bar burst relate to 70 bar working?
Two separate statements: 70 bar is the continuous working rating at 23°C, 210 bar minimum is the burst pressure. We state them side by side, not as a ratio.
Should I pick PA12, PU, or PA6 tube?
For fuel, oil, and lubrication lines, PA12. It resists petroleum products, while PU degrades on contact with them. PA6 absorbs much more moisture.
When should I switch to PTFE tube?
Only for aggressive chemistry or heat: strong acids below pH 2, strong alkalis above pH 12, or service above +120°C. PTFE covers those but is more expensive, thin-wall, and gas-permeable.
Does outdoor installation need anything special?
Pick the black color. All standard colors work indoors, but black is the recommended option where the line sees outdoor UV exposure.
Can this tube carry grease?
It carries the oil and air side of central lubrication systems. For grease-filled branch lines, order the pre-filled heavy-wall 6×1.5 mm tube instead.
How much pressure is left above +80°C?
At +80°C the corrected rating is 23 bar. At +100°C it falls to 17.5 bar for short-term peaks only.
How do I select fittings?
Choose push-in or compression fittings by the 6 mm outside diameter. Our grease line tubing and fittings selection guide walks through matching tube and fitting combinations.
Who is IsoHiTech and how do I order?
IsoHiTech Lubrication Systems is a lubrication equipment supplier founded in 2023, engineering since 2006. Request a quote through our quote request page or send drawings to inquiry@isohitech.com.
