Capillary Tube — ASTM A269 / A632
Capillary tube — small-bore tube for instruments and medical use. Capillary tubes have very small diameters and walls for instrumentation, thermometry and medical devices.
- ASTM A269 / A632
- 7 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is a capillary tube?
A capillary tube is small-bore tube for instruments and medical use. Capillary tubes have very small diameters and walls for instrumentation, thermometry and medical devices.
Standards for capillary tubes
| Dimensions | ASTM A269 / A632 |
|---|---|
| Material — stainless | ASTM A312 · tube ASTM A269 / ASTM A213 |
| Material — duplex | ASTM A790 · tube ASTM A789 |
| Material — nickel alloys | ASTM B423 (825) · ASTM B444 (625) · ASTM B622 (C276) |
| Material — carbon & Cr-Mo | ASTM A106 · ASTM A333 · ASTM A335 |
| Certificate | EN 10204 3.1, or 3.2 with third-party inspection |
Capillary Tube: What to Know Before Ordering
- Very small OD
- Bright annealed
- Coils or cut lengths
Capillary Tube Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| SS 904L capillary tube | ASTM A269 · A213 where supported (N08904) | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 capillary tube | ASTM A213 · A269 · A249 | General corrosion resistance, food, water and architectural work |
| SS 304L capillary tube | ASTM A213 · A269 · A249 | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S capillary tube | ASTM A213 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L capillary tube | ASTM A213 · A269 · A249 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 capillary tube | ASTM A213 | High-temperature service between 425 and 815 °C |
| SS 347 capillary tube | ASTM A213 | Welded high-temperature piping in refineries and power plants |
Capillary tube — questions buyers ask
What is a capillary tube?
A capillary tube is small-bore tube for instruments and medical use. Capillary tubes have very small diameters and walls for instrumentation, thermometry and medical devices.
What sizes are capillary tubes?
Commonly 0.3 – 6 mm OD with thin walls, supplied in coils or cut lengths.
Which grades are capillary tubes available in?
SS 904L, SS 304, SS 304L, SS 310 / 310S, SS 316 / 316L, SS 321, SS 347.
Which standard covers capillary tube dimensions?
ASTM A269 / A632. The material standard depends on the grade.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026