Quality is one of Swagelok's six core values; here we offer up a checklist to make sure you get the best quality out of your tubing and what to look for
It's important to know what to look for in tubing quality and we have you covered with our checklist below. Still looking for more information on tubing, download our Tubing Data PDF.
There are 5 main parts to a tube fitting connection. Nut, back ferrule, front ferrule, and fitting body are all parts that are manufactured to exacting tolerances and standards at Swagelok. The fifth component, that Swagelok as a manufacturer has no control over, is the tubing.
Setting the tubing standards
There are a number of standards that apply to tubing depending on material, but we will focus on the stainless steel specs as this makes up the bulk of what we see being used in northern Alberta.
ASTM sets a number of standards for tubing, so when you get your tubing, it is always a good practice to check the lay line on the tubing for the ASTM standard to which it is manufactured. It should be printed on the tube, along with the heat number for the tubing.
For stainless steel tubing, ASTM A269 or A213 are common grades. A269 refers back to ASTM A1016 General Requirements, which gives us the following information:
- 13.1 – Finished tube shall be reasonably straight and have smooth ends free of burrs.
- ASTM A269 also gives guidelines for the tolerances of the tubing OD. It is +- 0.005in. Ovality is allowed to be two times the OD tolerance.
Even with the ASTM specs, there is a lack of standards and there can be variations in the quality of the tubing that you get. Tubing quality really does depend on the integrity and quality consciousness of the tubing supplier.
Tubing quality checklist
Before installing any piece of tubing into a Swagelok fitting, the installer should take a moment to take a look at the following items:
- Is the tubing seamless or welded? If it is welded are there any signs of corrosion or pitting along the weld bead? Can you see the weld bead on the OD? If there are, it may create issues.
- What is the hardness of the tubing? For best performance with a Swagelok fitting, it is recommended that the tubing not exceed a Rockwell hardness of 90 HRB.
- Make sure the surface finish is free of scratches. As the tube fitting seals on the OD of the tubing, scratches can result in potential leak paths.
- Check for ovality of the tubing. Oval tubing should not be forced into the tube fitting as it may damage some of the components.
- Check the OD and ID to make sure they are free of burrs. A burr on the OD can scratch and damage sealing components. A burr on the ID can get flushed downstream and damage O-rings or other seals in valves, regulators, or other components.
- Check the wall thickness to make sure it is sufficient for the pressures that the system will see.
- Check the tubing for concentricity, that is, check that the wall thickness is consistent all the way around the tubing. You don’t want a thick wall on the top of the tube and thinner wall on the bottom.
If you have any questions about the quality of the tubing you are using, please contact your local Swagelok supplier. Edmonton Valve has a number of tools that we can use to help improve the overall quality of your tube fitting connections.
For even more information, the Swagelok Tubing Data Sheet has lots of great information and pressure ratings for most common types of tubing.
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