3D Welding Requirements for Tubes & Fittings
November 7, 2025
3D Welding Requirements for Tubes & Fittings
"3D" in welding refers to the three key dimensional requirements for a weld joint before welding: Distance (Gap), Diameter (Misalignment), and Degrees (Angular Misalignment). Controlling these ensures a smooth, clean, and strong weld.
| Welding "D" | What It Means | Requirement / Why It's Important |
|---|---|---|
| Distance (Gap) | The space between the two tube ends inside the fitting. | • Must be very small (e.g., ≤ 1/16 inch or 1.5mm). • A large gap causes the weld to sag inside the pipe, creating a rough surface where bacteria can hide and grow. |
| Diameter (Alignment) | How perfectly round the two tubes line up with each other. | • Must be nearly perfect (e.g., ≤ 10% of wall thickness). • Misalignment creates a shadow or step inside the pipe. This creates turbulence, stops smooth drainage, and is a place for biofilm to start. |
| Degrees (Angle) | If the two tubes are perfectly straight and not bent at an angle to each other. | • Must be almost zero (e.g., ≤ 0.5 degrees). • An angular misalignment also creates an uneven internal surface and poor flow, leading to areas where water can stagnate. |
In short: The goal of 3D welding is to create a joint that is as smooth and continuous on the inside as the original pipe. This prevents bacterial growth, allows for complete drainage, and ensures the purity of the water for pharmaceuticals. This is achieved using precise cutting tools and skilled welders using a process called Orbital Welding (where a machine makes a perfect, repeatable weld).