What is High Purity Welding?

By now you have heard us talk about our expertise in high purity welding. But, do most people really understand what High purity welding is? We will explain what high purity welding is, along with some of the acceptable standards for these high purity welds.

High purity welding is used in the semi-conductor and medical industries, to name a couple. High purity welding is done in a cleanroom setting where there is a controlled environment, preventing fewer contaminants from entering the weld area. This is important because the gases or fluids going through the tubing need to remain very clean. We have a great video that explains this as well below.

Weld quality and integrity is based mainly upon the penetration, oxidation, and bead of the weld. A weld is at its strongest when the bead fully penetrates the inner wall of the tubing. A partially penetrated weld is proven to be weaker.

In the industries that demand high purity welding, like semi and medical, the oxidation of the weld is another solid gage to the level of weld quality. Dirty welds, or welds with heavy oxidation, lead to contaminates getting into the contents of the system the tubing is servicing. To eliminate dirty welds, the welder purges them with an inert gas on the inside and outside, which helps reduce the oxidation levels to make a cleaner weld.

Understanding the Importance of High Purity Welding

It’s important to understand the many reasons why high purity welding is so important, and how you can ensure that your project is performed with the highest level of purity welds.

Why Is It So Important?

High purity welding is crucial to maintaining clean parts during the manufacturing process. Why? Because certain contaminants can be extremely damaging to metal tubing over time. When corrosive or oxidizing contaminants and other impurities get trapped inside the metal tubing, you risk the integrity of the entire system of which the tubing is a part. A dirty weld, or a weld with high oxidation can cause contaminants to spread throughout the entire system, and may cause a complete breakdown. The loss of time and money in such a case would be devastating.

Detailed Definitions and Standards for High-Purity and Ultra-High-Purity Welding

High-Purity Welding: Definition and Applications

High-purity welding involves the precise joining of metal components, such as tubing and fittings, in an environment that minimizes contamination. It is commonly used in industries like semiconductor manufacturing and medical device production, where the purity of gases or fluids within the system is critical. High-purity welding ensures contaminants are kept to a minimum, typically measured in parts per million (PPM).

Standards for High-Purity Welding

The standards for high-purity welding include:

• ASME BPE (Bioprocessing Equipment): Defines surface finish and cleanliness requirements, critical in biopharmaceutical applications.
• AWS D18.1/D18.2: Provides acceptance criteria for weld discoloration and smoothness, emphasizing sanitary standards.
• SEMI F81: Specifies materials and cleanliness for ultra-high-purity gas distribution systems in semiconductor manufacturing.

Elevating Precision with Ultra-High-Purity Welding

Ultra-high-purity welding takes the quality benchmarks of high-purity welding to an even higher level. It is used in microelectronics, pharmaceutical processing, and other industries requiring contamination control at the parts-per-billion (PPB) or parts-per-trillion (PPT) level.

Standards for Ultra-High-Purity Welding

• ASTM E595: Governs materials’ outgassing properties, essential in vacuum environments.
• ISO 14644: Defines cleanroom standards for environmental cleanliness during fabrication.
• Advanced Testing Methods: Includes helium leak detection and X-ray inspection to verify weld integrity.

Orbital vs. TIG Welding

Orbital welding is, by far, the cleanest and most efficient way to join tubes, flanges, elbows, joints and more, regardless of the application or industry. However, there are some applications where TIG welding is preferred, especially in cases where precise and/or extremely small welds are required, such as in welding projects for the aerospace industry, or when a weld joint is too tight and will not accommodate the orbital weld head.  

TIG welding is also often used for joining root passes, which are the most important part of a weld, and therefore the integrity and cleanliness of this type of is critical. When done properly, TIG welding is also a very clean process.

Detailed Explanation of Orbital GTAW and Its Advantages

Orbital Gas Tungsten Arc Welding (GTAW) is an automated welding process where the arc moves around a stationary workpiece, such as tubing or piping. This technique is highly favored in high-purity applications due to its precision and repeatability.

Advantages of Orbital GTAW

• Consistent Quality: Automated control ensures uniform welds across multiple joints, meeting stringent purity standards.
• Minimal Contamination: The sealed welding environment reduces exposure to external contaminants.
• Efficiency: Faster than manual TIG welding, orbital GTAW reduces production time without compromising quality.
• Precision: Achieves full penetration and smooth weld beads, essential for high-purity systems.

Challenges and Solutions of Orbital GTAW

Challenges

• Tight Spaces: Orbital weld heads may struggle to access confined joints.
• Skill Requirements: Setting up and operating orbital GTAW equipment requires specialized expertise.

Solutions

• Flexible Equipment Design: Modern orbital weld heads are designed to navigate tight spaces.
• Comprehensive Training: At Axenics, welders undergo extensive training to ensure proficiency with orbital GTAW.

Importance of Contaminant Control in Orbital GTAW

Contaminant Control Techniques

• Continuous Gas Flow: Inert gases shield the weld from atmospheric exposure throughout the process.
• Cleanroom Environments: Welding in Class 100 cleanrooms minimizes particulate intrusion.
• Separate Tools for Metals: Dedicated tools ensure no cross-contamination between materials.

Ensuring Weld Integrity

Every weld undergoes rigorous testing, including:

• Helium Leak Detection: Identifies micro-cracks that could compromise system purity.
• X-ray Inspection: Verifies weld penetration and bead quality.

Demand for High Purity Welding

Although high purity welding is ideal for any industry, there are certain industries which absolutely require high purity welding, due to the applications for which the metal tubing is being fabricated. The semiconductor, medical device and aerospace industries are the most notable industries requiring high purity welds.

For the semiconductor industry, where there is a high risk of micro contamination, and the medical and biotech industries, where bacteria can be a significant problem, orbital welding is typically used to provide the cleanest welds possible. In the aerospace industry, however, TIG welding is used more often, due to the small size of the majority of welds required.

High Purity Environment

To ensure that welds are of the highest purity, metal tubes and fittings should be welded in a high-purity, contaminant-free environment. Therefore, it’s important to work with a manufacturing partner that is dedicated to providing the cleanest possible environment for fabrication. High purity orbital welds should achieve no less than 100% penetration to meet industry standards and to create the cleanest possible welds.  

Axenics’ Class 100 Cleanrooms

At Axenics, we weld all tubing in a Class 100 cleanroom, using a proprietary cleaning process. We use 18 megaohms (MΩ) of deionized water to clean out each tube. Our certified welders also wear cleanroom suits to prevent any contamination from getting into the tubing and welds. We also flow argon through the inside of the tubing, and through the torch, in order to prevent oxidation from occurring.

By using this process, we are able to consistently produce high quality and high purity welds that meet or exceed our customer specifications.

Preparation Techniques for High-Purity Pipe Welding

Cleaning: The Foundation of High-Purity Welding

Thorough cleaning ensures no contaminants jeopardize weld quality. At Axenics, we use an 18 megaohm deionized water system to flush both the interior and exterior of pipes and fittings, removing dirt, grease, and particulates. This process ensures welds start from a clean slate, critical for maintaining integrity in high-purity systems.

Certified welders wear cleanroom suits to minimize human contamination. This practice is enhanced in Class 100 cleanrooms, which reduce particulate presence to near-zero levels.

Deburring and Surface Smoothing

Deburring removes sharp edges or imperfections at joints, ensuring a smooth, continuous weld bead. Surface smoothing, often achieved using specialized abrasives, further reduces the risk of contaminants clinging to material surfaces.

Purging with Inert Gases

Inert gas purging, commonly using high-purity argon, eliminates oxygen from the weld zone, minimizing oxidation. This step ensures cleaner welds and enhances bead penetration.

Inspection and Testing

Once materials are cleaned and deburred, they undergo visual inspections under magnification, testing for particulate levels, surface smoothness, and residual contamination. This ensures readiness for the welding process.

Minimizing Exposure to Contaminants During Welding

Short Arc Lengths and Controlled Weld Sizes

Maintaining a short arc length reduces heat exposure and prevents contaminants from entering the weld zone. Smaller weld sizes also limit surface area exposure to potential impurities.

Inert Gas Shielding

Shielding with inert gases, such as argon, protects the weld from atmospheric exposure, reducing oxidation and contamination risks. At Axenics, argon gas flows continuously around the tubing during welding to maintain a controlled environment.

Precision and Automation

Automated processes like orbital welding improve precision and consistency, minimizing human error. Orbital weld heads create a nearly sealed environment, ensuring contaminant-free welds.

Equipment Maintenance and Cleanroom Protocols

Properly maintained equipment prevents debris or residues from contaminating the weld. Dedicated tools and cleanroom practices further ensure contaminant control, such as separate workstations for different materials and strict cross-contamination protocols.

High-purity and ultra-high-purity welding are essential processes for industries demanding clean, contaminant-free systems. From preparation techniques to advanced orbital GTAW methods, maintaining stringent standards ensures the integrity and longevity of welded systems. By adhering to rigorous cleanliness protocols and leveraging cutting-edge technologies, Axenics delivers unmatched quality, reliability, and performance in high-purity welding applications.

If your industry or project calls for superior high purity welding, send it to a shop that has cleanroom capabilities. Saving time or cutting corners to reduce cost by going to just any weld shop will only come back to your desk in the end.

A trained eye can look at the beading of the welded joint and quickly tell the difference between a good weld and a bad weld. A good weld is very consistent in both spacing and width throughout the entire weld. If you inspect a bad weld, you will find a wide variation in the bead width and even the length.

*Comparison of weld beads:  picture from autospeed.com

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