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Sanitary Welding Explained
While welding DIY and hobby projects at home may seem simple, the complexity escalates when the process specifications demand integrity, cleanliness, and safety of the finished product. This is where sanitary welding comes into play, a process that requires a higher level of precision and expertise.
Sanitary welding, a process that requires the highest level of cleanliness, hygiene, and weld aesthetics, is a crucial component in industries such as food and beverage, pharmaceuticals, biotechnology, and cosmetics. In this article, we'll delve into the practical applications and relevance of this branch of welding.
What Is Sanitary Welding?
Sanitary welding, also known as hygienic welding, is not just a welding process. It's a metal joining technique specifically designed to fuse sanitary metal pieces, typically in industries like food, pharmaceutical, medical, biotechnology, and more. The welders work with sanitary stainless steel, a material that's not only strong and corrosion-resistant but also lightweight, hygienic, and highly aesthetic, making it ideal for these industries.
The final goal of sanitary welding is to join stainless steel pipes or tubing with proper penetration and no defects or oxidation on top of the surface. Even the tiniest crevices, colors on the surface, voids, or lack of fusion open the door for contamination and can make the welded pieces unacceptable.
Sanitary Welding Standards And Codes
Since sanitary welding requires the highest levels of quality and cleanliness, organizations such as the American Welding Society have made a list of guidelines, standards, and codes. The primary role of welding standards is to ensure safety and uniformity in welding, and that also includes sanitary welding.
The first sanitary welding standards were based on The 3-A Sanitary Standards. The 3-A standards provide design criteria for equipment and processing systems based on ANSI requirements to promote acceptance by USDA, FDA, and state regulatory authorities. The 3-A committee worked with the American Welding Society (AWS) to provide the first sanitary welding standards, AWS D18.
The AWS D18.1 is titled "Specification for Welding Austenitic Stainless Steel Tube and Pipe Systems in Sanitary Applications." However, there are several variants based on multiple sanitary welding applications. As a result, we also have AWS D18.2 - Guide to Weld Discoloration Levels Snside Austenitic Stainless Steel Tube, or AWS D18.3 - Specification for Welding Vessels and Equipment in Sanitary Application. All these standards provide detailed instructions on weld properties required to produce sound and aesthetic welds required for sanitary applications.
In sanitary welding, welders can also consult the FDA FSMA (Food and Safety Modernization Act). FSMA rules are designed to make clear specific actions that must be taken to prevent food contamination. ASME Bioprocessing Equipment Standard standardizes specifications for the design and construction of new fluid processing equipment used in industries that require high sanitary standards.
Sanitary Welding Processes
According to the AWS D18 standards, sanitary welding is carried out by TIG or Gas Tungsten Arc Welding. If we take a closer look at the available arc processes, TIG welding is somewhat the most logical choice.
TIG welding uses a non-consumable tungsten electrode to form an arc, melt, and fuse the pieces. The entire operation is protected by a high-purity, non-reactive (inert) shielding gas such as argon. As a result, the weld pool and non-consumable tungsten are protected from atmospheric contamination. No cracks or porosity can endanger the integrity and quality of the weld.
The shielding gas protection provides a clean welding atmosphere, and with added weld preparation and cleaning, it is easy to reach the desirable level of cleanliness and aesthetics. Additionally, welders also employ back purging on stainless steel pipes. Shielding the back side of the pipe protects the inside part of the weld from contamination.
GTAW is also widely used due to its excellent heat control. A narrow heat-affected zone (HAZ) with limited amounts of heat means that the welds don't reach the critical temperatures at which they start oxidizing. Oxidation shows in the form of colors on top of the weld surface, and in sanitary welding situations, anything over chrome or, in specific cases, light gold color is unacceptable.
Source: https://wiki.dtonline.org/index.php/Heat_Treatment
Since TIG welding requires high skill levels, and there is little room for errors in sanitary welding, many turn to automated GTAW in the form of Orbital TIG Welding. Orbital GTAW welding is a semi-automated welding method for tubes or pipes that offers a high amount of precision. The specialized machine locks the tube or pipe to be welded while the welding arc rotates around the workpiece (ergo, the name orbital welding).
What makes orbital TIG welding a popular choice for sanitary welding is the ability to input the desired welding parameters. The machine is exact, and you can store and reuse the inputted parameters for the repetitive and highest-quality welds. Although much of the welding process can be automated, an operator's judgment is required to ensure weld quality and precision, so this is a semi-automated welding method for sanitary welding.
Laser Welding
Laser welding is one of the newer welding methods that uses the heat of the laser to melt and fuse pieces. Like TIG welding, the laser provides unmatched precision and limited heat input, which makes it a suitable choice for sanitary welding applications.
Similar to orbital TIG welding, the laser can be pre-programmed with desired welding parameters for repetitive welds. The entire process is clean, and the HAZ is highly concentrated and narrow, which produces barely visible welds. While this is practical on delicate, thin, and heat-sensitive alloys and metals, it can come short when welding thicker segments.
Electron beam Welding (EB Welding)
Electron beam (EB) welding is another advanced welding method that was found to be helpful in sanitary welding applications. This method involves using a high-speed stream of electrons that is tightly focused on the welding joint.
The advantages of EB welding in sanitary welding applications are that it is extraordinarily focused and narrow HAZ, it has excellent heat control, and it is maximally clean. The welding is highly automated and performed in a vacuum atmosphere, yielding unmatched and repetitive welds. However, it requires highly specialized equipment, which is profitable only in larger-scale applications.
Sanitary Welding Applications
The hygienic properties of sanitary welding make it a perfect choice for critical applications such as:
- Food and beverage,
- Pharmaceutical,
- Biotech
- Medical industries.
Sanitary welding has become increasingly important in maintaining high standards of hygiene and cleanliness in food processing plants and pharmaceutical and medical production. It is particularly crucial in handling and processing raw food materials, which can carry harmful bacteria that can cause foodborne illnesses if not properly contained.
Sanitary Welding In the Food And Beverage Industry
The growing global population has increased the demand for food. Expanding food production is essential to dealing with this issue, but a lot of attention has also been put to food safety.
Maintaining high standards of hygiene and cleanliness in food and beverage processing plants has become a paramount part of the food and beverage industry.
That's where sanitary welding plays a crucial role. The sanitary welds won't react and contaminate the food or beverage, which is essential in ensuring the safety of the final customers and consumers.
Some examples of sanitary welds in the food and beverage industry include vats, tanks, piping, and other food manufacturing or kitchen equipment. This equipment should not come in contact with porous surfaces, and it must be crevices, cracks, or corner-free to avoid retaining or collecting possible contamination or bacteria.
Sanitary Welding In Medical Industry
Sanitary welding is used in the medical industry to make medical instruments, surgical tools, lab equipment, and implantable devices. These devices and tools are typically made of exotic and delicate metals such as stainless steel or titanium. Since these can impact human life, there is absolutely no margin for error from quality.
Besides the highest quality, medical tools must be fit for function and aesthetics to promote ease of use. Low-profile welds with exceptional strength that are hardly visible are just the right choice for medical tools and equipment. After being used, the tools and equipment can easily be sanitized to ensure the health of future patients. That's why any welds and medical tools themselves must be resistant to corrosion, heat, and cracks.
Source: https://www.metrosteel.com.au/why-stainless-steel-is-so-important-in-the-health-industry/
Sanitary Welding In the Pharmaceutical Industry
Pharma welding, including sanitary welding, is much more different than ordinary welding procedures. This is highly specialized welding tailored to meet the rigorous standards of the pharmaceutical industry. It requires consistent, high-quality welds, and similar to the medical industry, the results are non-negotiable in pharmaceutical applications.
One of the types of sanitary welds in the pharmaceutical industry is the tubes and pipes used to transport chemicals. Like with the food industry, any cracks, voids, porosity, or corners can contaminate the transported chemicals. The drugs that are contaminated by the equipment pose a severe risk to the health of consumers.
Most sanitary welding for the pharmaceutical industry is carried out in a clean room to minimize the risk of contamination. The cleanroom provides a specialized welding atmosphere that adheres to rigorous cleanliness and contamination-free standards. The most used material is stainless steel due to its strength, corrosion resistance, and ability to withstand extreme temperatures and pressures.
Sanitary Welding In Biotechnology
Sanitary welding is also widely used in the biotech industry, and the goal is to provide clean production equipment and inhibit bacteria growth. Even a tiny amount of spatter can compromise product quality and lead to costly recalls, so bio-pharma vessels must be optimized for the highest standards.
Like pharma welding, biotechnology requires extreme cleanliness with zero defects. For the production of vaccines and biotherapeutics, maintaining a sterile environment is imperative.
Tips On How To Produce Sanitary Welds
While most of the sanitary welding we talked about requires specialized environments or equipment, you can produce the highest quality welds at your home. But, to do so, you will need the proper practices to keep the welds clean and safe. Here are some valuable tips.
1. Invest Time In Weld Preparation
To produce clean welds, you will need a clean welding environment. While it is hard to get the same results as welding in a vacuum or cleanroom at home, you can always thoroughly clean the surfaces and make sure there are no contaminants nearby.
So, before sanitary welding on stainless steel, make sure the surface, tools, and equipment are squeaky clean. You will need to remove all the dirt, dust, and oil to reduce the risk of contamination and spatter.
The more time you spend preparing the welds, the cleaner results you will get. This also means less time spent on rework and post-weld cleaning, and regarding the sanitary welds, that should be reduced to a minimum.
2. Use the Correct Metals And Alloys
Sanitary welds require sanitary metals and alloys, and as we noted, these are typically high-grade stainless steel. While stainless steel can be tricky to weld, its corrosion resistance, strength, and aesthetic make it a logical choice in many applications.
If you are using more than two materials, make sure they are compatible and easy to weld together. Welding dissimilar metals can be a nightmare, and sometimes, you will need to use advanced welding techniques such as EBW or Laser welding, which can be expensive for home applications.
3. Provide Good Shielding
A clean environment is nothing without clean and high-purity inert shielding. Inert shielding gases such as argon are non-reactive, which means they will protect the molten weld puddle and electrode from atmospheric gases and oxidation.
Since most sanitary welding applications include welding pipes and tubes, you will also need to employ a technique known as back purging. Back purging involves protecting the inside part of the pipe or tube with a shielding gas. Like the top of the weld, the inside part can also get contaminated by atmospheric gases, so you will need double shielding on the parts.
4. Use The Right Welding Technique
The appropriate welding technique for sanitary welding must provide cleanliness, precision, and reasonable heat control. TIG welding looks like a suitable solution, and the best part about it is that you can find inexpensive but competent machines for home use, so we certainly recommend YesWelder YWT-200DC Pro.
YWT-200DC DC Pulse High-frequency Lift TIG Capable TIG Welder
However, as you can see from the previous part of our text, sanitary welding can be performed using advanced welding techniques such as EWB, laser welding, and orbital TIG welding. These are typically reserved for high-end industries, delicate and extremely thin metals with a depth of penetration as small as 0.0001 inches.
Still, these advanced welding techniques require specialized machines and conditions to operate fully. Using this equipment for home applications is highly unprofitable, but for small businesses, it can be an ideal choice for sanitary welding.
5. Use Strict Inspection Methods
Sanitary welds must have proper penetration and tie-in and be critically defect-free. That means no cracks, voids, cavities, or spatter should appear on the surface or inside the welds. Each of these defects opens the door to contamination, bacteria, or corrosion, which can compromise the hygienic aspect of welded pieces.
While most defects can be noted by the visual inspection, nothing beats the proper inspection, such as radiographic or X-ray inspection, penetrants, or ultrasonic inspection. Besides the surface, these inspection methods can note internal defects such as inclusions, porosity, improper penetration, or lack of fusion.
Inspection is crucial in ensuring that sanitary welds are strong, durable, and resistant to any contamination. In the end, that's what distinguishes a sanitary from an ordinary weld.
Final Thoughts
Sanitary welding is not a separate welding process. It is a welding technique that is used to join sanitary pieces in critical industries such as medical, pharmaceutical, food & beverage, or biotechnical.
The sanitary welds must be uniform, strong, corrosion-resistant, and durable. The welds mustn't compromise or contaminate the chemicals or food that are contained in the vessels or pipes. To ensure that the welds are critically clean, they must be defect-free and follow rigorous standards.
That's why a lot of focus is on weld preparation, welding technique choice, and weld protection. Finally, the results are confirmed by various inspecting methods that can inspect both the surface and internal integrity of the welds.
🧐Sanitary Welding Explained FAQ
1. What is Sanitary Welding?
Sanitary welding, or hygienic welding, is a specialized technique for joining sanitary stainless steel, commonly used in industries like food, pharmaceuticals, and biotechnology. This process ensures proper penetration and defect-free welds, preventing contamination by eliminating surface imperfections such as crevices, discoloration, or voids. Sanitary stainless steel’s strength, corrosion resistance, and hygienic properties make it ideal for these applications.
2. What welding process is considered the most suitable for sanitary welding and why?
According to AWS D18 standards, TIG (Gas Tungsten Arc Welding) is the most suitable method for sanitary welding due to its precision and ability to maintain cleanliness. It uses a non-consumable tungsten electrode and high-purity inert gas, such as argon, to shield the weld pool from atmospheric contamination, ensuring welds are free from cracks and porosity.
Additionally, back purging is used to protect the inside of stainless steel welds from contamination. TIG welding also offers excellent heat control, minimizing oxidation and maintaining acceptable color standards for sanitary applications, ensuring both cleanliness and aesthetics.
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