Welding Techniques

Avoiding the Unseen Dangers Of Contamination

After spending time, effort, and resources to bring an idea to life, the last thing you want is to have your project stalled because of contaminated materials. Manufacturers must develop strict protocols to prevent contamination of any manufacturing process, welds, or finished surface. Failure to plan can have catastrophic effects on the functionality of the finished product.

Contamination vs. Cross Contamination

Contamination occurs when a foreign substance, such as oil or rubber, is inadvertently introduced into the manufacturing process. Cross contamination, on the other hand, occurs when metal from one application — carbon steel, for example — is accidentally transferred onto a non-compatible metal, such as stainless steel.

Both contamination and cross contamination can negatively impact the finished part's performance, durability and lifespan. Among the possible consequences of contamination and cross contamination are:

  • Unexpected corrosion.
  • Weld failure or cracking.
  • Liquid metal embrittlement in elevated temperature services.
  • Contamination of sensitive final-use products in industries where cleanliness and purity are critical. If oil or rust contaminates a part made for a pharmaceutical freeze dryer, for example, then the drugs produced on that equipment are contaminated.
  • Spread of detrimental materials throughout a larger system of equipment. If a contaminated part were to enter a nuclear reactor, for example, that contaminant could quickly spread throughout the entire reactor.

Best Practices for Preventing Cross Contamination

There are six different approaches to keeping the wrong materials from being introduced into manufacturing processes:

  1. Conduct high-risk activities away from sensitive parts: Operations like grinding are especially prone to generating airborne particles, which can settle on sensitive materials. Grinding equipment should be used and housed away from vulnerable materials.

  2. Use color-coding to classify tools: A well-accepted industry practice is to assign colors to tools based on their purpose or previous contacts. Abrasives are painted with one color so employees are alerted not to move them from carbon steel to stainless steel. Another color distinguishes tools for grinding that haven't been (and cannot be) used on a different type of material.

  3. Develop strict handling practices: Employees should refrain from sliding parts along surfaces or other parts made of incompatible materials. A stainless steel part should never be dragged across a carbon steel table, for example. Installing shims between clamps and parts can prevent unwanted contact.

  4. Segregate sensitive materials: Materials like titanium are especially vulnerable to cross contamination and must be totally pure. Some applications require these hyper-sensitive materials to be completely segregated in storage.

  5. Purify the machines themselves: Manufacturers who know their machines inside and out can go even further in preventing unwanted exposure. For example, coolant is used to prevent tools from wearing out, and that coolant can collect contaminants. When working with sensitive materials like titanium, it may be necessary to flush out and replace the coolant to avoid any particulate matter from metal that was machined earlier that day.

  6. Cover materials with plastic: Simple plastic wrapping can go a long way in preventing airborne grit and dust from settling onto components tools or materials.

Contaminants can devastate an otherwise perfect manufacturing process. In order to avoid contamination and cross contamination, manufacturers must be strict and methodical in developing and following a non-negotiable series of preventative measures to maintain absolute control over what goes into — and doesn't go into — each and every step of manufacturing.

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