The Importance of Materials Segregation

Process Industry Experts Share their Fabrication Pain Points

Materials segregation is a topic that is often overlooked in industry, discussions that get brushed under the rug in lieu of more important matters like the current price of nickel, product lead time, or what type of weld procedure will be used on a particular joint configuration.  Maybe it’s just assumed (and we all know what they say about ass-u-me) that your fabricator is doing a good-enough job of housekeeping. Why worry about it? Yet ensuring, not assuming, that the materials and tools used to build typical processing industry vessels and exchangers aren’t cross contaminating one another at any stage in the process is one of the most important things that your shop can do for you and your equipment.

We took the time to interview three reliability experts within the chemical process industry to better understand their true “pain points” on this topic.  As one chemical company engineer puts it, “In my experience, attention to materials segregation is one of a couple easy ways to differentiate between good fabricators and bad ones, especially as part of a shop audit and/or evaluating an unfamiliar fabricator.” Apparently, not all fabricators are created equally in this regard, “Many fabricators do not practice materials segregation and do not understand the need to do so,” says another producer company engineer, adding: “This may seem a little sarcastic, but it is true in my experience.”

His pain points include fabricators who do not understand cross contamination caused by improper practices in different fabrication operations. “For example, not coating or not cleaning the rollers between carbon steel and stainless steel or high alloy shell can forming,” he says, “or not segregating wire brushes, wheels, grinding disks, etc. used on carbon steel and excluding them from being used on stainless steel or high alloy materials.”

The last materials segregation pain point he shares, pointing out that there are plenty of others, is those who weld carbon steel temporary alignment attachments (“dogs” and “spiders”) directly to the ID surface of stainless steel or high alloy materials, without using a temporary stainless steel or alloy poison pad.

This engineer is not the only one who has felt the pain of cross contamination. A fixed equipment engineer with another site has a problem with fabricators who install hutches and tarps on the shop floor and advertise full segregation. “Typically, a carbon steel vessel is being fabricated next to these tarps and contaminating dust is airborne,” he explains. He adds that focusing on high level materials segregation on the shop floor during fabrication but slacking off on material storage and preparation is not acceptable. “It is not atypical to see alloy material stored on carbon steel racks or on water jet/plasma tables with steel jigs,” notes the engineer. Shops that move alloy materials with steel fork trucks and lifts is also something that he never wants to see.

Lastly, he warns about materials that fall through the cracks in the fabrication process: “For example, carbon steel plugs being installed in alloy vessels prior to a hydrostatic test,” “carbon steel tabs being welded or clamped to vessels for welding lead ground,” or “carbon steel tooling being used to assemble blinds prior to testing.” These and many other seemingly minor issues can cause major problems down the road.

In fact, for a topic that is often overlooked, there are numerous things to focus on when it comes to getting materials segregation right. One last engineer surveyed on the subject weighed in with his areas of concern. When asked about his top three pain points on materials segregation, he went the extra mile and provided the following five:

  1. Storing and working on high end alloys and reactive metals in the same spaces as carbon and stainless steels, introduces great potential for contamination of the exotic materials.
  2. Likewise, using the same tooling (clamps, brushes, burrs, etc.) indiscriminately from material to material. 
  3. Forming rolls, lifting clamps, storage dividers, should always be plastic covered to avoid contamination as well.
  4. The process of reducing the full-sized raw material into component pieces and finding that many shops are sluggish at transferring identification markings or do not have a regimented procedure or approach to maintaining semi-permanent markings on raw materials.
  5. Having a 5S approach to storage and marking is typically indicative of the top tier shops, whereby color-coding and placarding of the storage areas make it easy for the staff to follow the protocols.

Like these Chemical Processing Industry professionals, Ward Vessel & Exchanger takes materials segregation seriously and appreciates having a better understanding of the pain points our customers encounter here.  We strive to overcome these concerns and our employees are required to follow a detailed set of procedures that protect against any kind of contamination. These include inspection upon receipt of materials for proper packaging to prevent carbon contamination, proper storage and manufacturing practices (a full list is available for customers), as well as blasting to remove any contaminates from the exterior of completed equipment and/or exterior passivation.  In addition, all internal surfaces are inspected and cleaned.  Paying close attention to the details, right down to the chloride levels in NDE testing fluids and stencil markers, helps ensure that fabricated equipment remains contaminant-free.

When it’s time to load a vessel or exchanger for shipping, nylon straps are used for handling to prevent carbon steel contamination. Steel cables are to be used only when necessary and with an insulating material between the cable and the work piece. In addition, all truck drivers are also informed of the necessity for nylon straps in lieu of chains for securing their load. If chains are required, then we insist an insulating material be used between the chain and the work piece. It’s just one final but important detail we take into account in the materials segregation process, so that our customers aren’t the ones left feeling the pain.

For more information about Ward Vessel & Exchanger, contact us at 704.568.3001 or by email at