2.1. Material Identification and Traceability
Identification means the ability to determine that the specified material grade and size are being used. Section 6.1 of the Code of Standard Practice states: "The fabricator shall be able to demonstrate by written procedure and actual practice a method of material identification, visible up to the point of assembling members." The Code goes on to describe in further detail the requirements.
Traceability means the ability to identify a specific piece of steel in a structure, throughout the life of the structure, and its specific mill test report (MTR). As such, traceability requirements are significantly more expensive than the identification requirements discussed in 2.1.1. The owner should clearly understand the differences, limitations and relative costs involved.
Traceability is not a requirement in the AISC Specification but, when required, must be clearly specified in the contract documents prior to the ordering of material. The following elements of traceability should be selected only as needed:
1. Lot traceability vs. piece-mark traceability vs. piece traceability: Lot traceability means that the materials used in a given project can be traced to the set of MTRs for that project. Piece-mark traceability means that the heat number can be correlated for each piece mark, of which there can be many individual pieces. Piece traceability means that the heat number can be correlated for each piece, which effectively demands separate piece marks for each piece. Each of these three successive levels of traceability adds significant costs. Piece traceability, the most expensive option, is necessary only in critical applications, such as the construction of a nuclear power facility. Piece-mark traceability is often specified for main members in bridges. Lot identification is most common in other applications where traceability is required.
2. Main-material traceability vs. all-material traceability: Main-material traceability means that beams, columns, braces and other main structural members are traced as specified above. All-material traceability means that connection and detail materials are also traced as specified above. All-material traceability, the more expensive option, is necessary only in critical applications, such as the construction of a nuclear power facility. In other cases, main-material traceability is sufficient when traceability is a requirement.
3. Consumables traceability means that lot numbers for consumables such as bolts, welding electrodes and paint can be traced. This is necessary only in critical applications, such as the construction of a nuclear power facility.
4. Required record retention defines the level of detail required in documenting traceability (who, what, when, where, how, etc.).
5. Fool-proof record retention vs. fraud-proof record retention: Fool-proof record retention means internal verification of records. Fraud-proof record retention means external certification of records. Fraud-proof record retention is necessary only in critical applications, such as the construction of a nuclear power facility. In other cases, fool-proof record retention is sufficient when traceability is a requirement.
Each heat of steel produced by the mill is tested for chemical content and mechanical properties, and the results are recorded on a MTR, which is provided to and maintained in the records of the fabricator. Each piece that is rolled from this heat is then labeled with an identification mark that relates to the corresponding MTR. The fabricator applies an identification mark to each piece. Because this piece mark remains with the piece throughout the fabrication and erection process, the material is traceable back to the MTR for that individual piece.
Many connecting elements and similar fittings are too small to accommodate the marks to identify the piece from which they were cut. Additionally, such items are commonly made from stock materials with marks that may have inadvertently been abraded or lost during years of storage. In such cases, the fabricator provides written certification that the stock material meets the contract requirements.
Manufacturers of consumables such as bolts, welding electrodes and paint provide documentation as to the content and specification compliance of their products. This documentation is provided to and maintained in the records of the fabricator.
The packaging in which the products are shipped is referenced to this documentation. In some cases, the fabricator may purchase materials through a steel service center. When this is the case, the steel service center must transmit the necessary documentation from the manufacturer to the fabricator.