September 9, 2011
Weld inspectors, especially those who are new to the trade, put a lot of emphasis on the equipment needed to do the job: flashlight, mirror, high-low gauge, pit gauge, bridge camera, and a borescope. However, this isn’t the entire toolkit. A weld inspector also must be cognizant of the applicable codes, knowledgeable about the project owners’ specifications, and should carry a personal log book for making notes about conversations and inspections.
The quality control profession is far from static. The need for quality control inspectors is increasing and the field is growing. As rising numbers of owner-users, manufacturers, and contractors learn that well-trained and knowledgeable quality control inspectors have an impact on the quality of a facility or project, new job opportunities are created.
Anyone interested in becoming an inspector should familiarize himself with the necessary tools. Merriam-Webster’s definition of a tool is; “Something (as an instrument or apparatus) used in performing an operation or necessary in the practice of a vocation or profession.”
When you ask people in the construction industry about inspection tools, common answers are a flashlight, mirror, high-low gauge, pit gauge, bridge cam, and borescope. Often they leave out the most important and critical tools: codes, owner specifications, drawings, bills of material, and a personal log book.
As any welding inspector knows, having a good flashlight is important when looking through a window left in an open butt joint to examine the internal of a root bead. Also, when used properly, a flashlight can help to spot undercut at the toe of a weld. Likewise, a mirror is handy for a visual inspection of the internal bead of a pipe weld, test coupon, and any weld near an obstruction that prevents a direct view.
A pit gauge or a bridge cam is handy for measuring pits in the wall of base material, undercut, or the amount of reinforcement of a weld, whether it’s convex or concave. As borescopes become more affordable and smaller in size, they are being used more frequently to do visual inspections where it is impractical or impossible to see with a mirror and a light.
All of these tools are useful, but their usefulness is limited if the inspector isn’t familiar with the codes, specifications, and bill of materials.
The most important tools are not physical tools, but documentation and knowledge. The relevant documents provide recommended and required construction practices; describe the correct use of inspection instruments; and provide acceptance criteria for an inspector. Others are the construction codes and the owner’s specifications.
Codes. Welds are engineered to meet various criteria depending on considerations such as expected service life, environment, temperature, strength, and system cleanability. These are determined through codes written by entities such as the American Society of Mechanical Engineers (ASME), American Welding Society (AWS), and the American Petroleum Institute (API). A good understanding and working knowledge of these codes is a necessity for a weld inspector.
Most projects have to meet several codes and national standards. For example, a pharmaceutical plant may use ASME Biopharmaceutical Equipment Standard ASME B31.1, ASME B31.3, ASME Sec. I, Sec. V, Sec. VIII, and Sec, IX; and AWS D1.1.
The inspector does not need to have all of these codes memorized, but must have a working knowledge of each of them, with a special focus on details about acceptable procedures for preparation, welding conditions, and acceptance criteria.
Owner’s Specifications. An owner-user often has specifications that are more stringent than, or supplementary to, commonly accepted construction codes. Inspectors must read the owner’s specifications, including engineering drawings and bills of material. This is critical to ensure all job-, company-, and site-specific needs are met. A copy of all specifications must be readily available to the inspector. It is a good practice for the inspector to make notes about the owner’s specifications.
Personal Log. An inspector’s typical day is busy and involves examining many types of weld parameters—weld joint fit-up, internal root beads, final welds, and hydrostatic test results, to name a few—and having many conversations. To keep the details straight for future reference, the inspector should make comprehensive notes in a personal log. Such a log can be invaluable for future reference, especially if a dispute arises.
Inspectors aren’t the only ones who need to be familiar with codes, specifications, and standards. Everyone involved in the project should be familiar with the codes that apply to the job, which ultimately prevents rejects and therefore rework.
The cost of rework is summarized in this equation:
(Hc ¥ 3) + (Co ¥ 2) + (Mo ¥ 3) + (T ¥ 2) + (Ma ¥ 2) + (Lt ¥ 1) = C
Hc = Labor-hours of original work converted to cost
Co = Consumables for original work (e.g., electrodes and shielding gas)
Mo = Mobilization from ongoing work to rework
T = Required nondestructive examination of repair, including visualinspection
Ma = Material for original work and new material for rework
Lt = Lost schedule time in labor-hours, converted to cost
C = Total cost of repair or rework
Preventing rework is critical to keeping projects on budget and on schedule.
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