What is a flawed specimen?
Today I would like to address the concept of making intentionally flawed NDT flawed specimens. Anyone can make a bad weld or product. This is true in concept but making a flawed specimen with accurate dimensions with no distractors other than the intended flaws to gauge an NDT Technician’s performance or ability to properly locate, size and dispatch said specimen to a specific code, procedure or industry standard is another thing all together.
We commonly use blocks or product segments with notches, side drilled holes (SDH), flat bottom holes (FBH) and other discontinuity simulations for calibration to establish a standard response or detectability size. Setting an accurate reference is paramount to feting quality accurate inspection regardless of method.
How are flawed specimens used in your industry?
So, in comes the Intentionally Flawed Specimen, why do we need accurate realistic flawed specimens. No matter what industry you are in you need to train our technicians on material and flaws found in the particular. Field removed real flaws are great when you can get them. But far too few of these can be harvested to train all the technicians across the country and around the world. Sports analogies always work for me but to be the best you have to train with the best. Practice like its game day. That is why we provide NDT Flawed specimens in kits, individual pieces and custom flawed specimens to meet specific projects with specific needs for performance demonstration, Probability of Detection or training for a particular qualification.
So, how do we make our flaws?
Well, to be totally honest, many of those techniques are proprietary and have been developed over our 36+ years history. Many of the welding flaws like porosity, slag, lack of fusion, incomplete penetration, undercut and tungsten inclusions are made just like they are in normal production. Nothing really too fancy except we place them incredibly accurate for both location and size. Cracks are little different and we have developed several different techniques and types to simulate specific types of cracks. We produce most of our cracking using mechanical fatigue, thermal fatigue or hybrid type method. For some of the industry driven crack specimens like HIC (Hydrogen Induced Cracking or SCC (Stress Corrosion Cracking – Intergranular or Trans-granular) we use techniques we call “CRAZE Cracking” since we can’t exactly model the environment in an effective timely manner that is required to develop the two previously mentioned cracking modes. We are very successful in developing flaws that model the NDT responses for different NDT Methods used to evaluate assets for these flaws though. We have also developed what we call “Accelerated Corrosion” which produces more realistic pitting, corrosion and erosion. We can even age the exterior or interior of a tube or pipe to simulate it having been in service. What is most extraordinary is the accuracy we can replicate these flaws. Virtually all flaws are mechanically measured and verified so regardless of what NDT Method being used we know the actual size of the flaw manufactured. We call this the “Flaw Truth”. Manufactured flaws over the years have been sliced and diced confirming the manufacturing tolerances are highly accurate.
Manufacturing our NDT Flawed Specimen to meet our customers intended purpose is paramount to our core values here at FlawTech America. We constantly work on developing new techniques and type of flaws to meet industry needs.
Fabricated or manufactured flaw specimens are an effective, reasonable cost alternative to real world flaw specimens which can be very expensive, limited in numbers and difficult to ascertain the true size of the flaws without destroying the sample. Waiting for demolition or deactivation of assets is not a timely option in order to train, qualify and validate qualification of NDT practitioners required to service our industry.