Versatile electronic tools are employed by weld inspectors. The instruments emit sound or radio waves. As a reflected signals returns, the integrity of a weld area is confirmed or a concealed defect is exposed. Despite this service, visual testing strategies are held in high regard. Dependent on nothing more than a trained pair of eyes, why is this very human sense so important when there are machines to do the job?
Calling All Experienced Weld Auditors
An inspector’s visual acuity is worth a dozen testing instruments. That figure jumps higher if the testing authority is trained and experienced. First of all, those X-ray machines and radiographic testers are expensive. A visually conducted weld inspection doesn’t require monetary expenditure. In lieu of spending money, a seasoned technician unpacks his test kit. Handheld gauges and rulers come out of a zippered pouch. A flashlight flicks into life, then the visual inspection really commences. Next, a digital camera comes out so that the image can be recorded in living colour.
Determining the Benefits of Visual Testing
In the field of weld inspection, non-destructive tests are favoured whenever possible. A simple look at the fused join area comes first. After all, there’s no sense in calling in some expensive test rig until the weld fails its visual check. Does the weld satisfy all application criteria, as determined by the relevant engineering guidelines? That’s a requirement that can be satisfied via a pair of trained eyes. The size of the fused area is easy enough to read here, as is the surface conditions and coverage area of that weld. Electronic sensors are incredibly accurate, but a lonesome inspector, armed with a test kit, will easily discern this basic data.
Augmenting the Data Sets
Sure, the instruments mentioned earlier are built to elevate this action, but there are other tools, ones that don’t require a super-sensitive electronic eye. Still locked into a visual testing methodology, the tech pulls out his kit again. Mounted alongside the gauges and magnifying lenses, a small bottle of red dye aids the human eye. Used judicially, the possibly fluorescent liquid pools around a surface discontinuity so that a weld defect is clearly revealed. Equipped with flashlights, lenses, cameras, and gauges, welding inspection services progress far before ever calling upon a surface-penetrating gadget.
The human eye is a highly effective machine in its own right. Granted, an ultrasonic instrument can detect hidden flaws, but this human sense is also gifted with sensory prowess. While that electronically rendered image shows a thin weld defect, the eyes of the inspector are looking just as deep. They see colour irregularities around the fused area. They even see surface contrasts and textural flaws that a gifted electronic sensor misses entirely.
Accurate dimensions, delivered by the finest technical services, are critical to the functional life of any engineering project. But just what is a Dimensional Inspection service? Viewed from a fundamental aspect, the simplest dimensional measurements are carried out linearly. The distance from one supporting beam to its neighbour would fall under this spatial appraisal methodology. However, this is a science that quickly acquires a far more complex mode of execution.
What are Coordinate Based Measurements?
When an engineering structure requires an exactingly accurate dimensional measurement service, the call goes out for a coordinate-based measurement machine (CMM). Blessed with an ultra-high accuracy array of sensors, this special instrument spatially records the physical geometrical profiles of every feature within its range. That means the procedures carried out here are actualized in three-dimensional space. Imagine trying to match that all-seeing device with a tape measure and a notebook. It would take ages to match the dimensional gauging conducted by a CMM array.
Dimensional Inspection Services
The lay of a linearly arraigned bank of support stanchions is documented by employing a CMM solution. Traditional measurement techniques proceed while this digitally rendered service is conducted. The special tools exactly gauge the distance between nearby points. Meanwhile, curved surfaces are also viewed in three-dimensional space and measured. The angular differences are recorded and appraised, with the curvilinear data filling in any blanks during the survey. Exactingly recorded in this manner, the coordinates are fed into a CAD program and chewed until the whole structure can be rendered in real time as a visually accurate virtual construct.
CAD Rendered Evaluations
Structurally speaking, the advantages afforded by the system are many. The individual blades on a turbine can be rendered, then the structure becomes a dynamic model. Make changes to the turbine, test it to destruction, and know that the actual physical equipment lays untouched. Similarly, the CAD (Computer Aided Design) software is backed by engineering mathematics, so the stress factors experienced by a welded metal framework, perhaps a construct occupying space on an oil rig, become instantly accessible as a virtually controlled model. Used to simply measure every three-dimensional asset or to further analyze that data in a modelling program, dimensional inspection services are, indeed, invaluable.
Employed as a product conformity aid, a dimensional inspection service is a tool, one that operates as a geometrically accurate coordinate recording procedure. Electronic tools rule this spatial gauging domain, but the data can really be input from any source, be it an ultrasonic instrument or a simple hand-wielded measuring rule.
Multiple challenges greet a welding inspector when a project calls for his services. Have the right welding procedures been applied? Is the joint geometrically spot-on? These questions and more are checked off until the construct is certified as structurally rock-solid. Wait a minute, though, what about the mechanical and corrosion testing? It seems like the works not done just yet, not until we identify these twin threats.
Identifying and Addressing Corrosive Damage
Rust needs water and air to begin its spread. That’s a problem because these two corrosion enablers are literally everywhere. Worse yet, if this is an oil rig or some coastal framework, then there’s salt in the water. Salt accelerates material corrosion. So how do we inspect a weld area for this nasty oxide spread? First of all, iron corrosion appears as a highly visible stain. The orange oxide blooms and spreads. Left to eat into the weld faces, the rust will cause structural failure. Weld decay takes place, especially when the joint is pitted with tiny crevices. Stress fractures and ‘knifeline’ flaws also indicate a serious underlying condition. Address the issue by employing a corrosion inhibitor. Additionally, remove the corrosion source.
Mechanically Assured Weld Inspections
Mechanical integrity is a longstanding issue here, one that requires exhaustive attention. If the joint isn’t robust, as required by the engineering specs, then it becomes the weakest link in a critically important chain. Weak links crack, then they pull down the rest of that chain until it comes crashing down. In this case, a certified welding inspection visually evaluates the welding technique and the physical characteristics of the weld. Are there stress-induced micro-fractures on the surface of the joint? Is the solidified connection distorted due to torsional stress? Is it beginning to shear? The mechanical properties are further examined by calling in a subsurface testing rig, so all under-the-skin flaws are uncovered and recorded.
The act of applying a weld can actually amplify corrosion sensitivity on this occasion. The heat changes the metal surface ever so slightly, and the formerly heat treated alloy now becomes susceptible to rust. Then there are the environmental conditions, plus the installation circumstances to evaluate. If dissimilar metals are touching, galvanic corrosion occurs. Likewise, poor gas shielding practices can result in an oxidation gradient, so this flaw will exhibit a signature pitting pattern. Mechanically speaking, the corrosion weakens structural integrity. Eliminate the environmental factor, if possible. Otherwise, call in the welder, get him some extra training, and eliminate all poor jointing practices, including that poor gas shielding issue.
Certified weld inspectors have access to a wide range of non-destructive inspection services. Sure, a weld flaw can be visually detected, but even the keenest eye can’t see beyond a solid surface. NDT inspection services are designed to ‘see’ beyond the visible light spectrum. They use special sensors and scanning arrays to accomplish this impressive feat. Deemed a key inspection service, just what is this cutting-edge equipment all about?
Why is Non-Destructive Testing (NDT) Important?
If a pressure vessel or engineering asset is mechanically certified and commissioned, it’s classed as ready to install. How reckless would it now be to tear into a section of that metal frame? Even if the test involved nothing more than the removal of a maintenance hatch, the equipment could be compromised by this action. NDT procedures inspect weld seams and materials for flaws without altering the equipment configuration. Furthermore, these tests can be conducted while the equipment is on-site and locked into its processing framework, which represents a benefit that can’t always be offered by a more disruptive inspection routine.
Designing the Electronic Instrumentation
Imagine a range of non-destructive services that inspects welds for subsurface flaws. The equipment discovers microcrystalline defects in the sheet metal, locates imperfect welds, and seeks out hidden joint flaws. On the surface, that metal may look perfect, but below that surface, there could be a weak spot. NDT services use radiographic inspections and ultrasonic instruments to look through the solid material. They peer deep into the microscopic realm so that the contents of a metal component can be evaluated. Technologically speaking, the techniques employed here can detect any material imperfection, no matter how far below the surface that flaw is located.
Trained in All NDT Analysis Procedures
Entire chapters in engineering manuals are reserved for this critically important discipline. The science begins with liquid dye penetrants, then it takes flight with eddy current detection technology and radiographic scanning. Those latter sensory checks are commonly employed in hospitals as biological imaging procedures. Indeed, this field uses X-Ray science, radio waves, sound waves, and every other conceivable wave type on the electromagnetic spectrum. Equipped with a computer brain, the technically advanced tools can even create images of the subsurface scattering effect, just like an X-Ray.
If intelligently managed engineering resources have been exhausted while fabricating pressure-capable vessels and load-bearing structures, then those parts obviously are not meant to be compromised after they’ve been installed. Non-destructive inspection services allow engineers to conduct their weld and material analyzing routines without modifying those parts. Furthermore, the NDT routines look deeper than the human eye, so deep that they harmlessly peer past solid surfaces and into the potentially flawed internal geometry of a weld joint or a material form.
Like any other craft master, welding inspectors know everything there is to know about their chosen field. That metallurgical jointing expert probably started from the bottom as a welder. Working in the industry, certifications were gained, welding processes were mastered, and all applicable engineering codes were comprehensively assimilated. Today, that welding professional is backed by qualifications and certifications, the credentials that will open the door to new career opportunities.
Welding Inspection Jobs: What Does It Take?
Not surprisingly, this is a role that cannot be placed on the shoulders of an everyday welder. If a competent professional is getting the job done right, we still can’t simply pluck that skilled individual from the crew and assign him this position. As capable as that journeyman is, there’s no guarantee of technical proficiency. Similarly, we don’t pull a knowledgeable structural engineer from his office and say he’s the site welding inspector. This latter professional is academically capable, but where’s the practical experience? No, a welding inspection job needs a fully-rounded skillset, which is why the certification program exists as a merit-based career auditor, a qualification system that ensures the job claimant is both practically and academically accredited.
An Accredited CWI Professional
The CWI (Certified Weld Inspector) does visually inspect the metallurgical joints, but this fundamental inspection mode belies the true role of this exhaustively trained individual. If the training framework surrounding this professional could be made visible, we’d see an underlying platform built from years of practical welding experience. Alongside that block, there would be a second foundational support, one that illustrated process compliance and safety fidelity. Of course, these hypothetical musings are only that, a look at some possible capabilities. Certifications provide concrete proof of a wide range of competence-proven welding mastery. In short, this is a recognized accreditation program, one that requires investment, and that investment will take the form of money and time, but the resulting certification does place the successful candidate on one of the highest rungs of the welding career ladder.
There are no shortcuts here. Sure, a decade of welding experience smooths the career path somewhat, but that practically-minded worker now needs additional seasoning from the other side of the welding fence. Essentially, the candidate needs training in non-destructive testing technology, in structural engineering principles, and all other test methods. Armed with the practical and theoretical skills, paperwork and recorded documentation is the next order of business. It’s a diverse, multidisciplinary work position, the role of welding inspector, but the career path is also the ultimate culmination of years of hard work in the field of welding.