Visual Testing (VT) technicians often need to inspect internal welds, welds that are often deep inside a part or assembly, or are in some way not easily accessible. In these situations, borescopes are invaluable remote visual inspection tools, allowing you to get “your eye inside” the part.

Borescopes are essentially the same as medical endoscopes but are intended for industrial use to inspect any type of bore. They allow production or quality control personnel to look inside small and complex parts and to visually inspect with great detail. Borescope diameters range from about 0.5 up to 10 mm, and lengths range from about 2 in. to more than 50 ft. There are three basic types: rigid borescopes, flexible fiberoptic borescopes, and flexible and rigid video borescopes.

Rigid borescopes use a series of relay lenses to relay the image down a long, narrow tube. They are always the best option if you have a straight path to inspect. Rigid borescopes have the highest image quality, lowest price, and are more durable. Some can be used both for straight ahead (0 deg) and 90- deg viewing of the welds. These scopes can be used either by eye or they can be attached to a video camera. In a factory type setting, a video camera is the way to go.

Flexible fiberoptic borescopes use a bundle of optical fibers to relay the image down a long, flexible tube. They are necessary when the tubes are bent, or you just have to get around some type of a bend or obstruction. They have lower resolution due to the use of fiber optics rather than conventional lenses. Fiberoptic scopes are higher priced and are typically more fragile, but they will get you around the bend if that is what you need to do. Many hydraulic, fuel, and pharmaceutical applications utilize bent tubes with welded fittings. These flexible scopes are just the ticket for that type of inspection.

Video borescopes incorporate the latest technology. Rather than using the relay lens systems used in rigid borescopes, or a fiber-optic image guide as in fiber scopes, video borescopes have a micro video camera at the tip of the scope. This gives the user a flexible scope with much better resolution, displayed directly onto a video monitor, handheld or desktop device, or laptop or desktop computer. Video borescopes deliver the quality of a rigid scope, but with a flexible shaft. They often have two- or four-way articulation allowing the user to literally steer the scope around bends. These systems offer convenience and portability. They feature everything you need to conduct a remote visual inspection, and the ability to capture still images or video, all in one small, lightweight, handheld package.

One of the most common applications of borescopes is the inspection of orbital welds inside stainless steel tubes and fittings. These tubes are used in a variety of fields, including aircraft fuel systems, power generation, hydraulic systems for aviation, heavy equipment, pharmaceutical manufacturing, food processing, chemical processing, and oil and gas equipment. Indirect visual testing with a borescope is often the only way to look inside these difficult-to-reach parts and systems.

In most cases, operators employ orbital welding with an integral filler metal, machined directly into a fitting. VT technicians examine each weld to ensure there’s no lack of penetration of the weld bead through the base metal, which typically is titanium, nickel, or stainless steel. For instance, the key factor in making high-quality welds in titanium is cleanliness. Thus, VT technicians look for weld porosity or contamination.

Performing an indirect visual inspection on the first workpiece gives the welder or welding operator immediate feedback on whether the penetration is acceptable without waiting for radiography results. Doing so provides immediate feedback, reduces the cost of rework, and decreases the likelihood of a nonconforming part ever reaching the customer. This allows the operator to change welding parameters as necessary to ensure a conforming part.

There is also a big benefit to adding video capability to the indirect visual inspection process with the addition of a video system attached to the borescope. Video systems provide blown-up views, so they give inspectors an enhanced picture of welded joints. Welders can just lay down a tube and twirl the scope around to inspect their work easily and quickly. The video system is also a great tool for welder training on visual requirements.

By using a borescope, the VT technician can get a great view of the heat-affected zone (HAZ), and can clearly see slag and voids in an imperfect weld.

Another application for indirect visual inspection is the manufacture of the tubing itself. The majority of stainless-steel tubing is manufactured using the “welded and drawn” method. Borescopes can be used to inspect the longitudinal weld joint inside these tubes as part of the quality control process. This is particularly important in medical tubing.

Borescopes are used to inspect internal welds and braze joints in all kinds of assemblies in automotive, aviation, and heavy equipment. Typical examples include inspecting welds inside large aircraft oil coolers, radiators, and other heat exchangers. Structural welds that are difficult to access can be inspected as well.

A wide variety of miniature medical products are manufactured using microwelds. Medical products such as endoscopes and endoscope accessories, microvalves, and arterial stents are a few examples. Very small-diameter borescopes allow visual inspection of these critical components.

Video borescopes are also very useful for indirect visual inspection of welds in structural steel in buildings, bridges, etc., in situations where you simply are not able to get a good look with the naked eye. The videoscope allows you to see the problem, capture the image, or video the entire inspection. The key to proper indirect visual inspection is choosing the right scope for your particular application. VT technicians sometimes want one tool to do it all. That’s a nice concept, but it doesn’t always work. If the path is straight, use a high-quality rigid scope. If the path is bent or extra long, you’ll either need a fiberscope or a flexible video borescope. The right high-quality borescope makes all the difference.

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