Remote Visual Inspection an Important Part of the NDT Toolbox

]]>Remote visual inspection (RVI) is a non-destructive testing (NDT) technique used for the visual inspection of an object in which the person performing the inspection operates a device remotely. The device can be very simple, like a mirror or binoculars, or complex, like a drone equipped with high-resolution video cameras. The inspections can range from a simple advanced visual view such as: B. a magnification through binoculars, to a very detailed, high-resolution live camera view of a small section of a larger assembly. These types of inspections are primarily used in areas of interest that are otherwise inaccessible, or when the inspection area is simply too dangerous for human access.

RVI seems to be a rather modern technique as it requires “equipment”, but the history of remote visualization predates the industrial revolutions. In fact, natural reflective surfaces like polished rock and a still body of water have been used since the beginning of human life to view things like the sun from a distance.

One of the oldest types of RVI devices still in use today dates back to 1608. Hans Lippershey of the Netherlands, an eyeglass manufacturer, filed a patent for what later became known as a telescope. He was not awarded the patent, but his invention would lead to the first RVIs. The following year, Galileo Galilei brought his design ideas to the telescope and significantly improved its functionality.

The history of Galileo's contributions to science and astronomy is well documented. But have you ever come to the conclusion that these achievements were also the beginnings of an NDT technique? In its simplest form, he merely visually examined objects in space from a distance using his enhancement device. A few decades later, another historical figure, Sir Isaac Newton, enhanced the telescope by adding a reflector to make viewing easier. RVI has some legitimate historical credibility.

We have come a long way since those historic times. Cameras are becoming smaller and smaller, have higher resolution and are becoming cheaper every day. Our ability to stay away also seems to be improving at the same pace. There don't seem to be many things a modern engineering team can't do. In early 2021, we were able to see high-definition video of the descent of the Mars rover Perseverance, which was lowered by a sky crane and landed on another planet nearly 136 million miles from Earth – an amazing feat that would have made Galileo proud . This is just an example of the extreme high end of RVI technology, but it shows us how advanced it has become.

Boroscope inspection of the engine. Source: Weaver NDT

RVIs are conducted across all major industries and provide important information for assessments and research. There are many ways to conduct modern RVI inspections. However, since we focus on quality, most inspection applications for quality purposes are performed using three main types of equipment: endoscopes, unmanned aerial vehicles (UAV), and tracked robots. Each of these can be equipped with cameras, video or laser measuring devices. Each has its advantages under certain conditions and situations.

The most common and widely used remote visual inspection device is the endoscope, also called a borescope in many industries. An endoscope is defined in Merriam-Webster as “an optical device (such as a prism or optical fiber) used to inspect an inaccessible space (such as an engine cylinder).”

These devices are designed to access limited and/or difficult to access areas. They consist of either a rigid or flexible tube with a lens, camera or video device at one end and an eyepiece or digital display at the other end. These two ends are connected by either a purely optical or electrical system. Most of these systems are typically accompanied by a lighting source that provides enhanced brightness and contrast to facilitate viewing. The rigid or flexible endoscopes are usually connected to a photography or videography device. These devices are used in small, confined areas such as aerospace and gas turbine components as well as intricately designed additively manufactured parts. They are also used in many assembled systems where access is limited due to the deliberate interlocking of all components. Similar instruments, so-called endoscopes, are used in the medical field. In many cases the technology is very similar, if not identical.

Another device that is increasingly being used in RVI is the unmanned aerial vehicle (UAV). UAVs are much more commonly referred to as drones and have made advances over the last 15 years or so. These advances have helped drones become an important part of remote inspection for many industries. Drones have been routinely integrated into many inspection protocols conducted at otherwise inaccessible and often dangerous altitudes.

Many of the inspections have so far been carried out using elevators, cranes, rope access and sometimes simple binoculars. A UAV has a fairly broad definition due to many military applications, but in the inspection aspect this definition works well: a flying robot that can be remotely controlled or flown autonomously through software-controlled flight plans in its embedded systems. Like the borescope, the drone can be equipped with cameras, video and other sensors.

Drones are used for many bridges, dams, buildings and stadium inspections. Not only do they eliminate the dangers of these types of inspections, but they often improve inspection resolution and can bring a new level of sensitivity to applications. Drone inspections are becoming increasingly common and will continue to be performed as technology advances.

Inspection drone. Drones have been routinely incorporated into many inspection protocols conducted at otherwise inaccessible altitudes. Source: Weaver NDT

A final important piece of equipment for RVIs is robotic crawlers. Robotic crawlers are used in pipelines, power plants, tanks and other commercial applications. Many industrial pipes and tanks require routine inspections and most of them can only be done with crawlers. A crawler robot is an ideal inspection device when long distances must be covered to carry out an inspection. Such inspection devices work similarly to a remote-controlled car and can be equipped with almost all types of digital media devices. Tracked vehicles are the RVIs of choice for sewer pipes, contaminated areas, volatile gas tanks, and nuclear power plant inspections.

The track is an essential piece of RVI equipment that has provided inspectors with remote access to dangerous and inaccessible areas for decades. They continue to improve with modern technology developments and are expected to drive more and more viable applications in the future.

Remote visual inspection is an important part of the NDT toolbox, providing important inspection data while maintaining safety for operators. The three pieces of equipment discussed – borescopes, UAVs (drones) and robotic crawlers – are among the most commonly used devices in this technology. But there are also other hardware with inspection functions.

Although there will always be technological advances in the future, something as simple as a mirror or lens in a telescope can often be considered as equipment for remote inspections. Just ask Galileo.

Without delving into the full capabilities of force and materials testing equipment, this article is intended to point future buyers in the right direction while providing basic guidelines for making the right decision so that the best supplier is able to meet their current and future testing needs.

Greg Weaver is President of Weaver NDT and ASNT LEVEL III RT #149144. For more information, call (505) 340-5680 or email [email protected] or visit

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