Applying New Technology to Visual Weld Inspection By Etienne Berthiaume and Jeffrey Noruk
Hand-held scanners prove useful for visually inspecting welds
Nondestructive examination (NDE) includes a variety of inspection methods. For many types of welds, integrity is verified by visual inspection. In fact, visual inspection is the NDE method used for more than 95% of welds made each day. It is easy to apply, quick, relatively inexpensive and, historically, requires no special equipment. Tools of the trade have included a flashlight, magnifying glass, scales and special gauges.ondestructive examination (NDE) includes a variety of inspection methods. For many types of welds, integrity is verified by visual inspection. In fact, visual inspection is the NDE method used for more than 95% of welds made each day. It is easy to apply, quick, relatively inexpensive and, historically, requires no special equipment. Tools of the trade have included a flashlight, magnifying glass, scales and special gauges.
Fig. 1 -- A hand-hheld joint and weld scanner with control box.
Visual inspection involves more than just looking at a finished weld and declaring whether it is good or bad. The process begins prior to welding by examining joint preparation, alignment and clearances. During welding, the requirements of the Welding Procedure Specification (WPS) must be followed and all requirements must be met. Root pass quality and joint fill are two characteristics that need to be verified. After welding, the completed weld must be measured and compared to the applicable quality standard. Type, location and size of any defects must be noted. Finally, visual inspection is required to verify that any weld defects are repaired properly. One More Tool of the Trade
Visual inspection methods and tools have not changed much over the last 50 years. However, hand-held weld scanners have been added to the variety of tools available for visual inspection ‹ Fig. 1. By aiming an activated scanner at a joint preparation or finished weld, an operator can obtain measurements and validation of geometry against preset thresholds. Such devices can assist in the time-consuming, error-prone and repetitive task of manually inspecting welds with conventional gauges.
Hand-held scanners supply large amounts of data via visual displays, computer-saved records and strip chart printouts. Typical features measured on a prepared joint include root opening, included angle, material thickness and root face size ‹ Fig. 2. For the finished weld, features such as leg length, weld length, skips, toe angle, concavity/convexity and undercut can be directly measured. In addition, for both preweld joints and finished welds, information about actual joint volume to be filled, throat size (theoretical), off-joint amount and percent over- welding can be calculated.
Pros and Cons
Hand-held scanners facilitate the repeatability of the visual inspection process by making actual measurements less subjective, i.e., less sensitive to different inspectors, lighting conditions and incorrect interpretation of welding codes when correct code thresholds are entered into the computer prior to inspection.
Fig. 2 -- Scanner display on a Palm IIIc.
A permanent record is produced similar to that available with radiographic or ultrasonic testing. Inspection data can be saved to a computer file and/or printed out on a strip chart that represents the length of the weld inspected. This permanent record can be used to develop trending information (i.e., what welds are experiencing the most problems, which welder is producing the most defects and what is the parts per million defect rate). A permanent record can also provide exact defect location to help expedite repairs. This will enable users to meet standards like ISO 9000, ASME and AWS, which require documentation be kept on file for a number of years.nondestructive examination (NDE) includes a variety of inspection methods. For many types of welds, integrity is verified by visual inspection. In fact, visual inspection is the NDE method used for more than 95% of welds made each day. It is easy to apply, quick, relatively inexpensive and, historically, requires no special equipment. Tools of the trade have included a flashlight, magnifying glass, scales and special gauges. Visual inspection involves more than just looking at a finished weld and declaring whether it is good or bad. The process begins prior to welding by examining joint preparation, alignment and clearances. During welding, the requirements of the Welding Procedure Specification (WPS) must be followed and all requirements must be met. Root pass quality and joint fill are two characteristics that need to be verified. After welding, the completed weld must be measured and compared to the applicable quality standard. Type, location and size of any defects must be noted. Finally, visual inspection is required to verify that any weld defects are repaired properly.
One More Tool of the Trade
Visual inspection methods and tools have not changed much over the last 50 years. However, hand-held weld scanners have been added to the variety of tools available for visual inspection ‹ Fig. 1. By aiming an activated scanner at a joint preparation or finished weld, an operator can obtain measurements and validation of geometry against preset thresholds. Such devices can assist in the time-consuming, error-prone and repetitive task of manually inspecting welds with conventional gauges.
Hand-held scanners supply large amounts of data via visual displays, computer-saved records and strip chart printouts. Typical features measured on a prepared joint include root opening, included angle, material thickness and root face size ‹ Fig. 2. For the finished weld, features such as leg length, weld length, skips, toe angle, concavity/convexity and undercut can be directly measured. In addition, for both preweld joints and finished welds, information about actual joint volume to be filled, throat size (theoretical), off-joint amount and percent over- welding can be calculated.
Pros and Cons
Hand-held scanners facilitate the repeatability of the visual inspection process by making actual measurements less subjective, i.e., less sensitive to different inspectors, lighting conditions and incorrect interpretation of welding codes when correct code thresholds are entered into the computer prior to inspection.
A permanent record is produced similar to that available with radiographic or ultrasonic testing. Inspection data can be saved to a computer file and/or printed out on a strip chart that represents the length of the weld inspected. This permanent record can be used to develop trending information (i.e., what welds are experiencing the most problems, which welder is producing the most defects and what is the parts per million defect rate). A permanent record can also provide exact defect location to help expedite repairs. This will enable users to meet standards like ISO 9000, ASME and AWS, which require documentation be kept on file for a number of years.
The preweld and interpass inspection can be used to help ensure the procedure is being followed correctly. It can also assist the welder in changing the parameters to compensate for unanticipated variation. This could be helpful in mechanized and automated operations where the preset values of current and travel speed to get the proper fill rate to maintain weld bead sequence can be changed.
Information gathered from such devices can help reduce overwelding, which can save money and reduce distortion. Studies have found that a typical manual welder who produces welds just 1 mm over size can cost a company more than $10,000 per year. Scanners can be used to get the joint right before welding and also to provide feedback about how much overwelding is occurring. Of course, no device is right for everyone. Hand-held weld scanners may not fit into every area to be inspected. The cost is more than typical gauges, which may be limiting for small companies or ones that do not do much welding. Prices may, however, go down as computer and vision technology improves.
The preweld and interpass inspection can be used to help ensure the procedure is being followed correctly. It can also assist the welder in changing the parameters to compensate for unanticipated variation. This could be helpful in mechanized and automated operations where the preset values of current and travel speed to get the proper fill rate to maintain weld bead sequence can be changed. Information gathered from such devices can help reduce over welding, which can save money and reduce distortion. Studies have found that a typical manual welder who produces welds just 1 mm over size can cost a company more than $10,000 per year. Scanners can be used to get the joint right before welding and also to provide feedback about how much over-welding is occurring. Of course, no device is right for everyone. Hand-held weld scanners may not fit into every area to be inspected. The cost is more than typical gauges, which may be limiting for small companies or ones that do not do much welding. Prices may, however, go down as computer and vision technology improves.