Automated Ultrasonic Inspection Device

Issue: The current implementation of pitting inspection is rather tedious and prone to error. Operators are required to inspect multiple areas of concern (12”x12”) on their hands and knees using a small probe (1”x1”) which as a result depends on the operator’s skill to accurately assess the associated risk levels. Therefore, it is possible for undetected pits to remain at risk and avoid repair.

Solution: By introducing two stepper motors, the device is capable of scanning the entire area. One motor sweeps the scanning probe along the full width of the desired area while the other motor moves the driving wheels forward at increments between probe sweeps. The combined movement will produce a serpentine path to ensure the floor is fully covered with minimal operator input.

Issue: Current commercial variations of automated ultrasonic inspection devices generally require a fully integrated set of equipment which is extremely costly at typically $40,000 – $50,000 per unit. If a single piece of equipment malfunctions, it is possible for the device to become nonfunctional. Furthermore, Nextgen already has invested tens of thousands of dollars in ultrasonic equipment that would be incompatible with commercial options, thus making it essentially useless if moving to all automated inspections.  

Solution: To overcome this problem, our device is universally compatible with various ultrasonic equipment and consists mainly of off the shelf components that can easily be obtained at local stores and major online distributors. Having a generic frame allows Nextgen to use their current equipment and automate their inspection process for a far smaller investment compared to commercial options. This also makes maintenance quick with replacement parts easily available and allows for future upgrading with new equipment or parts. 

Issue: Operators are limited in their ability to record inspections in a digital format to provide to customers. The current process involves finding the thinnest spots and marking down the values by writing on the floor itself. As a result, there is no current way to provide a historical record of the entire plate section that is easy to reference in the event of future inspections.

Solution: By using our Raspberry Pi, the data collected during the scanning process is saved to a CSV file in real time. The file is then used to populate a heat map that illustrates key points of risk within the area of concern. This process provides easily readable and accessible data collection for both users and clients to understand the entire thickness of the area scanned. 

Due to the variety of pre-existing ultrasonic equipment available, our device has incorporated several design choices to integrate universal compatibility with a variety of ultrasonic scopes. This will allow operators to use the inspection device regardless of the equipment they currently possess at a significantly lower cost compared to commercial options. Furthermore, maintenance and future upgrading will be easier with greater interchangeability. 

The automated inspection device incorporates a graphical user interface (GUI) to assist the operator in scanning operations with adjustable features. These features include custom scanning dimensions, the choice of imperial or metric units, and the ability to pre-name data file names. In addition, the GUI provides a visual representation of the heat map which reflects the data collected from the scope. This heat map can be easily understood by clients and provides stored quantitative values for the whole area scanned, unlike the current method of writing the thinnest measurements on the floor by hand.

After receiving the prescribed inputs from the operator, the device is capable of independently completing the scanning process without further guidance. This allows the operator to manage multiple devices at a single instance and as a result, will reduce the overall inspection time for storage tanks and allow operators to complete inspection tasks with a higher level of efficiency. Using the current prototype, three devices operating at the same time in separate locations is the breakeven point compared to a single operator manually scanning by hand. 

The decision to build the automated inspection device using simple off the shelf components makes the device cost-effective and easy to manufacture even with limited machining capability. Basic shop tools like an angle grinder, drill, and hacksaw can be used to create the frame. As such, dozens of our devices could be made for the cost of one commercial scanner, making an effective fleet of automated devices that would greatly shorten overall inspection time.

As current inspection methods involve the inspector to go on their hands and knees, our device eliminates that need and includes several ergonomic features that will assist operators in the field. The combination of aluminium rails and steel handles, make the device relatively lightweight (approximately 10 lbs) and easy to manage when traversing between locations. In the case of an emergency, an emergency stop-button has been added to halt all functions of the device.

Through our testing methods of the final prototype, it is proven that our design provides speed improvements when using three or more devices for each operator. Furthermore, the device is sufficiently accurate in compliance with API 653, with the heat map determining actual pit locations within ½” in the X-Y direction and remaining metal thickness within 0.001”. Also our device is reasonably durable to survive a full day of inspections, with minimal maintenance over 200 scans, and is operational in a variety of seasonal temperatures.

Our prototype met all the design requirements established by the problems facing Nextgen and provides a more operator friendly device while being under the budget of $2000.

• Due to the teams decision to use easily available components of relatively low cost, a single device can be built for approximately $1200; a large decrease from the proprietary cost of $50,000. This provides motivation to build several devices as parts are low cost, easily accessible, and will decrease inspection times due to the automated nature of the device. 

• The completion of the first device has minimized the build times for future devices as many steps of the initial prototype have been completed. This includes the software to operate the device, custom part designs for assembly and a custom printed circuit board for the wiring of the device. As a result, a fully operational device can be completed in approximately 2 to 3 days (first device took approximately 6 working days). It could be further improved by utilizing more efficient manufacturing processes such as plasma cutting or waterjet cutting. 

• Lastly, the device can be easily upgraded over time due to the simple parts and build process. This provides a longer work life for the device as it can be easily maintained/altered to reflect future iterations. This establishes further incentive to use this device over proprietary equipment that costs thousands of dollars to update to a new generation.