Inspection Robots for Power Plants

Managers of large power plants strive to ensure outage optimization, lifetime extension and outage reduction due to which turbines, generators, pressure lines and boilers undergo risk and condition assessment continuously.

In the past, most of the inspection work was done manually by service specialists, but recently non-destructive testing has opened up a totally new world of options.

Today’s inspection robots are capable of evaluating the condition of critical components in a very short time when compared to humans and also with higher accuracy.

Modern day robots are capable of crawling into the smallest structures and offering video images and measurement data or treat surfaces in environments that have not been accessible to humans thus far.

Another benefit of inspection robots is that they are not sensitive to dirt, heat or any adverse conditions. This ensures safety of people working in these plants.

What is the Product Made of?

Boiler tubes in power plants are made up of hundreds of steel pipes of 63.4 mm diameter and more than 30 m in height. Major defects in boiler tubes include:

• Reduction in tube thickness due to corrosion and abrasion
• Internal pinholes or cracks due to erosion.

Certain types of inspection robots for power plants include:

• Crawling robots – Sangdeok Park et al (2002) described crawling robots for power plant applications in his paper titled ‘Development of Mobile Robot Systems for Automatic diagnosis of Boiler Tubes in Power Plants and Large Size Pipelines’. The crawler robot EMAT is so designed as to move linearly along the longitudinal direction of the tubes and also move transversely and be able to steer to move to the next tube. It is designed to be able to move across the concave and convex surfaces of the tube. Each side of the crawler has four magnetic wheels and two wheels form a track using a wide timing belt. A DC motor drives the tracks via a reduction gear, spur gears and timing belt. The transmitter and receiver of the EMAT are provided with built-in permanent magnets. The permanent magnets fix EMAT to the tube during inspection. While scanning, EMAT moves straight with a constant gap between the tube and the sensor by roller bearings. Also a sensor lifting mechanism is required to detach and attach the sensor to and from the target.

• Mobile Robotic Scanners – Mobile robotic scanners include a scanning mechanism that will enable them to scan pipes for any flaws or defects. They can move semi-autonomously or autonomously through pipes, rotors or vessels to perform visual inspection, non-destructive testing, grabbing, picking, cleaning, and surface treatment.

• Automated Scanners – Automated scanners are designed for automated on-site inspection of specific plant components. The integrated position sensors of the scanner ensure accurate position feedback. Since scanning is automated, inspections are done with minimal user attention based on predefined programs or settings.

How it Works

All inspection robots are equipped with sensors and scanners that help them test the surface and provide images, videos as well as data about the condition of the pipe or surface being tested. These are capable of moving to areas where humans cannot go and they can continuously monitor pipes and tubes and report any defects.

It will be sufficient if that particular spot is repaired rather than a person manually checking the whole pipe and then repairing. The robot signals the person in charge and then repair works are undertaken if a person can reach there or else there are robots that are equipped to do the task.

Carnegie Mellon University Biorobotics Laboratory have demonstrated the industrial inspection applications of a robot that takes the same shape and movement of a snake and looks at how this can be used to inspect power plants:

Video courtesy of Carnegie Mellon University Biorobotics Laboratory

The following video by this laboratory demonstrates deployment of their snake robot into a variety of pipes at the Zwentendorf Nuclear Power Plant in May 2013:

Video courtesy of Carnegie Mellon University Biorobotics Laboratory

Advantages

The key benefits of inspection robots for power plants include the following:

• Robots can scan areas that are inaccessible to humans.
• The process can be done on a continuous basis and whenever there is a flaw or corrosion the robot can be informed.
• Robots take just a fraction of the time to perform inspection when compared to humans.
• They are not sensitive to heat, dirt or any adverse conditions.
• Accuracy of inspection robots is considerably high when compared to humans and the data obtained can be relied upon.

Products on the Market - Advancements

Modular Robot from ALSTOM

The modular robot from ALSTOM Inspection Robotics offers multi-purpose features and performs a number of inspections and cleaning operations.

Various camera equipment and sensors can be attached for non-destructive testing assessments and these can be integrated into the robotic navigation system.

The modular inspection robot includes the control station, the modular robot and software and hardware to inspect large areas easily and quickly.

MagneBike - magnetic wheeled robot for the inspection of power plants. Video courtesy of Autonomous Systems Lab

The features and benefits of the modular robot are listed below:

• It is compact and light weight
• Ensures easy, reliable operation and quick inspection
• Multi-payloads are possible and is suitable for a range of applications
• High precision data acquisition and processing
• Electronic slippage control and automatic positioning
• Programmable scan patterns
• Compact packaging for convenient transportation.

Automated Scanner Series from ALSTOM

The Automated Scanner Series from ALSTOM Inspection Robotics is a product series for automated on-site inspection of certain plant components.

Inspections are performed with minimal user interference based on predefined programs or settings. The operator can perform accurate inspections that can be reproduced and compared after the actual inspection.

These products have an adaptive and flexible design that enables customization to specific inspection requirements of the customer.

The key features of the automated scanners are:

• A range of standard scan patterns and freely programmable paths and interactive (manual) control
• Automated data acquisition and scanning
• Adaptive design based on task requirements and the specimen geometry
• Embedded motor control.

Master Slave Manipulators from CarrsMSM

CarrsMSM has developed the VNE 80 and VNE 90 gas tight master slave manipulator approved by the UK Nuclear Industry to be used in fuel element reprocessing cells and post-irradiation examination laboratories where hermetic sealing for negative or positive pressure is required.

The manipulators are of modular construction and include the extension tube, the master arm, slave arm and through tube. All key assemblies can be interchanged throughout the range of manipulators. The slave arm, master arm and extension tube can be detached from the through tube maintaining containment.

Sources and Further Reading

• Master Slave Manipulator - CarrsMSM

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