Solve Major Challenges of Boiler Tubes with Nondestructive Testing
The non-destructive testing (NDT) procedure is an important component of boiler diagnostics. In the course of its implementation, the correctness of the operation of the equipment is determined and the amount of the residual resource of its use is determined. The implementation of this procedure is carried out in accordance with federal rules and regulations for the specified type of activity.
Detection of defects in boilers of the listed types is carried out using a set of non-destructive testing methods.
With time, for NDT of boiler tubes, the Phased Array Ultrasonic Testing (PAUT) has come out as the best method. The method enables complete analysis that not only decreases the downtime but improves with the preventive measures. The aim of designing the high-speed testing lies in adapting to the challenging setting and small space where most boiler tubes are located.
Table of Contents
Various Challenges of Boiler Tubes
How to choose the right method for non-destructive testing?
The Best Tools for NDT of Boiler Tubes
Non-destructive testing process
Choosing a method for non-destructive testing of boilers
Various Challenges of Boiler Tubes
The offset conditions of the boiler tube may present unique challenges: the high temperature, the welder is usually at a strange angle and may be far from the ground, which requires the same power and nuance. Welders are in their own league for a reason. Consequently, the attempts to estimate defects usually involve the following obstacles:
- Different pipe widths through the similar job
- Less ceiling-clearance
- Interlocking pipes to prevent movement
- Weld cap and additional flat defects
Not just this, the boiler tube also causes electricity for all equipment from the factory to the nuclear power plant. Considering these challenges, inspections of boiler tube welds must reduce service interruptions and maintain uptime.
This is the reason, it is necessary to design inspection technology specifically for the job. Conventional methods like radiography are always useful, besides, they have brought many problems, including health hazards and service interruptions. There are other methods to assure regular services and definitely, safety.
How to choose the right method for non-destructive testing?
Choosing the best way to check your pipeline connections is easy. Only the following factors need to be considered.
- Indicators of the economy and technical properties.
- Features of manufacturing a welded structure.
- The state the surface is in.
- Welded joint in thickness and type.
- The metal itself with the definition of physical properties.
Possibly the most suitable boiler tube inspection method is Phased Array Ultrasonic Testing (PAUT) combined with Time of Flight Diffraction (TOFD). Among the unique systems, technicians and investigators have the coverage needed to assure uniform operation.
The PAUT pulse passes through a pipeline with computer timing considerations. This may pulse multiple beams from different angles concurrently and sequentially, creating a whole cross-section also at odd angles. This ability to detect uneven surfaces (like; welding caps), is particularly beneficial for the inspection of boiler tubes.
The Time-of-flight diffraction intends to weld inspection with longitudinal waves to identify sensors on both surfaces of the weld (particularly circumferential and axial and welds). When the beam is associated with a defect in the weld, it will diffract its power. It presents an actual image of the shape and size of some holes in the weld.
The combination of TOFD and PAUT overcomes several challenges faced by radiography. They can identify maximum types of defects, especially flat defects. It involves insufficient root fusion, insufficient root penetration, weld toe cracks and weld root cracks. It implies that it is difficult to miss any overlooked defects.
With a comparison to radiography, TOFD and PAUT services covers:
- Genuine defect sizing and detection
- Instant feedback
- Limited or no interruption to different activities
We can say that the incorporation of TOFD and PAUT is more helpful when examining the full picture, notably when leveraging the best tools.
The Best Tools for NDT of Boiler Tubes
The most essential equipment for boiler tube testing is the non-segregated PAUT unit. It holds every tool required to set up and deploy detection methods. It is suitable for work, and the size is suitable for use in the harsh settings of boiler tubes.
It is a one-stop shop: a complete mechanism for everything from practice to reporting. Thanks to the combination of TOFD technology and a phased array, investigators can obtain a comprehensive idea of the pipeline.
Coupled with the combination of a low-gap scanner that allows online circular motion with a low-gap wedge and probe, it is easy to use on the pipeline. This allows technicians to get high-speed readings from both sides in less than a minute. Both TOFD and PAUT are designed for fast non-destructive testing, which can decrease downtime.
Dissimilar to radiography, there is no need to stop production through the inspection. High-quality PAUT devices will also have software functions that provide effective workflows. It is simple and easy to access, from settings to reports, and extensive analysis tools. It allows for quicker and more active workflows without interruption by attempting to mine various interfaces from varied tools and instruments.
For hundreds of years, Steam has been powering the world. Through high-level boiler tube testing, electricity can be maintained safely and effectively.
Non-destructive testing process
- chalk or kaolin in liquid form is applied to the welded joint of the pipeline;
- after the applied layer has dried, the dry part is removed;
- kerosene is applied on top of the remaining layer;
- after half an hour you need to check the reverse side of the joint;
- if kerosene smudges are found there, then the seam is defective, if not, the connection is reliable.
Nowadays, substances are added to penetrants that help to more clearly identify the deficiencies of metals. Basically two:
- red pigment;
- luminescent substance.
The first is used when control is carried out during the day with natural lighting of the site. The second night, for which they use ultraviolet lamps.
Choosing a method for non-destructive testing of boilers
Non-destructive testing of a pipeline that is not subjected to severe stress can be carried out in simpler ways: hydraulic or pneumatic. To do this, water or air, respectively, is driven into the line under pressure.
In the first case, non-destructive testing is carried out by determining leaks from the opposite side of the connection, that is, from the outside of the pipes. In the second, foam is additionally used, which is applied to the weld. If it starts to bubble, the defect is present.
Non-destructive testing of pipelines has made it easier to verify the integrity and quality of pipe connections. The use of flaw detection, especially X-ray and ultrasound, has practically brought the probability of detecting welding flaws close to 100%. At the same time, such control allows you to find out where the defect is located, how many of them, what sizes and shapes.
Concluding Remarks
What do you think, is it necessary to apply more sophisticated methods of non-destructive testing of pipelines or is it possible to get by with the supply of water/air into the system?
Let us know in the comment section below. Thanks for reading!
Author Bio:
Mark M. is associated with Accutec NDT. He is a web addict and spends too much time in front of the computer. When he manages to get away for more than 10 minutes, he will read books, travel or shoot photos.