Retractable Tube Screen Thickness Scanner

1. Current situation and demand

In the process of long-term service, the high-temperature and high-pressure pipes on the heating surface of thermal power boilers are washed by smoke, fly ash, soft water and elevated temperature chemical reaction, resulting in local thinning, wear, blow damage, corrosion and other defects of the pipe wall. A pipe explosion accident can eventually occur due to high pressure and high temperature steam inside the pipe. The economic loss of a burst pipe inside a boiler, which needs to be stopped for emergency repair, is so great that power generation companies attach great importance to effectively reducing and avoiding boiler pipe bursts.

Boiler wall tube screens, which have a large inspection workload, rely on conventional ultrasound thickness gauge detection, grinding, thickness measurement, recording three processes to complete, large personnel costs, and long inspection periods.

In addition, the low-temperature reheater and economizer and other areas are narrow, the tube screen layout is dense, the tube screen can be checked only 2-3 outside the position that the personnel can reach, and the remaining tube screen can only be checked by mechanical means to open the tube screen after the personnel enter the way, which is high cost, low efficiency, and the tube screen is easy to deformation. Many of the parts were not inspected due to restrictions on the maintenance period, posing a great risk to the safe operation of the boiler.

2. The feature and function of retractable tube screen scanner
The retractable tube screen scanner is a handheld inspection equipment specifically designed by our company for thermal power boiler water walls, low temperature reheaters, economizers, and areas with dense tube screens. It allows for anti-wear and explosion-proof inspections in areas where personnel cannot enter. This device effectively enhances detection speed and reduces the need for inspection personnel. It enables quick measurements of tube screen thickness over large areas, as well as visual inspections and creep expansion inspections without the need for grinding. Additionally, it can simultaneously save appearance videos and thickness data for future verification purposes.

(1) Video detection: The front end is equipped with a high-definition image sensor, high-brightness LED lighting, and a real-time high-definition camera. This enables the detection of coking, corrosion, damage, and large cracks on the outer surface of the tube wall. Additionally, it has a function for storing detection data conveniently for later verification.

(2) High-precision detection: The electromagnetic ultrasonic thickness measuring device eliminates the need to apply coupling agent during thickness measurement. It achieves a remarkable accuracy of 0.01mm with a wide range of detection from 1.5mm to 100mm.

(3) Pipeline creep expansion detection: Equipped with high-precision electronic calipers, it allows quick measurement of the outer diameter of pipelines and provides an alarm when pipes exceed the creep expansion standard.

(4) Horizontal movement platform of tube screen: For wear assessment, thickness measurement, creep expansion checks on heating surfaces that require lateral movement mostly; this design utilizes double rows of staggered rollers as a stable rolling structure across pipes without turbulence. With magnets at its bottom effectively adhering to the detection surface, it ensures easy pushing without slipping.

(5) Main performance parameters

Machine thickness: 40mm.

Expansion length: 3 meters.

Device movement: magnetic adsorption tube screen, manual force movement.

Working time: Built-in lithium battery, working time is more than 5 hours.

Display storage: thickness, image display on the same screen, support data one-click saving.

3.The application of retractable tube screen thickness scanner

The current method for inspecting the anti-wear and explosion-proof properties of boiler heating surface pipes involves visual inspection, manual touch, and simple measuring tools. However, due to poor inspection conditions, a large number of inspections, and potential dangers in the inspection area, the accuracy, authenticity, and comprehensiveness of these inspections cannot be verified.

By utilizing a retractable tube screen thickness scanner, real-time storage of test data can be achieved to ensure that each tube's testing process is certified and can be reviewed later on. This provides reliable reference data for subsequent maintenance activities.

Furthermore, the structure of the furnace's tube screen is complex and subjected to harsh environmental conditions with risks associated with working at heights. The detectable areas are limited to those accessible by personnel resulting in many missing parts during inspections. By employing a retractable tube screen thickness scanner, comprehensive inspections of hazardous areas as well as narrow sections can be conducted efficiently while saving time and costs associated with drawing out the entire tube screen.
(1) The inspection of the water wall tube screen is conducted using a retractable tube screen scanner. Due to the large area and high number of water wall tube screens, the inspection workload is substantial. Traditional ultrasonic thickness gauge detection requires grinding before measuring the thickness and recording data, which involves three personnel for single point detection. However, by utilizing a row thickness scanner for horizontal detection, there is no need for grinding as it automatically measures and records thickness data. This significantly improves detection efficiency and effectively reduces the number of inspection personnel required.

(2) The inspection of reheater and economizer is carried out using a retractable tube screen scanner. The layout of reheater and economizer tube screens is compact with small spacing between them, making it impossible for personnel to enter manually. Consequently, only the outer three tubes can be detected manually while others remain undetected or require manual opening before testing can be performed, resulting in low efficiency and high costs. With a retractable screen scanner, quick detection of thickness, swelling, appearance defects etc., can be achieved even when the spacing between tubes exceeds 40mm.

4.Conclusion

The retractable tube screen thickness scanner addresses the issue of restricted access to confined spaces such as low-temperature reheaters, low-temperature superheaters, and economizers, thereby reducing tube explosion accidents in these areas. In water wall inspections, it enables faster inspection speeds with one person able to accomplish the work of three individuals, resulting in a 75% reduction in labor requirements. This significant advancement in anti-wear and explosion-proof inspection technology not only greatly reduces costs and construction time but also provides a robust guarantee for the safe operation of boilers.