Boiler Tube Inspections
Generating Banks: for generating banks in drum-to-drum boilers, we use the TesTex Eagle 2000 RFET System to perform full-length tube inspections that detect and quantify flaws in both straight and bend sections. We can conduct these tests from mud drums (with CL to CL < 25 feet) or steam drums. Furnace or Waterwall Tubes: for furnace or waterwall tubes in larger industrial & utility boilers, we detects ID or OD flaws on the hot-side the tube, too. To gain access to these areas, we work from hard scaffolding or swing staging.
Gas, Oil and Coal-burning Boilers: for gas-burning and most oil-burning boilers, no surface preparation prior to testing, and for coal-burning boilers, a quality high-pressure water blast is frequently all that is needed.
Waterwalls, Super Heaters and Reheaters: To inspect waterwalls, super heaters and reheaters, we use the TesTex TS-2000 Tube Scanning system based on the Low Frequency Electromagnetic Technique (LFET). From the OD, LFET technology scans approximately 120 degrees of the tube circumference with a single pass of the scanner. Any flaw indications (or areas that we cannot scan due to tube bends, welds, viewports, etc.) are proved-up using A-Scan ultrasonics.
New Boiler Tube Inspection Applications:
- Thermal Fatigue Cracking
- Corrosion Fatigue Cracking
- Magnetite Detection
Comparison to Alternative Methods
For generating banks:
Three other methods are used to inspect of generating banks in drum-to-drum boilers:
- Spot Check Ultrasound
- IRIS Ultrasonic Testing
- ID Laser Profiling (LOTUS)
Traditional Spot Check Ultrasound is performed from the OD (fireside) of the tubes, and is generally limited to areas that a person can access, or “put his hands on,” which provides very limited coverage and leaves a large percentage of surface area untested.
The IRIS Ultrasonic Testing method is conducted from the tube’s ID and is generally conducted from the boiler steam drum. IRIS can be conducted from the mud drum, but it is very difficult to perform due to the use of water as the couplant for ultrasound.
The IRIS UT Testing method is good for detecting and quantifying flaws in the straight or vertical sections of the generating bank but not for tube bends. While the IRIS UT Testing method is good, it requires that the tubes be very clean on the ID and is slow to perform, i.e., approximately 100 – 200 tubes can tested in a single ten – twelve hour shift versus 300 – 400 tube with our NDT.
The LOTUS method of ID Laser profiling is a very effective method for any detecting and quantifying flaws on the inner diameter of a given boiler tube, however, the tubes have to be cleaned so that the laser is reading the base metal; there can be no scale or deposits. As importantly, only ID flaws are detected by laser profiling. The LOTUS method is not applicable for any type of OD flaws.
TesTex does offer IRIS Ultrasonic Testing as well as video borescoping and spot-check UT for boiler generating banks, however, we prefer to recommend our LFET and RFET.
For Boiler Waterwalls
Besides the TesTex LFET, there are at least four other ways to inspect of boiler waterwalls:
- Spot Check Ultrasound
- A-Scan Ultrasound (UT)
- Scanning Thermograpy
Spot Check UT only provides thickness readings and gives very minimal coverage of the total surface area of the furnace waterwalls; so, the chance of finding ID flaws are low at best. If the boiler waterwall was sandblasted, A-Scan UT may be used to inspected larger areas of the furnace walls; in these cases, a steady flow of water is most often used as the couplant.
The EMAT technique requires that any Boiler Waterwall surfaces be sandblasted and does not provide good coverage unless multiple passes are performed.
Scanning Thermography is the most recent development for the inspection of boiler waterwalls; however, it is not yet commercially available in enough capacity to address the needs of the U.S. power industry.
Corrosion Fatigue Cracking: For boiler tubes experiencing Corrosion Fatigue Cracking, TesTex uses the Balanced Field Electromagnetic Technique to measure the depth of the cracking. The location of the corrosion fatigue cracking and the boiler design dictates the type of probes to use. TesTex can either examine the tubes from the outside diameter or by inserting a probe on the inside of the tube. We have worked with clients to design customized probes for the inspection of their boiler tubes. Please follow this link for additional information on our capabilities.
The TesTex Advantage
To test for corrosion in boiler generating bank tubing within a few inches of the mud drum or steam drum, TesTex offers near drum inspection via its Octavision Near Drum Inspection Tool. This unit provides a high-resolution test of the first four-to-six inches of tubing near the drums.
- Inspects straight sections and bends
- 300 – 400 generating bank tubes can be inspected using RFET in a single ten-hour shift
- 2,000 – 3,000 linear feet can be scanned using LFET in a single ten-hour shift
- TesTex can field more than 40 inspection crews at any given time
- TesTex inspection crews are equipped with multiple scanner/probe sizes and back-up equipment so that there are no delays on our part
- Neither RFET nor LFET require extensive tube cleaning
- Can inspect tubing from with diameters one-half inch and greater
- Both TesTex RFET and LFET get more area coverage than the other respective techniques
- All data is stored for future reference
We also inspect tubular air heaters when present on certain boilers.