TesTex can provide numerous options for the inspection of Heat Exchangers; RFET (Remote Field Electromagnetic Technique) Eddy Current, IRIS and Remote Visual Inspection.
The Eagle Plus RFET System is commonly used to test carbon steel tubing. A probe is inserted into the tube at one end and pushed through the length of the tube. Data is collected onto a laptop computer as the probe is withdrawn from the tube at a steady rate. Typical defects found are general corrosion/erosion, gross pitting and baffle cutting (support plate fretting). The Eagle Plus System uses no magnets or couplant and is capable of testing upto 300 tubes in one shift with one system. Sizes of tubes tested range from 0.5" to 6.0" O.D.
For an even more detailed inspection of tubes, TesTex uses the ultrasonic IRIS system for ferrous materials. This inspection will detail internal and external corrosion/erosion and pitting as well as remaining wall thickness. The equipment does require a water couplant and very clean tubes. Typically 50 - 120 tubes may be inspected in one day of inspection, with reports detailing the condition in each tube.
TesTex also utilises the latest in standard Eddy Current Technology (ECT) to provide fast, accurate and cost–effective non-ferrous tubular inspections. The TX4400 is our 4-frequency conventional Eddy Current system. It is DSP based and controlled by a laptop computer. Both absolute and differential data is collected with filtered and mixing capability for suppressing support plates and baffles.
For larger jobs, the TesTex Ultra High Speed ECT System can inspect up to eight tubes per minute using probe pushers/pullers. Data is collected and defect sizing is automated through proprietary software analysis tools.
We have different types of RVI cameras to supplement the above inspections and also check for internal defects, shell side condition (where access allows) general tube cleanliness and blockages.
Results can be presented in a format specified by the customer. Plugging criteria and a full report with colour-coded tube sheet map is standard.
| In just one day TesTex had completed the inspection of 316 condenser tubes |
From the Field – May 2004 A chemical plant in the UK were having problems cleaning & testing the tubes of small condenser units. TesTex were on site to perform IRIS inspection but due to the inadequate cleanliness of the tubes (a common problem), the IRIS technique was ineffective. It was suggested to the client that Remote Field Electromagnetic Technique (RFET) was performed on the tubes. The unit consisted of 466 x 1” c/s tubes. In one day TesTex completed the inspection of 316 tubes (68% inspection)
The majority of the tubes tested showed very little evidence of pitting or general wall losses, however, a number of tubes displayed signs of severe wall loss at two of the baffle area’s.
23 tubes tested showed wall losses greater than 31%. The ‘worst’ tube showed 51-60% wall loss (based on the nominal wall thickness of 0.140”) After the work was completed, one of the tubes was pulled for visual examination. This confirmed the wall losses reported by our technicians, as such TesTex inspected the remaining 150 tubes the following week and reported wall losses greater than 31% on a further 32 tubes.
Fig.1 – RFET data collected from the worst tube. Shows 51-60% wall loss (circled on right) Also note that 41-50% wall loss was also found (circled on left)
Fig.2 – Photograph of the pulled tube confirming the 51-60% wall loss.
Conclusions: TesTex can provide RFET, IRIS, Eddy Current and Remote Visual services for the inspection of heat exchanger tubing. Having the ability to adapt to different circumstances, even whilst on site, is one of the many advantages of our ‘multi technique’ approach. The client was particularly pleased as we now inspecting identical units without the need of HP jetting; saving critical downtime and obvious costs.