4 Effective Methods for Inspecting Carbon Steel Tubing
Carbon steel tubing is frequently found in boilers and heat exchangers. They are commonplace and frequently used in the following industries:
- Power generation stations
- Petrochemical plants
- Petroleum refineries
- Natural gas processing plants
Due to the nature of its use and environment, carbon steel tubing is subjected to a lot of environmental damage and stress. These are some of the Issues that can occur with carbon steel tubing in boilers and heat exchangers:
- Corrosion: This is often caused by water, steam, chemicals or oxygen moving through the tubing. This can manifest itself as loss of wall and degradation on the inside and outside of the tube wall.
- Creep Damage: This is a metallurgical change in boiler tube material caused by high heat flux and environmental stress.
- Thermal fatigue cracking: These are external, transverse cracks that form in colonies because of the strains of expansion and contraction due to temperature fluctuations.
- Chemical corrosion: This occurs when chemicals gradually wear down the wall thickness of a boiler tube. An example is chelant corrosion (caused when a chelant is used as an oxygen scavenger in boiler feed water)
- Pinhole leaks: Small holes can occur in tubing due to corrosion when a corrosion pit penetrates the wall it can cause leaks.
- Baffle wear: This is mechanical damage caused in heat exchanger tubes caused by vibrating inside support plates.
- Carbon dioxide corrosion: This is usually present on the external walls of heat exchanger tubes found in refineries and gas plants.
- Oxygen pitting: This damage is generally found on the outer diameter of fire-tube boilers.
- De-alloying: Most commonly found in brass condenser tubes, which lose their zinc over time due to chemicals used for oxygen control (chelants.)
How Can Russell NDE Help?
Russell NDE recognizes that the inspection and monitoring of carbon steel tubing is extremely important. It can be very inconvenient and expensive when exchangers and boilers fail, causing plant shutdowns and loss of production.
- Our company has decades of experience in conducting NDT inspections of carbon steel tubing.
- We can help your company select the most appropriate NDT techniques to inspect your heat exchangers and boilers.
- We lead the industry in the development of technology for heat exchangers and boilers
- Russell NDE can minimize the downtime of heat exchangers or boilers during inspections.
- Our company can help you to come up with a maintenance plan and the NDT inspection program of heat exchangers and boilers.
Russell NDE was the first company (back in 1988) to offer a commercial instrument using the Remote Field Technology (RFT) technique for heat exchanger tube inspection. Our company has led the industry with innovative products and since then many eddy current instrument manufacturers (such as Olympus, CoreStar, Eddy Current Technologies, Zetec and Eddy-Fi) have added RFT capability to instruments.
What Technologies Does Russell NDE Utilize for Carbon Steel Tubing Analysis?
Russell NDE uses the most advanced methods when inspecting carbon steel tubing in boilers and heat exchangers to cut down the time it takes to analyze the pipes. A large variety of NDT methods are available for the condition assessment of heat exchanger and boiler components. Our company can help you decide the best NDT technique for the job based on:
- the type of components in the heat exchanger or boiler,
- the type of defects that may be present,
- the specific needs of the company in terms of amount of downtime they can tolerate, how invasive the inspection can be, and
- the accessibility and cleanliness of the tubes.
There are four main technologies used for the inspection of steel tubing which use internal probes travelling through the length of the tube.
- Saturation Eddy Current: Carbon steel tubing has a high relative permeability that constrains technicians from using regular eddy current probes because the eddy currents aren't able to penetrate the tubing. The difference with saturation eddy current is that the probe contains a permanent magnet to reduce the relative magnetic permeability of carbon steel tubes so that regular eddy current coils can interrogate the tube. Russell's Ferroscope 308 has won multiple awards for this innovative tool and it is extremely effective at detecting pits, pin holes, and wall loss in heat exchangers and boilers. It can be utilized on magnetic and non-magnetic materials with a diameter of 0.25" (6.35 mm) to 3.5” (88.9mm) with wall thickness up to 0.200" (5.0 mm).
- Remote Field Technologies (RFT): This NDT technique operates through the physics of electromagnetics to find defects in the walls of carbon steel tubing. RFT probes consist of one or two transmitter coils (exciters) which send a signal to one or more receiver (detector) coils. The transmitter/exciter coil emits a low frequency electromagnetic field. The field created by the transmitter/exciter coils travels along and through the pipe wall and is picked up by the receiver/detector coils. The data collected can reveal erosion, corrosion, wall thinning, and baffle wear that degrade tube performance. RFT is the fastest and most reliable inspection technique for carbon steel tubes. Russell NDE is very experienced in using this technology (as we have been utilizing and developing it since the late 1980's.) We also have accessories that automate the inspection of boiler wall tubes such us our VertiScan System and Wall Crawler,
- Internal Rotary Inspection System (IRIS): IRIS technology inspects carbon steel tubing by sending out an ultrasound pulse from a focused ultrasonic transducer through a rotating 45 degree mirror. The mirror bends the ultrasound by 90 degrees. As the mirror rotates, ultrasonic thickness readings are taken and displayed at a rate of up to 360 readings per rotation and the echoes are then interpreted by custom software. An IRIS probe is inserted into a tube that is filled with water and the ultrasonic beam allows detection of metal loss on the inside and outside of the tube wall. The probe is moved through the tube as the software collects data to determine the thickness of the tube walls and pinpoint weak spots caused by erosion and pitting. IRIS is the gold standard for precision, with an accuracy exceeding +/-0.002". This method can inspect almost any metal or plastic tubing.
- Magnetic Flux Leakage (MFL): This NDT approach is the quickest of all the four techniques discussed. It uses magnetism to saturate the tube wall and magnetize the steel. It can find leaks, cracks, corroded areas, pitting, and measures the wall thickness of carbon steel tubing. This method converts changes in the magnetic field that are detected by hall-effect sensors or coils in the probes and displays them in the computer software as changes in amplitude on a graph. It should be mentioned that this method can lack accuracy because pits of different diameters (same depth) can give very different amplitude responses.
If your company uses heat exchangers or boilers with carbon steel tubing, Russell NDE has the expertise and technology to inspect these devices. Contact us at 1 (800) 661-0127 or by e-mail at firstname.lastname@example.org to hire us for your next inspection