by Svetlana KAMAYEVA, Director General, "Transkor-K" R&D Center; Valerian GOROSHEVSKY, Cand. Sc. (Technology), "Transkor-K" Technical Director; Igor KOLESNIKOV, "Transkor-K" Leading Researcher
Early in 2003 Moscow was the venue of the Sixth International Salon of industrial hardware, "Archimedes 2003". On display were many innovative specimens developed on the basis of our national know-how. One such system enables remote diagnostics of utility and gas-distribution networks-its technology was suggested by the "Transkor-K" R&D Center of Moscow.
Pipelines are an essential part of many industries, be it gas or oil mining, power supply or the utilities. Clearly, this equipment should be safe and reliable. By American estimates, breakdowns on such networks in the United States amount to 3 percent of the GNP, directly. As to indirect costs - involved in trouble-shooting and commercial losses - these are much higher. But health hazards are the worst thing, and that's why it is all-important to preclude failures imperiling people's health and their very life.
It's a gospel truth: better prevent a disaster than repair its damages and losses, often irrecoverable. So the diagnostics of pipelines is a must. They should be fail-safe. This is done by means of inner examination so as to detect flaws, if any, and get them repaired. However, it is often rather hard to apply conventional techniques, especially in urban conditions. First, because flaw detectors may not fit the pipe diameter; and second, because examination of the objects is often not feasible technically-mostly, through the fault of the construction crews.
Economic considerations, too, pose difficulties for prophylactic examination due to prohibitive costs (involved in equipping chambers with diagnostic gear sent down into old pipelines for inspection; in pipe cleaning; in running the calibrator gear, etc.). Elimination of waste after the examination work is also costly enough, too.
But the new techniques developed by "Transkor-K" research scientists and engineers allow to cope with the above difficulties. This technology draws on the results of the work done over many years in magnetometry by experts of the All-Russia Research Institute involved with the construction of pipelines and enterprises of the fuel-and- power complex; by the Moscow Power Institute; and by the All-Russia Research Institute of the Gas Industry. All these research centers pooled efforts. Their findings in the field of metal structure, in magneto-elastic effect * phenomena and in magnetoelastic hysteresis ** made it
* Change of a body's magnetization as a result of deformation. - Ed.
** Magnetization lag versus changes in the magnetic and electric fields. - Ed .
Magnetogram of a gas pipeline section showing metal flaws caused by stress-corrosion cracking before failure. Right, the consequences.
possible to explain the effect of residual magnetization * of metal under mechanical stresses in the external (applied) magnetic field (of the earth in our case) and edge dislocations ** as well as to pinpoint the "danger zones" of possible defects.
We assess the interdependence of these phenomena: concentration of the earth's magnetic field tension and change of polarity within the field's components. Our new- generation magnetometers in the SKIP series allow to detect changes in the charge sign without opening a pipeline. These devices scan the magnetic field both along and across the pipeline's axis. Such diagnostic techniques are highly effective even for pipes lying at a distance of fifteen pipe diameters. And the depth may be from 21 to 23 meters.
The data thus obtained are memory-stored. Our magnetometers are supplied with high-sensitivity converters upgraded by our experts. We have also taken care of software with filtration algorithms so as to minimize the effect of interfering fields.
Thus equipped, crews can pinpoint defects in the metal while staying on the earth surface. Such defects may be caused by a variety of factors (faulty construction-and- assembly work, corrosion or mechanical damages of the outer and inner walls of pipes, and so forth). Furthermore, our technology enables detection of sites with an enhanced corrosion hazard (insulation damages, failures in the performance of electrolytic cathode protection). A crew of two can scan as much as 15 km of pipe daily. In places difficult of access (say, impassable bogs) scanning is done with the help of cross-country vehicles.
Our scanning technology has been tested at gas-and-oil industry enterprises, and it performed fine. Over 2,000 km of pipelines were examined in 2002 alone. The reliability of flaw detection is quite on a par with the indicators of in-pipe inspection. For instance, the scanning of gas pipelines of the BASH-TRANSGAZ Company by our SKIP MBS-04 detected problem areas with a reliability of 76 percent, as confirmed by subsequent pipe openings. This factor was even higher, 87 percent, for oil pipelines of the TATNEFT Company. "Zero examination", too, proved effective for the gas pipeline of the ALROS Company, where mechanical flaws were detected, for one, in welded joints.
* Residual magnetization occurs if external magnetic field tension is equal to zero. - Ed.
** Dislocations - linear defects of a crystal lattice that interfere with the regular alternation of atomic planes. - Ed.
Biocorrosion of metal (within and outside): a) - stress-corrosion cracking in a medium containing sulfate-reducing bacteria (SRB); b) - corrosion pits in an oil pipeline carrying a water-cut medium with SRB; c) - SRB within a biofilm on metal surface in the corrosion zone.
To boost the reliability of corrosion detection, we turned to people competent in biochemistry and microbiology. Now, what could there be in common between these sciences and the running of gas and oil pipelines? But, as American experts say, up to 75 percent pipeline breakdowns all over the world is due to corrosion caused by microflora colonies on the outer surface of the metal. The damage mechanism is much alike, and here conventional methods of corrosion protection (electrolytic, polymer films, etc.) do not work. This process is catalyzed by hydrogen sulfide concentration under the peeling material.
Research scientists joined forces in developing adequate detection techniques: from the Soil Science Department of M. V. Lomonosov Moscow State University; from the RAS Research Institutes of the Biochemistry and Physiology of Microorganisms, of Physicochemical and Biological Problems of the Soil Science, and of Biological Instrument-Making. Pooling efforts, metal scientists and biologists developed a method of detecting metal corrosion caused by microorganisms. They, the microorganisms, consume substances released in the process of corrosion where a pipeline is damaged. Such kind of flaw detection is enabled by the innovative computer-aided system EKOLOG which registers and interprets the microflora's "orchestra". The authors of this system merited a medal at the 27th International Salon of Inventions (Geneva, 1999).
The suggested diagnostic technique was found to be good in medicine and in the soil science as well. Certainly, it should also help in problem solving elsewhere, namely, in boosting the reliability of underground structures of steel and ferroconcrete. Besides, the high sensitivity of the EKOLOG system and its capacity for self-tuition and database collection make us hopeful that soon it will become possible to control any changes in the life of microorganisms and carry out a quantitative assessment of harmful wastes of obscure origin and composition.
Obviously, one can enhance the prognostication reliability for the technical condition of pipelines by using most different diagnostics.
One such technique is the acoustic method. Corresponding devices are being used with much success at enterprises of the fuel-and-power complex. They help detect sites of minor leakages (leak-proofness damages) and restrictions of pipe flow section caused by corrosive and mechanical depositions, and by air blocks.
The aforementioned flaw detection techniques incorporating achievements in different sciences have one thing in common, and this is the possibility of remote monitoring. All these methods combine into a composite technology that makes use of unique instrumental devices developed by Russia's scientists and engineers.
Illustrations supplied by the authors
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