The Totals of Application of the Metal Magnetic Memory Method to Industry in Russia and Other Countries

Dr., Professor A. A. Dubov

The metal magnetic memory method (MMM) is the non-destructive testing method based on the analysis of self-magnetic leakage fields (SMLF) distribution on components’ surface, and is intended for determination of stress concentration zones, imperfections, heterogeneity of metal structure and welded joints.

Based on the established correlation of dislocation processes with the magnetic phenomena physics in products’ metals the concept "metal magnetic memory" was introduced and a new diagnostic method was developed. The uniqueness of the metal magnetic memory is that it is based using of the self-leakage magnetic field (SLMF). Occurrence of SLMF is caused by formation of domain boundaries at accumulation of high-density dislocations (dislocation walls). Obtaining of such an information source like self-leakage magnetic field is not possible in any conditions with artificial magnetization. Such information is formed and can be obtained only in a weak external field like the Earth’s magnetic field in loaded structures, when the strain energy exceeds the external magnetic field energy by order. It was demonstrated in practical works that MMM can be applied both at equipment operation and after working unloading, during the repairs. Magnetic texture, formed under the action of working loads, becomes, so to say, "frozen" after unloading by virtue of the "magnetic dislocation hysteresis". Thus, there is a unique opportunity to perform assessment of equipment’s stress-strained state and detect zones of metal maximum damaging by reading this information using specialized instruments.

Interest of experts of Russia and other countries from various industries to essentially new magnetic method of non-destructive testing (NDT) grows steadily. Application of the MMM method and corresponding inspection devices to industry, as a rule, is carried out on a voluntary basis that is vivid confirmation of the method efficiency.

Interest to the method is caused by unsolved problems, which arise in practice at quality control of engineering products, at reliability control and at equipment life estimation.

Let’s denote the basic from them.

• Till now on the majority of manufacturing plants in Russia and other countries there are no 100% quality control of production on heterogeneity of metal structure. Due to this reason the spread of mechanical properties on new products reaches 20% and more, that considerably reduces their lifetime.

• Welding exists more than 100 years, and NDT methods, which allow in practice to carry out express quality control of welded joints in the united complex system of the factors "structural-mechanical inhomogeneity – defects of a weld – structural and technological stress concentrator", till now are not present. Now non-destructive test is commonly applied with detection of inadmissible defects (at that, the scientifically-grounded norms for the sizes of permissible defects in welded joints from the point of view of fracture mechanics, as a rule, are not present). The most important – distribution of the residual welding stresses determining welded joint reliability till now is not examined.

• Existing problems of a lifetime estimation of the aging equipment with usage of conventional methods and control devices are not solved because of their unfitness for early diagnostics of fatigue damages.

It is possible to speak confidently, that if we have the old equipment, which we cannot 100% inspect on metal structural damaging and detect imminent damages; in this case we work on sudden failure.

Thus, in spite of the fact that non-destructive testing exists in Russia and other countries already more than 100 years, many problems of products quality control and diagnostics are still unsolved. Therefore demand of the MMM method directed on the solution of specified NDT problems, is caused by daily practice and a life of the enterprises.

The method of metal magnetic memory under the physical substance represents not only essentially new NDT magnetic method, the method is a new trend in engineering diagnostics as it unites potentials of non-destructive testing, fracture mechanics and materials science.

The following guidance documents based on the method of metal magnetic memory are developed and applied nowadays in power engineering, petrochemical, gas production and other industries in Russia:

• GD 10-577-03. Standard instruction for metal control and lifetime prolongation of boilers, turbines and pipelines main units at thermal power stations.

• GD 34.17.446-97. Technical guideline for engineering diagnostics of heating surface pipes of steam and hot-water boilers.

• GD 34.17.437-95. Technical guideline for engineering diagnostics of welded joints on pipelines and vessels (temporary document).

• GD 51-1-98. The technique for on-line computer diagnostics of local gas pipeline segments using the metal magnetic memory.

• GD 03-380-00. The instruction for inspection of ball vessels and gasholders for pressurized liquefied gases storage.

• GD 03-410-01. The instruction for complex engineering examination of isothermal vessels for liquefied gases.

• GD 12-411-01. The instruction for diagnostics of gas pipelines underground networks.

• GD 102-008-2002. The instruction for diagnostics of pipelines technical condition by non-contact method.

• GD 153-39.4-053-00. The technique for gates condition diagnostics during operation before and after overhaul using NDT methods.

• GD 08.00-29.13.00-KTN-012-1-05. The regulations for procedure of engineering examination and lifetime prolongation of oil pipelines fitting.

• GD 16.01-60.00-KTN-085-1-05. The technique for diagnostics and certification of the ODS technological oil pipelines.

• MR-10-72-04. Methodical recommendations for technical condition assessment and residual life estimation in order to determine the possibility to prolong elevators safe operation life.

The techniques and methodical guidelines developed by Energodiagnostika Co. Ltd and agreed with State Engineering Supervision of Russia (Rostechnadzor):

• Technical guideline for engineering diagnostics of pipelines.

• Technical guideline for engineering diagnostics of vessels and apparatuses.

• The technique for assessment of steam boiler drums condition.

• The technique for assessment of boiler and steampipe bends condition.

• Technical guideline for magnetic inspection of elevators metallic structures.

• Technical guideline for engineering diagnostics of electrical rotary pump systems (ERPS) end parts.

The techniques and methodical guidelines developed by Energodiagnostika Co. Ltd:

• The technique for assessment of steam turbine rotors condition.

• The technique for assessment of steam turbine blades condition.

• The technique for control of turbine rotors flushing holes.

• The technique for assessment of individual parts condition in turbine equipment (studs, bearing inserts, etc.).

• The technique for assessment of turbine bodies, cylinders, lock and control valves condition.

• The technique for assessment of generator sleeve tubes condition.

• The technique for assessment of compressor system blades and rotors condition.

• The technique for control of babbit abutment density on sliding bearing inserts.

• The technique for detecting mechanical stress concentration zones in gear wheels.

• The technique for control of crane pivots, buckets, hooks and hook hangers.

• Technical guideline for engineering diagnostics of compressor-boring pipes and couplings.

• Technical guideline for in-pipe diagnostics of heat exchangers.

• The technique for control of production trees at oil and gas fields.

• Technical guideline for non-invasive magnetometric inspection of gas and oil pipelines using TSC-type devices.

• Technical guideline for inspection of large-diameter pipelines (?530-1420mm) using specialized scanning devices and the MMM method.

• Technical guideline for inspection of rolling-mill working and back-up rolls.

• Technical guideline for ?2,0 and ?2,6 steel wire inspection.

• Technical guideline for inspection of locomotive power components (frog, shaft, spline joints).

• The technique for control of stress distribution in tightened bolted joints.

• The methodical guidelines for engineering diagnostics of high-voltage line derrick guys fastening units.

• The technique for detection of mechanical stress concentration zones in products and equipment.

Energodiagnostika Co. Ltd has developed and produces on a full-scale basis the following specialized inspection instruments and the appropriate program software:

• Tester of Stress Concentration Magnetometric TSCM-2FM and advanced TSCM-2FM.

• Electromagnetic Indicator of Cracks EMIC-1M, EMIC-2M.

• Testers of Stress Concentration with scanners on the basis of microprocessor: TSC-1M-4, TSC-2M-8, TSC-3M-12 and TSC-4M-16.

• Tester of Stress Concentration on the basis of Notebook TSC-5M with 32-channels scanner.

• The"MMM-System" software for computer processing of MMM-inspection results using Windows’XP/Vista.

• The "MMM-Lifetime" software.

The instruments are certificated in Gosstandard of Russia and are included in the State List of Measuring Instruments. Certificates RU.C.37.003.A No.9192 and No.9193.

In 2002 the standard of the Russian Welding Society ST RWS 004-03 "Non-destructive testing. Welded joints of equipment and constructions. Method of metal magnetic memory" was approved.

Three Russian standards are published:

• GOST R 52005-2003. Non-destructive testing. Metal magnetic memory method. General requirements.

• GOST R 52081-2003. Non-destructive testing. Metal magnetic memory method. Terms and definitions.

• GOST R 52330-2005. Non-destructive testing. Stressed-strained state test on industrial objects and transport. General requirements.

Since 1998 the Russian and International Center for experts training and certification by the method of metal magnetic memory with issuing of Level I and II Certificates operates in Moscow. The branches of the center operate in Warsaw and Beijing. As of 2008, more than 1300 experts in Russia, more than 250 experts in China and 70 experts in Poland passed training.

The first, second, third and fourth International Conference "Equipment and structures diagnostics using the method of metal magnetic memory" was held in Moscow in February, 1999, in February, 2001, in February, 2003 and in February, 2007. The conference proceedings were considered at meetings of the International Institute of Welding (Lisbon, July 22, 1999, Ljubljana, July 11, 2001, Osaka, July 11, 2004). The totals of the conference are reflected in the IIW documents No.XI-714/99, No.V-1196-01 and No.V-1252-03.

During the period from 1994 till 2008 42 IIW documents with positive resolutions on the metal magnetic memory method were issued.

The International Standard ISO 24497-1:2007(E), 24497-2:2007(E), 24497-3:2007(E) on the metal magnetic memory method is approved in 2007 as a result of positive voting among 18 IIW member countries and more than 10 ISO Committee countries.

The metal magnetic memory method and appropriate testing instruments are used at more than 1000 Russian enterprises. Besides Russia, the method was implemented at a number of enterprises of 25 countries: Argentina, Angola, Australia, Bulgaria, Byelorussia, Canada, China, Finland, Germany, India, Iraq, Iran, Israel, Kazakhstan, Latvia, Lithuania, Macedonia, Moldova, Mongolia, Montenegro, Poland, Serbia, South Korea, Ukraine, USA.