The article considers state and prospects of contemporary methods and means for piston compressors health monitoring and diagnostics at hazardous continuous production facilities. There is a review of health monitoring principles, implemented in all the known monitoring systems. The equipment health criteria are described as well. The authors have carried out the diagnostic features selection for monitoring purposes and described the vibroacoustic signal sources. Methodology and algorithms of piston compressors diagnostics are also included in the article.
Kostyukov V.N., Naumenko A.P. Contemporary methods and means of piston compressors condition monitoring and diagnostics. Part 1 // Chief Power Engineer. - 2010. - № 11. - pp. 40-50
Monitoring purposes for technical objects are: a timely detection of incipient malfunctions, an observation of their development up to a critical state and a timely personnel warning on malfunctions occurrence in order to develop measures aimed at ensuring a maximal duration of the unit operation and a timely fault-free decommissioning for repair.
The monitoring time interval, starting with preparation for measurements and up to fulfillment of regulations, should be significantly shorter than the malfunctions development interval from the moment of detection to a critical level. Results of the units large-scale monitoring at petrochemical complexes show that the minimal intervals of malfunctions development up to critical levels do not exceed 10-20 minutes, but they can be significantly shorter – up to 3-5 minutes – due to the “human factor” adverse effect. The necessity to prevent accidents caused by such factors has determined emergence of automatic stationary systems for health monitoring of hazardous production facilities units, primarily in petrochemistry, metallurgy and railway transportation.
Thus, the radical difference between monitoring and diagnostics lies in necessity of taking into account the time factor. This gives us the following definition of the unit health monitoring (unit monitoring) - monitoring of the unit technical state (design of machine, unit, mechanism) for determination and prediction of entering the limiting state. Monitoring is diagnostics, expanded in time. The fundamental difference between health monitoring and parameters monitoring is the presence of the measured parameters interpreter in terms of the unit technical state (expert system for decision-making support on the unit health and further control).
Kostyukov V.N. Systems for real-time comprehensive health monitoring of equipment // NEFTEGAZ. - 2010. - pp. 44-45
A structural mathematical description of a vibroacoustic signal, obtained from a piston machine specific units with regard to a channel of vibroacoustic oscillations formation and distribution, is a diagnostic model. This model allows to select informative diagnostic features of malfunctions and defects.
The generalized structural model of the vibroacoustic signal, generated by different sources in the piston machine, is built in the presence and interaction of three main sources of vibro-acoustic oscillations in the unit, which are is identified by oscillations types: free damped, forced undamped, random broadband and narrowband oscillations.
In order to form the diagnosis-making algorithms, based on the vibroacoustic signal parameters and invariant to machines and mechanisms design, it is necessary to develop particular structural models of the vibroacoustic signal for a specific malfunction or defect on the basis of the generalized model.
Naumenko A.P. On some models of vibroacoustic signals structure in piston machines // Engine-2010. - 2010. - pp. 75-78
Fundamental causes of high costs and production losses are: poor observability, difficult controllability and, consequently, low stability of flow processes. The main factors conditioning such a situation are: difficulties in detecting hidden errors of the equipment design, production and mounting, as well as hidden nature of malfunctions occurrence and development, poor observability of the equipment degradation processes, human factor negative influence and, of course, absolutely ineffective system of schedule-based preventive repair, which is unable to root out emergency and unscheduled repairs, and therefore production downtimes and loss of resources.
Observability of the equipment degradation process allows to exclude emergency repairs and carry out all the units repairs according to their actual health in a scheduled manner, thus providing 100% elimination of emergency situations. When speaking about money saving, one should realize that there is not only reduction of material resources consumption, but that of the enterprise labor and financial costs, intended to eliminate the consequences of accidents, breakdowns and shutdowns losses.
The real increase of processing units run-to-repair up to 2-5 years (which is currently required by all of the companies from their plants) is impossible without implementation of health monitoring systems COMPACS® - the basic element of safe money saving production operation.
Kostyukov A.V. COMPACS system - a comprehensive solution for run-to-repair increase of production facilities operation // Modern systems for diagnostics and control of oil-refining and petrochemical equipment (Seminar of Chief Mechanics). - 2010. - p. 70-73
The article considers analysis of existing methods and means for piston compressors monitoring and diagnostics. The peculiarities of the diagnostic and monitoring systems implementation have been presented, the piston compressors main units, which monitoring and diagnostics is of the main focus, have been listed. Architectures and operational principles of the known systems for the piston compressors monitoring and diagnostics have been considered.
Foreign stationary systems for on-line monitoring of the piston compressors parameters exercise control over these parameters, not determining the reasons for their changes, caused by specific malfunctions and their hazard rates.
Real-time systems for the equipment technical state monitoring, proposed and developed in Russia for more than 30 years, are deprived of these drawbacks. The fundamental difference between the real-time monitoring systems and the considered on-line monitoring systems lies in the integrated automated expert system for diagnosis-making, which automatically and in real-time points to the staff the degree of malfunctions development and their danger for the piston compressors and a technological unit, through a "thin" automatic analysis of signals.
Kostyukov V.N., Naumenko A.P. Analysis of modern methods and means for piston compressors monitoring and diagnostics. Part 1. On-line monitoring systems // NDT world. - 2010. - №1. - pp. 64-70
The article considers the method of errors standardless assessment in machines assembling, based on analysis of the vibro-acoustic signals, related to unobservable errors in machines and units, arising within production and operation, some of which do not have an adequate representation in relations and intervals scales.
There has been established a canonical equation of connection between the signal diagnostic features and the machine state structural parameters, represented as ordinal scales; where the equation constitutes the first corner bisectrix of an information plane.
Modeling and experimental research results have been presented.
There has been received an assessment of a diagnostic error, caused by a stochastic communication between diagnostic features and structural parameters, which is inversely proportional to Spearmen's rank-order correlation ratio between them.
The vibro-acoustic method allows to single out during running and acceptance tests the machines with large values of errors and send them back for finishing, preventing their operation.
The proposed approach eliminates the need for training the diagnostic systems on machines-standards with known errors and significantly reduces financial and time costs for the diagnostic systems implementation.
Kostyukov V.N., Kostyukov Al.V. Errors assessment in machines assembling by a vibro-acoustic method // Assembling in mechanical engineering, instrument making. - 2010. - №1. - pp. 22-28
The technological cycle of the large volume current repair (TR-3), carried out in a depot, includes long and labor-consuming operations of removal, dismantling for audit, repair, assemblage, tests, transportation of the equipment and assemblies and their back mounting on an electric multiple unit. At the last stages of this cycle the repaired, tested and operable equipment can be damaged, as well as its working capacity, being a part of the electric multiple unit system, can be disturbed owing to violation of functional interrelations.
Lack of appropriate means and methods for an objective quality control of repair, assemblage and adjustment of responsible and most difficult systems of the electric multiple unit, i.e. first of all electrical circuits, within a limited idle time at the depot does not allow to carry out a high-quality control of the performed works. As a result, “raw” electric multiple units are admitted to an after repair running and besides undebugged (hidden) defects, which percentage reaches from 30 to 40 %, have many new ones, appeared due to a so-called human factor. Duration of a debugging stage, success of acceptance tests and further non-failure operation of an electric multiple unit in this case directly depends on debuggers’ qualification and their other subjective qualities.
It is possible to change radically the current situation on the basis of automatic systems for comprehensive diagnostics - to transfer the debugging stage from under a contact wire to a repair shop with simultaneous reduction of its duration, as well as to provide the quality assessment objectivity for the repair, assemblage and adjustment of the electric multiple unit equipment and systems and, as a result, to increase percentage of zero defects since the first presentation within acceptance tests. Such systems are based on the automated expert system for malfunctions detection, which excludes a diagnostician’s subjective errors and provides a reliable quantitative and qualitative assessment for a technical state of the electric multiple unit most difficult and responsible systems according to the main regulating documents requirements.
Kostyukov V.N., Kostyukov Al.V., Kazarin D.V. Equipment diagnostics in electrical circuits of electric multiple units when debugging and acceptance tests // Control. Diagnostics. - 2010. - №1. - pp. 26-35
A mathematical description for structure of a vibro-acoustic signal, obtained from a piston compressor specific assemblies with regard to the channel of vibro-acoustic oscillations formation and propagation, is a diagnostic model. This model allows to select the informative diagnostic features of the assembly malfunctions and defects.
One of the piston compressor most "problematic" assemblies is its valve. Number of valves per one cylinder usually ranges from four to eight and more. The report considers the model of vibro-acoustic oscillations, which have been converted into an electrical signal by dint of a sensor, mounted directly on the piston compressor valve or next to the valves group.
When considering the model, it was found that with an appropriate choice of locations for the vibro-acoustic signals sensors (on the piston compressor appropriate assemblies) one can diagnose the malfunctions occurrence in a double-acting piston compressor assemblies according to correlation of the second and more high-and low-frequency harmonics levels in an envelope spectrum of vibro-acoustic signals. Taking into account a modulation degree high sensitivity to changes in a modulating signal parameters, compared with a direct spectrum signal, it is advisable to use the frequency range that corresponds to a carrier frequency in vibro-acoustic oscillations, generated by gas flow.
Thus, the presented model of the vibro-acoustic signal allows to determine the most informative vibro-acoustic components, which can be used as the diagnostic features parameters for malfunctions in valves and other piston compressor components and parts.
Naumenko A.P. Patterns for vibro-acoustic signals of piston machines // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - pp. 114-120
Within limited financial resources, companies try to find ways to streamline all activities in order to achieve the best possible results at the lowest cost. Operation and repair of equipment in industrial enterprises play a leading role in solving this problem. Improving of the main and auxiliary personnel labor productivity, security and operational efficiency is of crucial importance, because there are no reserves, due to higher prices for products and expanding markets.
Operational efficiency of continuous production mostly depends on the amount of material and labor efforts for the equipment repair and on the amount of losses due to accidents and downtimes.
Growth of situational costs is induced by higher rate of material and labor resources waste due to lack of timely and targeted response to increase of the equipment wear rate caused by low observability of influencing factors in the conditions of a priori uncertainty.
The essence of technical management of hazardous continuous productions consists of early detection and purposeful influence on rate decreasing effect for material and labor resources waste during the equipment operation, which is provided by the monitoring systems implementation and effectiveness of the personnel actions in real time.
Kostyukov V.N., Kostyukov An.V., Makhutov N.A. Improving safety and operational efficiency of hazardous continuous productions // Monitoring and industrial risk management. Problems of diagnostics and non-destructive testing. - 2009. - pp. 53-65
Synthesis of diagnostic features, appropriate to the piston machines technical condition types, main failures and operation modes, arising both separately and simultaneously, and invariant to the machine construction - is an important issue. One step for this problem solution is to create the diagnostic signal model for the unit under test.
The most common model of the known is a batch action generalized model of a quasi-periodic vibroacoustic signal, proposed by V.N. Kostyukov.
This model shows that the frequency content of the low-frequency vibration spectrum and the vibroacoustic signal envelope, obtained by filtering in the high-frequency field and subsequent detection, are approximately equal. These spectra can be represented by an expansion in the characteristic frequencies, which can be divided into three groups. To evaluate the unit technical condition it is necessary to select and measure the components energy characteristics for each group.
This model describes large classes of the units under test failures. The model further development is the model, which describes the vibroacoustic signals with respect to their sources interaction, thus increasing the diagnosing accuracy and depth, but its use for developing the diagnostic algorithms is not obvious.
Therefore, it is advisable to consider a few examples of the vibroacoustic signal models when specific defects and failures occur, thus forming the piston compressors diagnostic features.
Naumenko A.P. Vibroacoustic model of the piston compressor diagnostic signal // Dynamics of systems, mechanisms and machines. - 2009. - pp. 39-44