PSI - Issue 16

Borys Paton et al. / Procedia Structural Integrity 16 (2019) 176–183

177

Borys Paton et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Keywords: Acoustic emission; continuous monitoring; pipeline; high temperatures; prediction; power plant; breaking load.

1. Introduction

Pipelines exposed to high temperatures in operation, are high-risk industrial facilities. During operation, the metal of which they are made accumulates damage, caused, in particular, by violation of operating conditions, varying loads, corrosion and chemical processes and a number of other factors. As a rule, there is no direct dependence between pipeline operating period and degree of its damage, and it is also quite difficult to separate damage caused by the impact of each of the determinant factors. In this connection, comprehensive assessment of material damage, without detailing the factors, causing the damage, appears to be the most promising. Its main objective is accident prevention. Irrespective of the causes for accident occurrence, their consequences can be quite grave. Therefore, continuous monitoring of structure serviceability and its prediction for a period of time required to prevent the danger, becomes urgent to ensure safe operation of structures. This is largely due to the fact that calculations of load-bearing capacity of structures and structural elements, providing their sufficient operational reliability, are difficult for a number of reasons, the most important of which are:  insufficient study, incompleteness or unreliability of initial data for calculation performance  complexity, and more often impossibility of prompt acquisition of data in service on current state of structures, particularly, at their complex loading  danger, and sometime, impossibility of conducting experiments, in order to determine the load-bearing capacity  inaccessibility of facilities in some cases for conducting reliable nondestructive testing. As a result, any structure, even after passing current testing, has problem areas, substantiation of operating reliability of which is quite complicated, and sometimes even impossible, particularly after extended operating period. An effective tool for solving the problem of ensuring operating reliability of structures is creation of information measurement systems, allowing its assessment to be performed already at the testing stage under the conditions of forthcoming operation, as well as monitoring this structure serviceability directly in operation. Modern development of computer technology, radio electronics, applied mathematics, test equipment, materials strength and continuum mechanics science, allow solving the problem of continuous monitoring of structure performance in service at a quite high level. Functioning of information-measuring systems requires regular acquisition of on-line data, primarily about the state of structure components and various kinds of defects, which accumulate during operation. With availability of data about the structure and respective processing of this information, its load-bearing capacity can be promptly evaluated in real-time. This, in particular, provides large engineering and economic benefits in those engineering fields, where lack of knowledge about the actual service loads, true state of structure material, changing during its operation, may lead to essential errors, when assigning the working parameters. At present, automatic monitoring systems are rather widely applied which are based on checking the running of technological processes, associated with processing, producing or application of various products in energy cycles. At the same time, much less attention is given to monitoring the state of structures applied for implementation of these processes. As a rule, structure performance is assessed at scheduled stopping of the production process, when conducting number of technological operations on ensuring the technical possibility of inspection. Most often it is impossible to perform 100% inspection of the structure because of extremely large scope and cost of the work, involved in its performance. As a rule, just individual sections are selected for inspection, which do not always correspond to the most damaged areas of the structure. The problem of structure monitoring can be solved with success with application of the method of AE, which emerges in materials at critical combination of certain impact factors, leading to emergence or development of defects. A feature of this method is the ability to check material state at large distances from the site of transducer 2. Results of experimental studies and their discussion