Nr. 1/2016

 
 

Revista Sudura 1/2016

The articles are published in Romanian and English languages

 

❯ Risk engineering of load-carrying structures Part II – Probabilistic mechanical reliability methods*

Prof. Dumitru Dragoș Cioclov Profesor onorific al Universității Politehnica din Timișoara e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract: The essay deals with the perennial problem of the safety of load-carrying structures in circumstances en- countered in service. The exposure goes beyond the view promoted in classical engineering which has at the root deterministic “safety factors” which set a margin at the attainment of the limit state which marks the failure or unacceptable degradation. It is introduced the new probabilistic paradigm which is able to take into account and manage unavoidable uncertainty and variability encountered in the operation of load-carrying structures. The general methodology of probabilistic analysis of the failure risk kmown as “Load-Strength Interference Method” is introduced in a mathematical formalism based on the convolution multiple integrals which has the capacity to take into account, via specific random variables, the probability features of the physical mechanisms of structural failure. Numerical Monte Carlo simulation method is introduced and used in a sensitivity study of the failure risk probability of a structural element which both static tensile strength and acting tensile loading, both, follow Normal distribution. The standard deviation of specific random variables, related to structural element strength and applied loading is the variable parameter in the study enabling to evince dangerous conjunctions, i.e. when the probability of failure has sufficiently high values to arise concern. Keywords: load-carrying structure, safety, failure, performance function, probability model, convolution integral, reliability, Monte Carlo simulation, covariance, reliability.

Technological solutions for preventing hydrogen induced cracking when repairing by welding hydrocarbons transmission pipelines – Part II

Prof. Gheorghe Zecheru1), Dr. Marius Florin Bârsan2), Prof. Andrei Dumitrescu1), Assoc. Prof. Gheorghe Drăghici1) 1)Universitatea Petrol – Gaze din Ploiești, 2) S.N.T.G.N. „TRANSGAZ” Mediaș e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract: When repairing the defective areas of the transmission pipelines intended for petroleum, liquid petroleum products and natural gas, using procedures which include fusion welding operations executed onto out of service or in-service pipelines, two unwanted phenomena could take place: burn through of the pipe wall due to the action of the electric arc used as an energy source for welding and hydrogen induced cracking (also named cold cracking or delayed cracking) of welded joints. This paper presents the results of a theoretical and experimental research program aiming at tracing and ranking according to their importance the factors that determine the occurrence of the second phenomenon and at assessing the technical and technological solu- tions which avoid its triggering and ensure the good quality of the welded joints when repairing transmission pipelines by welding. Keywords: Hydrocarbons transmission pipeline – HTP; HTP repair by welding; Repair of in-service (under pressure) pipelines; Hydrogen induced cracking /old cracking/delayed cracking of welding joints – HIC

Results of the research work performed by the specialists from the Petroleum-Gas University of Ploiesti in the field of welding

Prof. Mihail Minescu Universitatea Petrol-Gaze din Ploiești e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract: In the petroleum and petrochemical industry, equipment of the most diverse and complex kind is used in very tough working conditions and it has to provide an increased operational safety. Therefore, for its manufacturing, materials and technologies of the most modern type are used and they require a special approach. Along the 65 years of existence, under various names, of the Electrical and Mechanical Engineering (IME) Faculty from the Petroleum-Gas University (UPG) of Ploiesti, its didactical and research staff had constant preoccupations in the field of the design and manufacture of the petroleum, petrochemical and refinery equipment, as well as of the equipment for hydrocarbon transmission and storage. In the framework of these researches, the problems connected to the use of welding technologies and of welding-related processes had and have a special place. The issues regarding welding have been approached with competence by the Professors Dumitru Rașeev, Viorel Micloși, Nicolae Napoleon Antonescu and VLAD ULMANU. Honouring the memory of Professor Vlad Ulmanu, the main coordinator in the last 25 years of the research team that have dealt with subjects concerning welding, this paper will present the main achievements of this team. The research work has been oriented towards the adaptation of some welding processes for the manufacture of the petroleum equipment for drilling and extraction, for the manufacture and repair of the petrochemical and refinery equipment, as well as for the manufacture and repair of the petroleum and gas transmission pipelines. The results of the research work performed in the IME Faculty have been materialized in an important number of products and technologies, patents, Ph.D. theses, specialty papers which have been published in renowned journals from our country and abroad, papers presented at national and international scientific conferences, but the most important achievements are the ones that have solved difficult technical problems required by the commercial societies from the field of petroleum and gas and not only, societies that have appealed and appeal with confidence to the specialists from our university.

Flash butt welding of dissimilar materials for rolling stocks

Ing. Iulian Vîrgolici, Voestalpine VAE Apcarom Buzău SA e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract: The paper describes the flash butt welding technique of two dissimilar materials: austenitic manganese steel and railway steel used in rolling stocks, heart block wings and tails. This technique was demanded by the need of using superior physical and mechanical properties materials in the construction of railway devices. This should be materials that have a high wear resistance, which would increase the operational duration and safety, and decrease the wear out and maintenance costs of the railway device, and lastly but not least these materials would help increase the speed of the rolling stock. The joining of the injected heart block with the two wings and tails is done by using flash welding process. The welding and testing procedures are presented.

THE SOCIETY INFORMS YOU CONTENTS

  • Calendar of scientific events 2016
  • Personals
  • ASR events from April 2016, Pitesti
  • ASR Courses 2016
  • Course - Welding coordination personnel in accordance with SE EN 1090
  • List of companies with advertisements in SUDURA 1/2016