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This paper specifies the physical - mechanical properties that shall be guaranteed for the tubes and the other components (return bends & plug headers, elbows, junction boxes, tube supports, anchors, tube guides or tube sheets), named synthetically PRFT, of the coils of petrochemical plants and oil refineries furnaces - FC. It also presents the main processes that determine the modification / alteration of these properties during the use of FC, it analyses the modalities in which these properties intervene in the FC design calculations and it highlights the influences of these properties upon the reliability, maintainability, availability, durability and safety in exploitation of FC. The original contributions of our work, concerning the FC made of PRFT manufactured from various classes of materials, are the followings: a) definition of some pertinent analytical expressions for the dependences of operating temperature on the minimum guaranteed physical - mechanical properties of PRFT materials; b) formulation of a strategy for the increase of the FC reliability and durability, based on the assessment of the effective physical - mechanical properties of PRFT materials. Lucrarea precizeaza caracteristicile fizico - mecanice care trebuie garantate pentru tuburile - FT şi celelalte componente (returbenţi sau cutii de întoarcere, coturi din ţeavă, elemente fasonate de îmbinare şi/sau de racordare, plăci tubulare, suporturi, suspensii) - FP ale serpentinelor cuptoarelor din rafinariile de petrol şi instalaţiile petrochimice - FC, prezint š principalele procese care determinš modificarea / degradarea acestor caracteristici în cursul utilizšrii FC, analizeazš modalitššile în care aceste caracteristici intervin în calculele de proiectare ale FC şi evidenšiazš influenšele acestor caracteristici asupra fiabilitššii, mentenabilitššii, disponibilitššii, durabilitššii şi siguranšei în exploatare a FC. Contribušiile originale ale lucršrii, referitoare la FC cu FT şi FP realizate din diverse clase de materiale, sunt: a) stabilirea unor expresii analitice pertinente pentru dependenšele de temperatura de lucru ale caracteristicilor fizico - mecanice minime garantate ale materialelor FT şi FP; b) formularea unei strategii de creştere a fiabilităţii şi durabilităţii FC. [ABSTRACT FROM AUTHOR]

This work presents the technology that is conceived and applied by the authors for the repair of a natural gas transmission pipeline, damaged by an unlawful interference, which consisted of the stripping of a part of the pipeline, removing a segment from the anti-corrosion protection layer in the stripped area and producing a local defect by perforating the steel tube of the pipeline. Based on the critical analysis of several possible technical solution to repair the pipeline, the decision was made to eliminate the defect by using the weld deposition; the particularities of developing the preliminary specifications of procedures for repair by welding, its qualification and applying the qualified procedure for the repair of the damaged pipeline, described and commented in the work, must be known and considered by those who must execute similar corrective maintenance works upon the pipelines in the natural gas transmission systems. [ABSTRACT FROM AUTHOR]

This paper presents the results of the investigation conducted by the authors in order to identify the causes of the unexpected operational failure of a pipeline belonging to the National Gas Transmission System. The researches, based on a complex experimental program, led to the conclusion that the failure occurred due to: a) an accidental mechanical loading of the pipeline, generated by a landslide occurring in the area in which it was laid; b) the high level of residual stresses and low toughness properties of the steel pipe in which failure occurred. Based on the research performed, the technical conditions for the pipeline safe operation after replacing the damaged pipe have also been defined. [ABSTRACT FROM AUTHOR]

The paper presents modern technical solutions for interconnecting new, rehabilitated or upgraded pipes to the pipelines of the natural gas transmission systems in operation. The use of these technical solutions ensures the fulfillment of one of the major objectives imposed by the effective legislation on activities performed in the natural gas sector "ensuring the continuity and security of natural gas supply to customers." Using the technical solutions presented within this paper on the selection of equipment and components used to accomplish the interconnection of pipes that make up the natural gas transmission systems and the rational design of technologies for the operations which are necessary for interconnecting pipelines (mainly assembly and welding) represent a secure way to optimize the interconnecting works performed on pipelines, minimizing the duration, the cost and mitigating the technical risk associated to the performance of such works. [ABSTRACT FROM AUTHOR]

This paper analyses and resolves the extremely complex problems of performing the technological operation of straightening of the steel plates and strips intended for the manufacture of static equipment, of the type pressure vessels and storage tanks, for petroleum refineries and petrochemical plants. The procedure and software product developed by the authors for the design of the technological operation of straightening of the steel plates and strips on straightening machines with multiple rollers highlights the parameters describing the regime for the straightening operation and the modalities for the adequate selection of their values, as well as the factors influencing the shape precision of the straightened semiproducts and the energy input needed to perform the straightening operation. The information from the present paper is extremely useful for the selection and rational exploitation of the straightening machines and, in this manner, for the appropriate quality assurance of the semi-products intended for the construction of static equipment, with special technical parameters (big overall dimensions and masses, high operating pressures, high or low operating temperatures, aggressive working fluids etc.), from the petroleum and gas processing plants. [ABSTRACT FROM AUTHOR]

This paper presents and analyses the existent procedures and proposes a new procedure for the design of the reinforcing sleeves made of composite materials which are applied in the areas with local surface defects (of the type metal loss) of the transmission pipelines intended for petroleum, liquid petroleum products and natural gas. In addition, the technical requirements regarding the definition and qualification of the pipelines repair systems using composite materials, and the information which must be made available as input data for the design of reinforcing sleeves intended for various applications (repair of pipeline with different locations, shapes and dimensions of the metal loss – like defects) are also presented. The items discussed and the solutions formulated in the paper can be useful both to the manufacturers of the components of the composite materials repair systems and to the ones dealing with the design and performance of the maintenance works for the pipelines belonging to the transmission systems of petroleum, liquid petroleum products and natural gas. [ABSTRACT FROM AUTHOR]

In this paper there is outlined the analysis performed by the authors regarding the temporal evolution of the steel pipes quality requirements for the natural gas transmission pipelines. It shows the history of the implementation of prescriptions regarding the chemical composition and the tensile mechanical characteristics, focusing mainly on the implementation of requirements regarding the toughness in the standards that refer to the pipe quality, but also on the qualitative evolution of these prescriptions, consisting in passing from the toughness checkings based on the impact energy (determined by the notched-bar impact test), to checkings based on the percet shear area ( having a fibrous appearance) on the impact fracture surface (determined by the drop-weight tear test – DWTT) and to the checkings based on the crack tip opening displacement (determined by fracture mechanics tests). [ABSTRACT FROM AUTHOR]

The paper shows, analyzes and comments the results obtained by applying an experimental programme that aimed for the determination of the strength and toughness properties of pipes and welded joints of some superannuated pipelines of the national natural gas transmission system. The specimens used for this experimental programme were processed from the samples drawed from two superannuated pipelines: one sample from the pipeline Ungheni – Găneşti, operated since 1928 and one sample from the pipeline Ceanu Mare – Cluj, operated since 1948. The experimental results are analyzed and commented in terms of the current requirements regarding the strength and toughness of steel pipes for natural gas transmission pipelines. [ABSTRACT FROM AUTHOR]

This paper analyses the main degradation mechanisms of pipes used in furnaces from refineries and petrochemical plants and suggests a procedure for determining the cumulative damage of these pipes, given their long use in fluctuating pressure and temperature regimes according to the needs of the technological processes served by the furnaces. It is established that Fitness-For-Service assessments for furnace pipes in refineries and petrochemical plants must be made considering the effects of creep phenomenon, combined with those of cyclic loading (fatigue) and with the action of the fluid that flows through pipes (which can cause superficial carburization on the inside surface of the pipes) and with the working environment inside the furnace (which can cause oxidation and superficial decarburization of the pipes). The proposed methods for examining and checking the pipes during periodic inspections of the furnaces are also indicated together with the ways these results may be used to increase the confidence level of the information provided in the procedure proposed by the authors for continuous monitoring of the pipes in use. [ABSTRACT FROM AUTHOR]

This paper presents a procedure for determining the remaining strength factor (RSF) for pipelines that have components subject to local metal loss. The demands from API 579-1/ASME FFS-1 regarding the characterisation of the flaws' gravity by using the minimum value of RSF are respected by applying the procedure proposed by the authors. The case studies presented in the paper lead to the conclusion that, for an operative and sufficient level of confidence evaluation of pipelines with this type of flaws, the RSF value calculated by considering the profile and real dimension of the detected flaws can be utilized, and that the decision of applying the laborious method for determining the minimum value of RSF, recommened by API 579-1/ ASME FFS-1, is not always justified. [ABSTRACT FROM AUTHOR]

This paper shows the particularities of developing a risk analysis in order to determine the safety distances between the national gas transmission pipelines system and the social and industrial objectives located in their neighborhood. Based on the event tree analysis on pipeline commissioning, on the causes and probability of occurrence of such events we chose to analyze the worst case scenario from the perspective of human health and safety, of the security of constructions, equipment and environment in the vicinity of the pipeline and, taking this worst case scenario into account, we drafted a procedure for the determination of the safety distances. The paper also shows the main physical and procedural means and methods to remedy and settle the risk entailed by the operation of the gas transmission pipelines for the purpose of providing some rationally sized safety areas. [ABSTRACT FROM AUTHOR]

In this paper there is defined the functional role of fracture arrestors designed in order to be installed over natural gas transmission pipelines and there is made an original classification of these, while presenting the constructive features and the way of achieving a wide range of arrestor types. There is presented an analytical method for assessing the reinforcement effects of the application of fracture arrestors with continuous disposal over pipelines, method that can be successfully used while designing (determining the thickness of) fracture arrestors of this type. [ABSTRACT FROM AUTHOR]

This work highlights, by analyzing the causes of some technical accidents, the danger represented by the presence of lamination-like flaws in the steel pipes natural gas transmission pipelines are made of and presents a method of numerical simulation of the process that causes the extension of these flaws and that can lead to the explosive failure of these pipelines, many times accompanied by burning. The work also accentuates the fact that the severity of lamination -- like flaws of the pipes the natural gas transmission pipelines are made of is directly correlated to the mechanical strength and toughness properties of the steel the pipes are made of and to the particularities of the operating conditions of pipelines, mainly to the frequency and the amplitude of the pressure variations of the conveyed gas. [ABSTRACT FROM AUTHOR]

In this work there are analyzed the main toughness criteria that have to be fulfilled by steel pipes designed for natural gas transmission pipelines and there are also suggested some modalities for combining mechanical strength and toughness criteria while designing these types of pipelines. The application of the solutions suggested within this paper ensures the avoidance of brittle failure of in-service pipelines, conferring them the ability to arrest the propagation of ductile fracture and causes the significant diminution of the risk associated to the use of natural gas transmission pipeline systems. [ABSTRACT FROM AUTHOR]

In this paper there is presented the proposal of the authors regarding the use of the hot brine hardenability test, usually intended to characterize the hardenability of low-hydrogen steels, for determining the maximum values of the hardness in the heat affected zone of welded joints of steel components, performed while constructing pipes for oil and gas pipelines. Knowing the maximum values of the hardness of the microstructures that can be generated within the heat affected zone of welded joints, there can be made a relevant choice of the hydrogen scale of covered electrodes used during weld repairs and there can be conceived cheap and reliable in-service repair technologies for natural gas transmission pipelines made of steel. [ABSTRACT FROM AUTHOR]

In this paper we present an assessment procedure consistent with the level 3 methods recommended by API 579 / ASME FFS-1, of a local metal loss defect detected on the outer surface of the steam boiler drum mantle of a thermoelectric power plant. We analyze several solutions for corrective maintenance work to restore and re-commission the drum mantle. In selecting the optimal solution conforming to the requirements of the ISCIR PT C1-2003 and C4/2-2003 Technical Prescriptions we employed criteria addressing mainly the welding suitability and the behavior of the materials involved, during and after welding. [ABSTRACT FROM AUTHOR]

In this work the repair technologies of the fuel fluid transmission pipelines (oil, liquid petroleum products and natural gas), with and without welding operations, are analyzed comparatively. There has been highlighted the advantages and disadvantages of the repair technologies based on the welding application of additional elements (patches or full encirclement steel sleeves) and those based on composite reinforcement sleeves. It has been also presented the criteria used for selecting the repair technologies (with and without welding) when the in-service repair is carried out. [ABSTRACT FROM AUTHOR]

This paper outlines the experimental research conducted by the authors to highlight the efficiency of postwelding application of the ultrasonic impact treatment (UIT) on fillet welded lap joints in case of metal constructions subject to variable operating stress. The series of experiments consisting in fatigue testing specimens extracted from test-plates presenting fillet welded lap joints, subject and respectively not subject to post-welding UIT, led to the conclusion that increased fatigue behavior performances under UIT is relatively low by reference to the increased construction costs generated by the application of such a treatment. [ABSTRACT FROM AUTHOR]