Evaluation of Methods to Predict Safe Welding Conditions and Maximum HAZ Hardness in Steel Welding

1995 ◽  
Vol 117 (1) ◽  
pp. 46-56 ◽  
Author(s):  
J. P. Tronskar
Keyword(s):  
Oil And Gas ◽  
High Strength Steels ◽  
Offshore Structures ◽  
Structural Steels ◽  
Gas Production ◽  
Carbon Equivalent ◽  
Chemical Compositions ◽  
International Institute ◽  
Empirical Formulas ◽  
Offshore Industry

During the last ten years new structural steels of improved weldability have been introduced. In particular, structural steels for the fabrication of offshore structures have been greatly improved in this respect throughout this period. These steels have lean chemical compositions which are generally outside the range for which the existing HAZ hardness criteria and the International Institute of Welding carbon equivalent (CEIIW) formula were originally developed. This paper presents the results from investigations of the weldability of three normalised (Re min 350 MPa) and three quenched and tempered (Re min 500 MPa) offshore structural steels. Weldability testing was conducted to study the relative performance of the different steels and to obtain a comparison between the capability of the different methods to predict safe welding conditions to avoid cold cracking in steel welding. It has become a widespread practice in welding high-strength steels to incorporate maximum HAZ hardness restrictions in fabrication specifications, particularly so in the offshore industry. Maximum HAZ hardness restrictions are often a point of contention between fabricators and their clients due to the difficulties often experienced in meeting these hardness requirements. Problems meeting maximum HAZ hardness requirements have been encountered for applications where maximum hardness HRC 22 or Vickers HV10 260 have been imposed for materials exposed to sour service in oil and gas production, processing and transportation. Many attempts have been made to develop empirical formulas for the estimation of maximum HAZ hardnesses. This paper presents some of the more successful approaches proposed to date and compares their performance.

High Quality TMCP Production and Metallurgy of Niobium Bearing Steels

2016 ◽  
Vol 879 ◽  
pp. 820-825
Author(s):  
Steven G. Jansto
Keyword(s):  
Mechanical Properties ◽  
Continuous Casting ◽  
High Strength Steels ◽  
Value Added ◽  
Bearing Steel ◽  
Carbon Equivalent ◽  
Chemical Compositions ◽  
Market Demand ◽  
Production Scale ◽  
Lower Carbon

The technological and metallurgical advancements of value-added niobium (Nb) microalloyed thermo-mechanical controlled process (TMCP) plate steels continue to be developed for more demanding end user requirements. The market demand for reduced fuel consumption and CO2 emissions in the automotive and construction sectors have further increased the demand for these new and advanced higher quality Nb-bearing steel grades. Often, the transition from laboratory melted and TMCP hot rolled heats to the production scale requires some continuous casting, thermal and mechanical metallurgy adjustments from the laboratory results in order to accomplish proper industrial continuous casting and hot rolling processes. These advanced high strength steels are microalloyed with Nb, Mo and/or other elements which affect the austenite-ferrite transformation. Niobium enables achievement of substantial grain refinement when the plate is rolled with the proper reduction and thermal schedule. The effects of these microalloying elements on the continuous cooling transformation behavior must be carefully controlled during the reheating and rolling process to successfully achieve the desired mechanical properties. TMCP applications have been successfully developed in numerous product sectors with thickness exceeding 120 mm. Since the very fine grained microstructure improves toughness and increases the yield strength, this TMCP process enables the required tensile properties with the growing trend to leaner chemical composition designs (less than 0.10%C) and excellent toughness properties. The consequence of leaner chemical compositions, especially lower carbon content and lower carbon equivalent enhances mechanical properties, fabrication and weldability.

Rosenhain Centenary Conference - 2. Design implications for materials selection 2.8 Weldability and toughness specifications for structural steels in Japan — with special reference to WES-155 and -156

1976 ◽  
Vol 282 (1307) ◽  
pp. 247-258 ◽  
Keyword(s):  
Large Scale ◽  
High Strength Steels ◽  
High Strength ◽  
Structural Steels ◽  
Steel Plates ◽  
Carbon Equivalent ◽  
Small Scale ◽  
Materials Selection ◽  
Cooperative Research ◽  
Standard Steel

During the last decade, the specifications, WES-135 and -136 played important guiding roles for developing and standardizing weldable high strength steels and structural steels for low temperature applications. In WES-135 which was established in September 1970, equivalent carbon content, C eq is adopted as an indication of the weld cracking susceptibility for high strength steels In order to accurately estimate the cracking susceptibility, a new parameter, P cm , is adopted as an indication of the carbon equivalent since March 1971. On the other hand, the toughness requirements specified in WES-136 are based on the correlation between small-scale tests and large-scale brittle crack propagation arrest tests as expressed in terms of K c -value. In this standard, steel plates are classi e into two classes of G and A, where G is generally accepted for welded structures where hazard of brittle fracture is anticipated and A is used for arresting a propagating crack. In order to establish revised toughness requirements for G class steels, comprehensive cooperative research works have been conducted since 1971. In this paper, the descriptions are focused on the weldability and toughness requirements of WES-135 and -136, their connexions with other standards, and the points under continuous examination.

scholarly journals Analysis of Operational and Seakeeping aspects in the Design of PSV type for the Colombian Caribbean Sea

2016 ◽  
Vol 10 (19) ◽  
pp. 47
Author(s):  
Jairo H. Cabrera ◽  
Cinthya Marcela Medina
Keyword(s):  
Oil And Gas ◽  
Offshore Structures ◽  
Operational Conditions ◽  
Extraction And Separation ◽  
Specific Support ◽  
Maritime Operations ◽  
Specific Activities ◽  
Offshore Industry ◽  
General Cargo

Colombia is currently searching for oil and gas at sea as new exploratory frontiers so as to incorporate new reserves. With the beginning of maritime operations comes the need for large offshore structures that allow the extraction and separation of oil and gas before transporting it to land. Most of these platforms require specific support and supply vessels, carrying a variety of loads, from liquid and bulk up general cargo, and various specific activities such as towing, rescue staff in case of accidents, firefighting and positioning anchor handling. In the offshore industry, these are known as PSV (Platform Supply Vessels). e main purpose of this work is the hydrodynamic PSV considering the environmental and operational conditions of the Colombian Caribbean including a case study.

Contribution to the Evaluation of VIV Analyses Using Wake Oscillator and Vortex Tracking Models

2008 ◽  
Author(s):  
Daniel Lyrio Carneiro ◽  
Gilberto Bruno Ellwanger ◽  
Nelson Szilard Galgoul
Keyword(s):  
Degrees Of Freedom ◽  
Oil And Gas ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Low Frequency ◽  
Offshore Structures ◽  
Gas Production ◽  
Current Profile ◽  
Mooring Lines ◽  
Wake Oscillator

Fatigue due to vortex-induced vibrations (VIV) is one of the major uncertainties today in the design of slender offshore structures, such as risers, pipelines, umbilicals, tendons and mooring lines, required for oil and gas production in deep waters. The absence of reliable tools for quantitative analyses of this phenomenon is a technological barrier, which is being faced by several research groups. This paper presents valuable VIV results achieved by the author, using “wake oscillator” and “vortex tracking” models, when researching for his M. Sc. dissertation. Time domain analyses were performed using a commercial software. First results describe the response of the evaluated models for two degrees-of-freedom rigid cylinders by tracing lateral displacement versus flow velocity curves. These curves are plotted over others previously published in recognized recommended practices, articles and theses. Afterwards, VIV analyses results for a steel catenary 10-inch diameter riser in three-dimensional current profiles were compared to measured values. The considered riser, installed in 910m water depth offshore Brazil, is possibly the only monitored SCR with no VIV suppression devices in the world today. The results were considered satisfactory, despite some discrepancies: the model which appeared to be one of the most attractive for the rigid cylinder case, failed to predict VIV in the SCR under an irregular current profile, for example. Vortex tracking models presented excessive low frequency response in the SCR analyses. Authors believe that this response is unrealistic, and these frequencies can be dissipated by using a more adequate damping model than that employed by the utilized program.

Breaking Load on Jacket Structure

2016 ◽  
Author(s):  
Sruthi Chandrasekar ◽  
Sriram Venkatachalam
Keyword(s):  
Wave Breaking ◽  
Oil And Gas ◽  
Impact Load ◽  
Breaking Load ◽  
Gas Production ◽  
Oil And Gas Production ◽  
Depth Analysis ◽  
Duhamel Integral ◽  
Offshore Industry ◽  
The Impact

Jackets are structures used in the offshore industry as a bottom supported platform for oil and gas production. The jackets have to be built in order to withstand the harsh sea environment. Such designs demand in depth analysis to predict the loads acting on the structure and its response. Depending on the sea states in which the structure needs to be installed, breaking load can be important. Estimation of breaking load for single cylinder exists in literature, since the breaking load on the jacket structure needs a lot more clarity. The aim of this paper is to estimate the impact force on a model jacket using Duhamel integral, which was not explored before. The impact load so far analyzed was compared with theoretical explanations given by Goda, et al. (1966), Wienke and Oumeraci (2005). The scope of the study is limited to plunging type of breakers. Five loading cases include wave breaking at far-front of a structure, in front of structure, on the front leg, on the rear leg and a non-breaking case was considered.

scholarly journals Resonant Motions of Dynamic Offshore Structures in Large Waves

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 352
Author(s):  
Ove Tobias Gudmestad
Keyword(s):  
Drag Force ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Gas Production ◽  
Mass Force ◽  
Oil And Gas Production ◽  
Damped System ◽  
Loading Function ◽  
Non Linear ◽  
Marine Engineering

In marine engineering, the dynamics of fixed offshore structures (for oil and gas production or for wind turbines) are normally found by modelling of the motion by a classical mass-spring damped system. On slender offshore structures, the loading due to waves is normally calculated by applying a force which consists of two parts: a linear “inertia/mass force” and a non-linear “drag force” that is proportional to the square of the velocity of the particles in the wave, multiplied by the direction of the wave particle motion. This is the so-called Morison load model. The loading function can be expanded in a Fourier series, and the drag force contribution exhibits higher order harmonic loading terms, potentially in resonance with the natural frequencies of the system. Currents are implemented as constant velocity terms in the loading function. The paper highlights the motion of structures due to non-linear resonant motion in an offshore environment with high wave intensity. It is shown that “burst”/“ringing” type motions could be triggered by the drag force during resonance situations.

The Conquest of the Inner Space: Design and Analysis of Offshore Structures

2008 ◽  
Author(s):  
Gu¨nther F. Clauss
Keyword(s):  
Oil And Gas ◽  
Production Systems ◽  
Outer Space ◽  
Offshore Structures ◽  
Ocean Engineering ◽  
Public Attention ◽  
Space Design ◽  
Design Characteristics ◽  
Offshore Industry ◽  
Water Depths

Spectacular missions to the moon, the Mars and to other planets of our solar system has boosted public attention to the outer space for the last five decades. During the same period mankind has also conquered the inner space — with fantastic innovations and fabulous inventions — however, hidden under the sea surface, and hence widely unnoticed. While searching for new promising oil and gas fields the offshore industry operates in water depths that have never been explored before. Production systems already reach down to 2000 m, and will probably conquer greater water depths during the next years. Extreme environmental conditions in addition to these enormous water depths call for special solutions. This paper deals with recent developments of offshore deepwater production technology, e.g. SPARs, TLPs, Compliant Towers and huge mono-buoys. After a short survey of the development in ocean engineering from the first shallow water platforms in the Gulf of Mexico in 1947 to today’s deepwater production systems off the Brasilian coast the paper summarizes the principles of platform dynamics in waves to illustrate the advantages of specific design characteristics.

Green Water Phenomena on a Twin-Hull FLNG Concept

2014 ◽  
Author(s):  
Riaan van ‘t Veer ◽  
Ebert Vlasveld
Keyword(s):  
Potential Flow ◽  
Oil And Gas ◽  
Gas Production ◽  
Point Of View ◽  
Green Water ◽  
Linear Potential ◽  
Oil And Gas Production ◽  
Large Wave ◽  
Water Problem ◽  
Offshore Industry

This paper investigates — based on model tests and potential flow calculations — several phenomena associated with the green water problem in severe sea states. The topics investigated are: the wave characteristics of the severe and steep sea states, the behavior of the vessel in these waves, the relative motions at the bow and the height of water on deck. The green water problem is of interest since many floaters used for the oil and gas production by the offshore industry are permanently moored for typically 20 years or more, and they will experience severe storm conditions with large wave heights. The investigations concern an unusual vessel type: SBM’s innovative midscale Twin-Hull FLNG concept [1]. The floater concept is to join two (standard) LNG carriers together to obtain sufficient storage volume and process deck space. The concept is under development and one aspect, from operability point of view, is the probability for green water. For this purpose a first model test campaign has been carried out. The Twin-Hull FLNG concept has been tested in extreme sea states which are typical for offshore Brazil and East-Africa. Linear potential flow calculations were applied to predict the freeboard exceedance based on relative motion amplitude operators. The correlation to the measured data is discussed. Although the research is dedicated to the Twin-Hull FLNG vessel, the observed phenomena are considered applicable to any stationary vessel in general.

Integrity Management of Deep Water Floating Production Facilities: Towards Better and Safer Workforce Personnel

2005 ◽  
Author(s):  
Alberto C. Morandi ◽  
John K. Galiotos
Keyword(s):  
Gulf Of Mexico ◽  
Deep Water ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Gas Production ◽  
Petroleum Engineering ◽  
Process Equipment ◽  
Integrity Management ◽  
Offshore Industry ◽  
Production Facilities

The oil and gas industry has, over the recent years, invested heavily in multi-billion dollar projects aimed at developing an exploration and production infrastructure in the deepwater Gulf of Mexico. The integrity management of such facilities will be critical for the industry in the coming years. Competency of Personnel stands out as the most important of these areas. Although office-based personnel plays an important part, the personnel working offshore such as OIMs, supervisors, ballast operators and topsides operators will make critical decisions that may affect the safety of an entire production unit. Alliances between offshore industries, contractors and community colleges generate curricula exclusively tailored to provide specific training and retraining to new hires on the duties and tasks performed by the oil and gas production technician and encumbered workers of the offshore industry. Offshore oil and gas extraction organizations are faced with unique challenges, when needing competent, skillful, safe, and well trained workers. Liabilities from non-trained personnel, and the understanding that safety is priority #1 on the platform, are paramount in concepts of the offshore workforce. Unlike other areas of the world, production in the Gulf of Mexico has been predominantly on the shallow water continental shelf and many organizations are faced with the challenges of developing new sets of skills for different types of production facilities used in deep water. Training of technicians, who will be operating an offshore deepwater platform, should cover topics that include ballast control and stability management, vessel station-keeping, riser management, response to hurricanes and loop currents, hydrocarbon and operations safety, process equipment and systems, troubleshooting, sub-surface geology, petroleum engineering and drilling technology. This paper discusses collaborative initiatives and discusses specific solutions. Based on a multi-year experience generating of such curricula, recommendations are provided to industries that want to establish such training programs for their technical personnel.

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