Rosenhain Centenary Conference - 1. Engineering requirements 1.3 Materials requirements for offshore structures Keynote speech

Thanks to the careful organization of this conference, the unambiguous definition of its scope, prior circulation of papers, and the example to be followed as outlined by Kelly in his account of the work of Dr Rosenhain, it is possible at this stage to save precious discussion time by addressing the topic of engineering requirements for structural steels almost without preamble. The three papers in this session, on bridges by Harper, line pipe by Mercer, and offshore structures by Cotton, are completely complementary. Thus Harper, although obviously aware of the necessary inhibitions of the bridge designer, arising simply from the need to ensure safe erection, and long operating lives despite the rigours of wear and weather, and the maintenance of public confidence, shows such an open mind that he would consider the use of adhesive joints in future constructions. In so doing he implies the invitation to consider other far reaching ideas that could be introduced. Mercer’s paper is packed with information, in terms of numbers that stretch the imagination. Yet the sources are authoritative, and a fair impression is given of the challenge of pipeline construction to be expected through the next decade. Cotton gives a balanced comparison of the relative merits of concrete and steel offshore structures, not without confirmation that the former embody more steel than the latter. In addition, he mounts a vigorous challenge with regard to existing methods of quantifying notch toughness requirements, ranging from material selection, through fabrication procedures to quality control. He is quite specific in describing particular problems of other types of service failure, in need of the attention of the physical metallurgist

1995 ◽  
Vol 117 (1) ◽  
pp. 46-56 ◽  
Author(s):  
J. P. Tronskar

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.


Author(s):  
Junfang Lu ◽  
Bob Huntley ◽  
Luke Ludwig

For cross country pipeline welding in Canada, welding procedures shall be qualified in accordance with the requirements of CSA Z662 Oil and Gas Pipeline Systems. For pipeline facility and fabrication welding on systems designed in accordance with CSA Z662 or ASME B31.4, welding procedures qualified in accordance with the requirements of ASME Boiler & Pressure Vessel Code Section IX are permitted and generally preferred. Welding procedures qualified in accordance with ASME IX provide advantages for pipeline facility and fabrication applications as a result of the flexibility achieved through the larger essential variable ranges. The resulting welding procedures have broader coverage on material thickness, diameter, joint configuration and welding positions. Similarly, ASME IX is more flexible on welder performance qualification requirements and accordingly a welder will have wider range of performance qualifications. When applied correctly, the use of ASME IX welding procedures often means significantly fewer welding procedures and welder performance qualifications are required for a given scope of work. Even though ASME IX qualified welding procedures have been widely used in pipeline facility and fabrication welding, it is not well understood on how to qualify the welding procedures in accordance with ASME IX and meet the additional requirements of the governing code or standard such as CSA Z662 in Canada. One significant consideration is that ASME IX refers to the construction code for the applicability of notch toughness requirements for welding procedure qualification, yet CSA Z662 and ASME B31.4 are both silent on notch toughness requirements for welding procedure qualification. This paper explains one preferred method to establish and develop an effective ASME IX welding procedure qualification program for pipeline facility and fabrication welding while ensuring suitability for use and appropriate notch toughness requirements. The paper discusses topics such as base material selection, welding process, welding consumable consideration and weld test acceptance criteria.


JOM ◽  
1965 ◽  
Vol 17 (9) ◽  
pp. 985-994
Author(s):  
E. H. Brubaker ◽  
J. D. Dennison ◽  
R. J. Eiber ◽  
A. B. Wilder

Author(s):  
Dante Campos ◽  
César Ortega ◽  
Jorge L. Alamilla ◽  
Alberto Soriano

This paper presents the definition of lower deck elevation (LDE) of fixed offshore platforms in Mexican part of the Gulf of Mexico (GoM), which were applied in the Mexican code for design and assessment of fixed offshore structures NRF-003-PEMEX-2007. This was obtained as a result of a decision methodology developed here, an optimization algorithm composed of an objective minimization function subject to a safety restriction and by the application of a set of real structural maintenance and equipment replacement costs. Platform projected service life dependent total costs of LDE contemplate expected costs of structural and equipment maintenance after the occurrence of tropical cyclones and northers, and the expected cost of equipment mobilization. This work regards a group of offshore platforms in the Bay of Campeche whose elevation lies between 15.85 and 19.10 m above mean sea level, as well as recent metocean hazard information. Similar expected values of total costs due to maintenance and repair were obtained, while safety constrains demand the LDE not to be less than +19.10 m.


The designer’s primary aims are avoidance of collapse and of unserviceability, generally through excessive deformation. These aims require knowledge of load extension characteristics. Structural strength depends on tangent modulus and deflexion on secant modulus so that premature departures from elasticity and proportionality are of importance. Definition of yield stress by the drop of beam method, while satisfactory for mild steel, may not be so for high yield materials particularly when structural stability is critical. The present definition of yield may have to be replaced by 0.2 % proof stress as has been common for light alloys. The influence of the limit of proportionality on structural strength has been observed in developing the design rules for plate girders for BS: 153, in the course of which tests undertaken on full-scale samples showed the proportional limit to be as low as 50 % of the nominal yield stress. The Tl steels in the U.S.A. exhibit major reduction in tangent modulus at about 85 % of their yield stress in compression.


1964 ◽  
Vol 1964 (116) ◽  
pp. 105-114
Author(s):  
Kazuo Terazawa ◽  
Midori Otani ◽  
Kiyoshi Terai ◽  
Fumiyoshi Kanatani

Tekstilec ◽  
2021 ◽  
Vol 64 (2) ◽  
pp. 136-148
Author(s):  
Nataliia Ostapenko ◽  
◽  
Marina Kolosnichenko ◽  
Larysa Tretiakova ◽  
Tatyana Lutsker ◽  
...  

A computational-experimental method of material selection for thermal protective clothing design is proposed in this article. The intended operating temperature of the garment lies within the range of 40−170 °С. The prereq¬uisite for the research was the lack of information regarding changes in the physical-mechanical and ergonomic characteristics of material assemblies during their use under high-temperature conditions. During the initial stage of research, there was a problem associated with the selection of the most important and the exclusion of the least significant indicators, in order to further reduce the number of experimental tests in laboratory and industrial conditions. The authors used the method of expert evaluations to solve the problems related to the selection of the most significant indicators for material assemblies. Material assemblies were formed by vary¬ing the combinations of heat-resistant, heat-insulation and lining layers of materials. Initial information for the proposed method was obtained from the experimental tests of sixteen material assemblies. According to the results of the ranking, the main parameters of material assemblies were identified as follows: the temperature range for which the use of clothing is intended, thickness, mass per unit density, rupture resistance, relative tear¬ing elongation, change in linear dimensions during mechanical loads, air permeability and change in assembly thickness during cyclic loads. It was established that the assembly that includes heat-resistant material of the Nomex comfort N.307 220 top, Nomex Serie 100 heat-insulation lining and Nomex TER 135 lining provides the necessary level of protection, reliability and ergonomics, and meets cost requirements.


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