640 publications from this institution
Quantified risk analysis (QRA) was used for the revision of regulatory separation distances associated with medium size liquefied petroleum gas (LPG) refuelling facilities used in automotive service (gas) stations. Typically these facilities consist of a 7.5kl pressure vessel, pump, pipework, dispensing equipment and safety equipment. Multi-tank installations are relatively uncommon. This paper describes the hazard scenarios considered, the risk analysis procedure and the selection and application of data for initiating events and for rates of failure of mechanical components and of the pressure vessel. Human errors and intervention possibilities were also considered. Because of the inapplicability of established consequence models and the relatively small scale of the facilities, a number of tests were performed to estimate flame length, flame impingement effects, ignition probabilities and the effectiveness of screening devices.
The relatively limited data for the corrosion and pitting of high nickel alloys are reviewed herein and time-dependent trends developed for exposures in marine and atmospheric environments. Data sets for average or ‘uniform’ corrosion losses that are sufficiently extensive show topological consistency with the bimodal functional model previously observed for steels and various copper-nickel and aluminum alloys. Trends for localized corrosion (pit or crevice depth) plateau after earlier rapid growth over several years. The present observations add support to the concept that there is a change in corrosion behavior with extended temporal exposure and that this is generally consistent for many alloys. They also reinforce that shorter-term observations of maximum corrosion or pit depth usually is unsuited for extrapolation to, and prediction of, longer-term corrosion as typically important for practical infrastructure applications.
No abstract is provided for this article.
Many extensive atmospheric corrosivity surveys have been undertaken covering cities, regional areas and sometimes countries in order to plot corrosion maps and identify possible sources of higher infrastructure risk. Classically, the surveys employ mild steel, copper steel and/or zinc coupons and corrosivity is derived by determining mass loss of the exposed specimens. Higher areas of corrosion loss are generally ascribed to airborne chlorides from marine sources and/or sulphur and nitrogen compounds from industrial fallout. Bacterial influence on corrosion has been well documented in buried and marine conditions and more recently recognized as a major factor in tidal conditions notably as accelerated low water corrosion. Hence it follows that if bacteria play a part in immersed, tidal and buried conditions, they should also be involved with atmospheric corrosion. To elucidate this hypothesis a trial has been designed and implemented in which mild steel coupons have been deployed in ten different environments to monitor the effect of airborne compounds. Chlorides, nitrogen and sulphur compounds can be considered as pollutants but equally can be thought of as essential nutrients for bacterial growth. Locations have been chosen ranging from extreme to moderate for chloride deposition and for differing particulate nitrous and sulphur compounds. In addition, a sub-alpine and a desert environment far removed from contamination are part of the project. The present paper reports the results for mass losses and corrosion products in the first year of exposure and compares these observations with material already available in the literature.
Novel observations of changes in pitting morphology of 6060 aluminum alloys immersed for periods of 3 y, 3.5 y, and 4 y in temperate seawater are reported. They indicate that the initiation and propagation of pitting involve several different mechanisms. These result in small (semi-) hemispherical pits, irregular polygonal-shaped larger pits, and also extremely large and deep pits with complex morphologies. Principally intergranular corrosion and crystallographic pitting were observed. It is proposed that the changing nature of the pit morphologies is associated with the accumulated corrosion products and, to a lesser extent, affected by the marine growth attached to the metal surface.
Chains usually form the upper part of moorings systems used for maritime structures such as floating production storage and offloading (FPSO) vessels, increasingly employed in the offshore oil and gas industry particularly in very deep waters. Current design rules do not differentiate between corrosion and inter-link wear. Laboratory experiments are described to determine the rate of wear of model (i.e. small-scale) mooring chains for up to 200,000 wear cycles. Various axial loadings and specific angular displacement were used with testing under either dry or wet conditions and for un-corroded and corroded chain. The results show that tensile force has a significant but non-linear effect on the inter-link wear. The amount of wear is similar for un-corroded and for corroded chains and is lower in wet conditions.
No abstract is provided for this article.
Comprehensive data are presented for corrosion losses of mild steel exposed for up to 5 years, all obtained from exposing steel coupons at one specific severe marine exposure site on the Pacific Ocean coast. The test programme considered the effects of duration of exposure, inclination, orientation, height, shielding, and coupon variability, using multiple, nominally identical mild steel coupons, all under a single local climatic regime. Such a controlled, consistent, natural environment permits unique, valid comparison of the various influences, both for short-term and longer-term exposures, unlike previous tests of some parameters conducted in the short term at disparate sites. In contrast to coupons exposed only on one side, boldly exposed double-sided coupons corroded severely within 3 years. The effects on corrosion behaviour between individual coupons exposed at different heights and vertical continuous single strips of steel are described. Also reported are corrosion losses for continuous strips and for a series of coupons oriented in different directions. Observations of variability in corrosion losses for nominally identically exposed steel coupons are reported. The effect on corrosion losses with continued exposure to 5 years is reported and compared with information available in the literature.
No abstract is provided for this article.
The 45 year old Sorell Causeway Bridge was demolished in 2002 due to concerns regarding the corrosion of prestressed tendons. Three beams of varying condition were salvaged from the demolition process and were relocated to the Structural Laboratory at the University of Newcastle. The beams were examined for load capacity and load deflection behaviour, as well as being subject to very detailed investigations. This paper provides the first set of findings from initial investigations carried out in November-December 2005, in particular providing comment on the load characteristics of the beams and instances of corrosion observed. (a) For the covering entry of this conference, please see ITRD abstract no. E214936.
No abstract is provided for this article.
No abstract is provided for this article.
It is common practice in atmospheric corrosion to fit the power-law function as a 'model' to help predict longer term corrosion loss or maximum pit depth. This function is also known as the 'log-log model' since it plots as a straight line on log-log paper. It used extensively including for aluminium alloys. A review of the relatively few data sets for long-term corrosion of aluminium shows systematic variation from the log-log power law model. Instead, in many cases the data can be interpreted as consistent with the multi-phase model previously proposed for steel corrosion in marine exposure conditions. Consideration is given to why the multi-phase model appears to be applicable also to long-term corrosion of aluminium alloys. This includes the important effect of corrosion products on oxygen diffusion, even though corrosion products of aluminium tend to occur in localized areas, that almost always involves pitting rather than general or uniform corrosion. It is proposed that the build-up of corrosion products forces a change to the chemical reactions responsible for aluminium corrosion, specifically forcing a change from cathodic oxidation and polarization in the shorter term to cathodic hydrogen reduction and polarization in the longer-term. The greater possible rate of outward diffusion of hydrogen compared to inward diffusion of oxygen is primarily responsible for the bi-modal character of corrosion loss or maximum pit depth as a function of exposure time.
In the classical theory of thermoelastic solids, the deflection of linearly elastic isotropic bodies as a result of applied thermal loads can be determined using Maisel's Integral Solution, a technique based on Betti's Reciprocal Theorem. It is a requirement of the technique that a solution to the isothermal equivalent linear elastic stress distribution problem is available. In the conventional structural analysis of linearly elastic structures, a particular adaptation of the virtual work method, known as the unit (dummy) load technique, may be used to obtain structure deflections. It has recently been shown that this technique can be adapted for the solution of hyperstatic structures where the hyperstatic stress distribution due to applied loading is not known. It will be shown that these approaches to deflection calculation are essentially equivalent, and that the application of either technique can considerably simplify deflection calculations for hyperstatic structures subject to temperature differentials.
Mild and low alloy steels are used extensively for off-shore structures and for ship construction as well as for sheet piling and harbour-side facilities. Despite more than 60 years of effort, and some quite extensive, long term experimental test programs, the precise understanding of the mechanics of the marine corrosion of these steels and the influences of the various factors which are now known to be important has been slow to develop and, in the context of mathematical formulation, have been neglected by material scientists/engineers. The various factors of importance in marine corrosion and the models which have been proposed to describe time-dependent material loss as a function of time are reviewed.
Previous work by the author has focused on some of the physical and practical issues of short term electrochemical testing of soils. This work has shown that electrochemical testing is valid and the results reproducible for soils. The technique can measure short-term corrosion rates and gives an insight to the different corrosion mechanisms present in an underground environment. What has not yet been well demonstrated using this electrochemical cell is whether short-term electrochemical testing relates to long-term field corrosion, particularly pitting corrosion. A successful correlation between short term corrosion testing and long-term field corrosion would give the asset owner access to a valuable predictive tool. The purpose of this paper is to critically examine the theory behind this commonly applied industry test and present some initial results of experimental testing undertaken as part of this current research. Over the past 5 years, as part of an ongoing condition assessment program, Hunter Water Australia has been collecting long-term field pipe corrosion data, and associated soil samples, for buried cast iron pipelines within the Hunter region. Various individual pipes were sandblasted and the corrosion data recorded. At each site a representative soil sample was collected for the purpose of assessment using the electrochemical test described previously (Dafter 2009). This sampling and testing program has provided an opportunity for long-term field pipe corrosion to be directly compared with short-term electrochemical tests. This paper provides a description of the short-term testing and long-term field corrosion recording that has been undertaken through this research program to date, and includes a discussion of the results of electrochemical testing that have been achieved.
The reliability analysis of multi-membered structural systems such as steel tubular offshore platforms has proved to be a challenging task, and one on which increasing interest is being focussed. The modelling of applied wave loading for such structures is reviewed herein, together with appropriate statistical models. For the structural analysis in reliability theory work, a single wave load system only has been most commonly considered. Real wave trains, however reach the various structural components at different times and this may have an effect on the sequence of most likely member failure. This can, in turn, affect the calculated probability of failure for the structure as a whole, as is demonstrated in the paper for a reasonably realistic but idealized offshore structure.
