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Failure of Stainless-steel-based Components Used in an Oil Refinery – Analysis and Implications
• human – injuries, disease and loss of life; forgotten and hazards and deviations from safe operating procedures can
• environmental – environmental damage, pollution and injured/dead be accepted. Basically, people forget to be afraid, and this attitude is very
animals and plants; and dangerous.
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Defects, failures and accidents in refineries can cost millions
• economic – production loss, cost of repair and loss of process of dollars, can kill and injure hundreds of people and can harm the
equipment. environment for many years, so their implications must be considered in
the context of all of the factors previously described.
Risk is defined as the measure of a hazard that combines the measure of
its probability/frequency of occurrence with the measure of its various Summary
consequences. This means that risk can be tolerated or not depending on Stainless steels are widely used in the fabrication of components operating
various factors: the immediate or delayed effect of a hazard, the presence in the petrochemical industry for various reasons, mainly due to their
or absence of alternatives, the degree to which the risk is known, the excellent resistance to corrosion coupled with good mechanical
shared or personal character of the danger and the reversibility or properties. Nevertheless, some factors can lead to the failure of
irreversibility of the consequences.
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Therefore, there are three criteria for components, even if they are fabricated with an adequate material.
judging the tolerability of risk:
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In this article, three cases of failure of components made of stainless steel
• equity-based – individuals have the right of protection to certain were analysed. In the first case, the wear ring fractured due to hydrogen
levels/limits, and if these are surpassed, the risk is intolerable; embrittlement/stress corrosion, since the material used to make this
• cost–benefit – a comparison between the benefits of reducing risk and component had some characteristics that made it susceptible to failure
the costs of prevention; and when exposed to an H
2
S-, CO
2
- and chloride-rich environment. In the
• technology-based – satisfactory risk prevention is attained when good second case, the failure of a centrifugal pump shaft made of duplex
practices or updated technology are utilised. stainless steel occurred due to fatigue, probably caused by external factors
not related to the intrinsic characteristics of the material. In the third
Therefore, society accepts risks to which it is involuntarily exposed based case – the failure of a centrifugal pump axis made of austenitic stainless
on the benefit produced by the activity.
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In this context, the attitude of steel – the presence of sulphide inclusions contributed to fatigue fracture
the managers of the refineries towards risk is outstandingly important. In in this component despite adequate microstructure and hardness. The
most cases, the availability of financial resources plays an essential role in most viable method of prevention is the determination of inclusion
the decision of accepting the costs of risk prevention.
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Usually, less contents in stainless-steel samples. However, this procedure only indicates
financially successful organisations have fewer resources available for the problem; therefore, after the inspection corrections must be carried
operational demands such as preventative maintenance, inspection, out in the steel-making process in the subsequent production schedule.
training and replacement of ageing equipment; as such, poor financial
performance can contribute to the accidental release of hazardous These kinds of failure in refineries can have serious implications, related to
chemicals, which can result in serious damage to health and the three main aspects: human (injuries, disease and loss of life), environment
environment, as well as financial losses.
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(environmental damage, pollution and injured/dead animals and plants)
and economic (production loss, cost of repair and loss of process
Jones et al.
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state that most losses come from fixed equipment, such as equipment). Risk can be tolerated by society if the economic activity can
piping, vessels and heaters, rather than from rotating equipment. They render some benefits, but this tolerance is limited to some extent. The
also state that in the past reliability improvement was considered an availability of financial resources and the attitude of the managers of the
exclusive task of the maintenance team, but this has now changed: the refinery are essential factors that determine the success of risk prevention
participation of the operational team is considered essential to reduce actions, but the participation of the whole operational team, not just the
risks. In this sense, the participation of unions in the same task is maintenance team, including the participation of unions, cannot be
considered a very important factor.
23
According to Baker et al.,
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the price forgotten. Vigilance to prevent risk must be constant and people cannot
of reliability is constant vigilance. The passing of time without a process forget lessons, tasks and responsibilities, because the consequences of
accident is not necessarily an indication that all is well, and may contribute hazards in refineries can be disastrous. The passing of time without
to a dangerous and growing sense of complacency. Lessons can be hazards cannot be considered a guarantee against risk. ■
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HYDROCARBON WORLD VOLUME 4 ISSUE 1
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