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Houston, TX, United States
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Roche E.,SIS Technology Solutions LP | Summers A.,SIS Technology Solutions LP
Global Congress on Process Safety 2017 - Topical Conference at the 2017 AIChE Spring Meeting and 13th Global Congress on Process Safety | Year: 2017

A core attribute of all safeguards is that they must be functional against the loss event in question and one of the essential elements of functionality is speed. How to determine the response time available for a given safeguard to complete its action is a common project question. Several instrumentation and controls design pitfalls should be avoided when specifying the response time. A variety of engineering practices, from basic to advanced, may be used to justify the selected value. Among these are: · Expert judgment · Extrapolation · Mass and energy balance calculations · First principles process modeling Key technical issues include hardware response lags, process lags, application program delays, measurement error, and the design and safety margins. Careful attention to this specification is needed from the instrumentation and controls design team, for if an instrumented safeguard performs too slowly compared to the hazardous event, it provides no protection at all.


Jin H.,SIS Technology Solutions LP | Summers A.,SIS Technology Solutions LP
17th Process Plant Safety Symposium, PPSS 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety | Year: 2015

Risk analysis is an important tool to provide support for various risk management decisions in hazardous industries. For the last decade, the semi-quantitative Layers of Protection Analysis (LOPA) has been the dominating risk analysis technique in the US process industry. One basic assumption in LOPA is that all the protection layers are independent from each other and from the initiating cause; otherwise no risk reduction credit should be taken in the LOPA. However, many processes do have protection layers, which are dependent to some extent. For these systems, assuming independency may be too optimistic, whereas disregarding the partial risk reduction afforded from a partially dependent protection layer is pessimistic. In this paper, we consider processes with dependent protection layers (with a shared component), independent protection layers and pseudo-independent protection layers (subject to common cause failure). A long distance gas pipeline system is used as an example. By using reduced Event Trees for incident scenario modeling, Fault Trees for protection layers, and solving them in a coupled calculation, we show how protection layer dependencies are treated in risk analysis to obtain the overall risk reduction without being too optimistic or pessimistic.


Summers A.E.,SIS Technology Solutions LP | Hearn W.H.,SIS Technology Solutions LP
Process Safety Progress | Year: 2012

Risk analysis assesses the likelihood and consequence of events. The acceptability of the identified risk is determined by comparing it to a specified risk tolerance. The criteria applied depend on the analysis boundary, which may be the hazardous event or extend to the harm posed by the hazardous event. Risk analyses generally begin with a determination of the likelihood that the hazardous event occurs. This is where the process deviation exceeds the safe operating limit of the process resulting in loss of containment, release of hazardous materials, or other undesirable consequence. These analyses require estimation of the likelihood that the initiating event occurs and the probability that the proactive protection layers do not operate as required, allowing the hazardous event to occur. Reactive protection layers and conditional modifiers are considered when the analysis is evaluating the likelihood that harm is caused by the hazardous event. Various methods for performing risk analyses are discussed in several CCPS publications including Chemical Process Quantitative Risk Analysis [CCPS/AIChE, Guidelines for Chemical Process Quantitative Risk Analysis, 2000], Hazard Evaluation Procedures [CCPS/AIChE, Guidelines for Hazard Evaluation Procedures, 2008], and Layers of Protection Analysis [CCPS/AIChE, Layer of Protection Analysis: Simplified Process Risk Assessment, 2001]. However, the link between the selected risk criteria as described in Guidelines for Developing Quantitative Safety Risk Criteria [CCPS/AIChE, Guidelines for Developing Quantitative Safety Risk Criteria, 2009] and the factors considered in the analysis is not clearly described in these texts. Recognizing this opportunity, this article begins with a brief introduction to risk analysis concepts to provide a foundation for a discussion of the typical analysis boundaries and associated risk criteria. Then, it discusses how the analysis boundary and risk criteria affect the consideration of protection layers, enabling conditions, and conditional modifiers. © 2011 American Institute of Chemical Engineers (AIChE).


Hochleitner M.,SIS Technology Solutions LP | Roche E.,SIS Technology Solutions LP | Summers A.E.,SIS Technology Solutions LP
18th Process Plant Safety Symposium, PPSS 2016 - Topical Conference at the 2016 AIChE Spring Meeting and 12th Global Congress on Process Safety | Year: 2016

Some organizations invest thousands, sometimes millions, of dollars on automation systems in safety applications with the desire to minimize the risk of their enterprise. However, spending dollars does not mean that the plant will reach the desired degree of safety after implementation. Return on investment in safety controls, alarms, and interlocks (SCAI) can be negatively impacted by human error, such as inadequate design, installation, testing, maintenance, and operation of the automation systems. These human errors are systematic failures that can be reflected throughout a site. Organizational discipline and administrative controls are needed to identify and correct these failures. This paper will discuss important aspects of process safety management and how they are connected to the effectiveness of the SCAI. Functional safety auditing specifically looks at the management systems and procedures required to keep SCAI working effectively. The case studies presented will illustrate how safety system effectiveness could have been improved if a detailed audit of the SCAI documentation and performance records had been conducted and the findings addressed in a timely fashion. Copyright © 2016 Retained by Authors, April, UNPUBLISHED.


Summers A.E.,SIS Technology Solutions LP
3rd CCPS Latin American Process Safety Conference and Expo 2011 | Year: 2011

The concept of process safety management is well known throughout the world and relies on reducing risk continuously throughout the process life. The process equipment design and operation determine the limits of safe operation and the potential process hazards. It is the process engineer's responsibility to define a risk reduction strategy that addresses identified hazards, to develop and maintain the process safety information that supports this strategy, and to ensure operating procedures are available that result in timely and consistent execution of this strategy. This paper primarily focuses on how these activities apply to instrumented safety systems (ISS), as defined by CCPS Safe and Reliable Instrumented Protective Systems. It also identifies the unique requirements for safely instrumented systems (SISs) from IEC 61511.


Summers A.E.,SIS Technology Solutions LP
10th Process Plant Safety Symposium, Topical Conference at the 2008 AIChE Spring National Meeting | Year: 2014

A perfect process would have no hazards, but perfection is impossible in the real world. Latent conditions exist in the equipment, procedures, and personnel training, eventually presenting challenges to safe operation when enough accumulate. Safe operation is maintained through implementation of a risk reduction strategy relying on a wide variety of safety equipment practices to prevent releases of highly hazardous chemicals. Quality design and management are absolutely essential if real risk reduction and incident prevention is to be achieved - not just calculated risk reduction. This paper uses the Shewhart Cycle to introduce the various activities involved in achieving safe operation using instrumented safety systems (ISS). The paper follows the Plan, Do, Check, and Act process to discuss quality assurance and its application to ISS. Copyright © (2008) by the American Institute of Chemical Engineers.


Summers A.,SIS Technology Solutions LP
29th Center for Chemical Process Safety International Conference 2014, CCPS 2014 - Topical Conference at the 2014 AIChE Spring Meeting and 10th Global Congress on Process Safety | Year: 2014

Decision makers need reproducible, believable results to support investment decisions. A wide variety of hazard identification and risk analysis methods are available to support process safety decisions. All methods require knowledge in the fundamentals of process design and experience in the process operation under consideration. Every method has uncertainty and no method yields any better reflection of the risk than the level of engagement that the analyst or team has in the assessment. Traditional approaches work well on processes with a long history of operation, but are difficult to apply in the rapidly evolving environment of modem manufacturing. This paper discusses the challenges that the risk analysis process is facing in today's work environment. These challenges include advances in chemical manufacturing techniques, the rapid evolution of vogue practices, the focus on hazard scenarios, the false security of calculations, the rampant pace of technology change, and the increase in complexity of human and automation interaction. Copyright © (2014) by AIChE All rights reserved.


Mostia Jr. W.L.,SIS Technology Solutions LP
Proceedings of the Annual Symposium on Instrumentation for the Process Industries | Year: 2011

This paper describes a systematic program approach to reducing the risk of tower overfills in process units. This approach was taken on large project in a U.S. refinery which had embedded within its scope a program to reduce the risk due to tower overfill hazards. This program was tasked with analyzing and evaluating the risk due to tower overfills for 176 towers in over 25 operating units. This included consequence and severity identification, risk assessment, and identification of risk reduction means using Layer of Protection Analysis (LOPA) to reduce the tower overfill risk to the corporate risk reduction criteria. The program also identified the minimum tower instrumentation required for tower overfill protection. Each tower in the program was subject to a consequence based screening which identified and prioritized the towers for further analysis. Seven standard LOPA tower overfill scenarios were applied to each tower and project scope was identified based the LOPA recommendations.


Summers A.E.,SIS Technology Solutions LP | Hearn W.,SIS Technology Solutions LP
Journal of Loss Prevention in the Process Industries | Year: 2010

Overfills have resulted in significant process safety incidents. Longford (Australia, 1998), Texas City (United States, 2005), and Buncefield (United Kingdom, 2005) can be traced to loss of level control leading to high level and ultimately to loss of containment. A tower at Longford and a fractionating column at Texas City were overfilled, allowing liquid to pass to downstream equipment that was not designed to receive it. The Buncefield incident occurred when a terminal tank was overfilled releasing hydrocarbons through its conservation vents.The causes of overfill are easy to identify; however, the risk analysis is complicated by the combination of manual and automated actions often necessary to control level and to respond to abnormal level events. This paper provides a brief summary of the Longford, Texas City, and Buncefield incidents from an overfill perspective and highlights 5 common factors that contributed to making these incidents possible. Fortunately, while overfill can be a complex problem, the risk reduction strategy is surprisingly simple. © 2010 Elsevier Ltd.


Jin H.,SIS Technology Solutions LP | Summers A.,SIS Technology Solutions LP
Process Safety Progress | Year: 2016

Risk analysis is an important tool to provide support for various risk management decisions in hazardous industries. For the last decade, the semiquantitative Layers of Protection Analysis (LOPA) has been the dominating risk analysis technique in the US process industry. One basic assumption in LOPA is that all the protection layers are independent from each other and from the initiating cause; otherwise, no risk reduction credit should be taken in the LOPA. However, many processes do have protection layers, which are dependent to some extent. For these systems, assuming independency may be too optimistic, whereas disregarding the partial risk reduction afforded from a partially dependent protection layer is pessimistic. This article considers processes with dependent protection layers (with a shared component), independent protection layers, and pseudo-independent protection layers (subject to common cause failure). A long distance gas pipeline system is used as an example. Using reduced Event Trees for incident scenario modeling, Fault Trees for protection layers, and solving them in a coupled calculation, this article shows how protection layer dependencies are treated in risk analysis to obtain the overall risk reduction without being too optimistic or pessimistic. © 2015 American Institute of Chemical Engineers Process Saf Prog 35: 286–294, 2016. © 2015 American Institute of Chemical Engineers

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