Quest Consultants Inc.

Norman, OK, United States

Quest Consultants Inc.

Norman, OK, United States

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Marx J.D.,Quest Consultants Inc. | Nicotra A.,Bechtel Corporation
50th Annual Loss Prevention Symposium 2016, LPS 2016 - Topical Conference at the 2016 AIChE Spring Meeting and 12th Global Congress on Process Safety | Year: 2016

For several decades now, many consequence-based siting assessments (e.g., API RP 752) have relied upon a two-inch hole to represent what is termed a "credible release size" or a "maximum credible event" (MCE). Alternatively, a study may evaluate siting by use of a quantitative risk analysis (QRA), which would apply a full range of hole sizes. Due to QRA complexity and expense, the MCE analysis has often been the preferred approach for siting studies in the US, and the two-inch hole has been one of the more common choices for the MCE. Hole size choices range from small leaks (1/4-inch hole) through one-, two-, four-, and even six-inch holes. Why a two-inch hole? Does a two-inch hole provide a sufficiently accurate qualitative evaluation of risk? When a single hole size is chosen for a given purpose in a consequence analysis, that hole size should not be chosen based solely on engineering judgement, but should be based on more defensible information. This paper seeks to explain the basis for selecting the two-inch hole, including a literature review, concepts from consequence modeling, data from failure frequencies, and engineering judgement. Examples comparing the use of a single hole size (with emphasis on the 2-inch hole) to QRA results will also demonstrate some of the potential benefits and problems of an MCE analysis.


Denslow D.B.,Quest Consultants Inc. | Cornwell J.B.,Quest Consultants Inc.
18th Topical Conference on Refinery Processing 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety | Year: 2015

Accidental releases from LPG transport vessels and pipelines can cause devastating damage and loss of life. When a release occurs in equipment that handles LPG, the highly pressurized system can flash into vapor phase, causing a rapidly expanding flammable vapor cloud containing LPG vapor, air, and liquid LPG aerosol droplets. A release from isolated LPG vessels such as railcars and tanker trucks can cause a boiling liquid expanding vapor explosion (BLEVE). Due to the potential hazards associated with transport of LPG and the fuel's ever-increasing demand, it seems prudent to compare the risk associated with different forms of transportation of LPG. Consequence simulations are performed using CANARY by Quest® in order to model the effects of LPG releases from pipelines, tanker trucks, and railcars. The results of the consequence analysis are combined with accident, failure, and release frequency data for the specific equipment employed for each transportation method. The transportation risk associated with pipelines, railcars, and tanker trucks was evaluated with a quantitative risk analysis. The result shows that transporting LPG by pipeline has a significantly lower public risk than transporting LPG by railcar or tanker truck.


Marx J.D.,Quest Consultants Inc. | Werts K.M.,Quest Consultants Inc.
11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings | Year: 2011

The design and layout of new facilities can incorporate most of the principles and spacing requirements presented in API RP 752 with a basic consequence modeling study. However, many existing facilities are realizing that a basic consequence modeling study indicates major problems for onsite buildings when evaluating vapor cloud explosion impacts. The application of overpressure exceedance curves (OEC) represents a significant improvement to basing building siting solely on consequence analysis results. A discussion covers the construction of OEC for a typical hydrocarbon processing facility; benefits and potential problems; accounting for weather conditions, differing release sizes, and the specific layout of the facility; type of analysis that satisfies the requirements of API RP 752 for the explosion overpressure impact portion of an assessment; and the construction of OEC, which can be used to site temporary or portable buildings. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011).


Melton T.,Quest Consultants Inc. | Cornwell J.,Quest Consultants Inc. | Ishii B.,Quest Consultants Inc.
11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings | Year: 2011

With the release of the free, open source CFD Toolkit, OpenFOAM, modelers now have a powerful tool that allows them to model a wide range of situations and complex interactions in the chemical and petrochemical industries that were too expensive and time-consuming to model in the past. Quest's use of the OpenFOAM toolkit to model vapor cloud explosions in industrial settings was elucidated, including a comparison of results between validation studies and published experiments. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011).


Marx J.D.,Quest Consultants Inc. | Werts K.M.,Quest Consultants Inc.
Journal of Loss Prevention in the Process Industries | Year: 2013

The magnitude of damage due to a vapor cloud explosion can be estimated in many ways, ranging from look-up tables to quantitative risk analysis. An explosion overpressure analysis is a routine part of compliance with the American Petroleum Institute (API) Recommended Practice (RP) 752 when evaluating occupied buildings in a facility that processes flammable or reactive materials. In many cases, a risk-based approach is useful because consequence modeling studies often indicate major problems for buildings at existing facilities. One of the most common risk-based methods, overpressure exceedance, incorporates a wide range of potential explosion scenarios coupled with the probability of each event to develop the probability of exceeding a given overpressure at specific locations. But this and other methods that only use overpressure may not represent an accurate building response. By combining the risk-based methodology of the exceedance analysis with pressure and impulse data in the form of pressure-impulse (P-I) curves, a better measure of building damage can be generated. P-I curves for blast loading determination have been in use for decades, and allow the user to determine levels of damage based on a predicted overpressure and its corresponding impulse. Curves have been published for entire buildings, individual structural members, window breakage, and even consequences to humans. This paper will explore application of P-I curves for building damage, and will highlight some of the benefits, as well as some of the potential problems, of using P-I curves. © 2012 Elsevier Ltd.


Marx J.D.,Quest Consultants Inc. | Ishii B.R.,Quest Consultants Inc.
Process Safety Progress | Year: 2016

Facility siting studies have been a requirement for many years, specifically for facilities that must comply with OSHA's PSM program. Facility siting is frequently interpreted as performing a building siting study which adheres to the guidance given in API RP 752. Many of the siting studies conducted for large facilities over the past few decades have focused on explosion overpressure impacts to occupied buildings, with more simplistic evaluations for fire and toxic gas impacts. Toxic gas impact analyses often only evaluate the potential exposure of a building location, to a specific gas concentration, and do not evaluate the level of infiltration into the building where occupants may be impacted. Infiltration of flammable gases has largely been ignored in most building siting studies. Despite this oversight, this hazard is one which should be addressed when following the guidance found within API RP 752. Through the use of dispersion modeling and infiltration analyses, the hazards associated with flammable or toxic gas infiltration can be incorporated into a building siting study. This article outlines the process of conducting a building siting study in accordance with API RP 752, with specific emphasis on the consequence analysis for infiltration analyses. © 2016 American Institute of Chemical Engineers.


Marx J.D.,Quest Consultants Inc. | Werts K.M.,Quest Consultants Inc.
Journal of Loss Prevention in the Process Industries | Year: 2014

An explosion overpressure analysis is a routine part of compliance with the American Petroleum Institute (API) Recommended Practice (RP) 752 and 753. A basic consequence analysis often attempts to demonstrate a few scenarios that may appear to have the most extreme consequences; however, these scenarios may also have extremely low likelihoods of occurrence. To have a better understanding of how likely as well as how extreme a consequence may be, risk-based analysis is often required. One method used for this is an overpressure exceedance analysis which uses overpressure results from many potential explosion scenarios coupled with the probability of each scenario. Pressure-impulse curves can make better use of the explosion model's outputs (pressure and impulse) in order to predict building damage and possible impacts to personnel. Using this type of analysis with a building damage-fatality relationship, an F-N style curve can be created which shows the cumulative frequency vs. the number of potential fatalities. Generation of F-N curves can help to better define the risks to building occupants, provide an additional means of evaluating a building's acceptability, and can serve as a part of a quantitative risk analysis (QRA) for facility personnel. This paper will discuss the method used to predict the probabilities of building occupant fatalities for use in an F-N curve, as well as the benefits and potential problems with this type of analysis. © 2014 Elsevier Ltd.


Marx J.D.,Quest Consultants Inc. | Ishii B.R.,Quest Consultants Inc.
Journal of Loss Prevention in the Process Industries | Year: 2016

Facility siting studies are an important part of process safety, and are required for facilities that fall under OSHA's PSM program. Facility siting is frequently interpreted as performing a building siting study which adheres to the guidance given in API RP 752. Building siting may also consider siting of temporary or portable buildings based on the guidance in API RP 753. While both API RP 752 and API RP 753 provide a framework and some guidance for performing building siting studies, they do not provide detailed methodologies or provide guidance on performing a detailed analysis. As a result many building siting studies are inconsistent in their overall approach, or in the way they address hazards. Due to the recent scrutiny applied to building siting studies, more attention has been given to provide evaluations which correctly describe the range of hazards that may affect an occupied building at a petrochemical facility. This paper outlines a comprehensive methodology for performing building siting studies at such facilities. The methodology addresses the applicable hazards and the available tools by which the potential impacts to building occupants can be evaluated. © 2016 Elsevier Ltd.


Marx J.D.,Quest Consultants Inc. | Cornwell J.B.,Quest Consultants Inc.
10AIChE - 2010 AIChE Spring Meeting and 6th Global Congress on Process Safety | Year: 2010

As building siting studies become increasingly important for newly-designed facilities, the primary hazard is often vapor cloud explosion (VCE) overpressures. This is certainly true for LNG facilities, which typically do not have any acutely toxic materials. At these facilities, VCE and fires are the hazards that define the potential impacts, and the risk, to both onsite and offsite populations. While the approach for facility layout with regard to fires is generally straightforward and handled with fire protection measures, the approach for VCE modeling is not always clear. VCE modeling must demonstrate at what locations potential explosion impacts may affect offsite populations or onsite buildings. This is often accomplished using building damage levels which are correlated to the predictions of produced by a VCE model. Some of the challenges involved in using VCE modeling to predict explosion overpressures, specifically in regard to LNG facilities, are presented. Both import and export facilities are evaluated order to demonstrate the important issues with LNG projects. This is an abstract of a paper presented at the AIChE 2010 Spring National Meeting (San Antonio, TX 3/21-25/2010).

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