Design of Piping Systems for Accidental Explosion and Fire Events

Piping systems constitute the most critical portion of process plants. Proper blast and fire design of critical piping systems improve safety and resiliency. Design of piping and pipe supports are typically governed by operating and abnormal load conditions depending on the design basis. Well established analysis and design methodologies as per the applicable ASME codes ensure performance of piping systems against load cases such as internal pressure, thermal expansion, self-weight, wind, seismic and vibration. Pipe stress analysis using code based linear elastic analysis methods allow design for these types of conventional load cases in a practical way. However, beyond design basis load cases from hydrocarbon accidents including explosion and fires can pose additional challenges. Limitations of conventional design tools against demands due to extreme events require use of more advanced techniques. This study presents a practical approach for assessment and design of piping systems for hydrocarbon accident events. Performance based failure criteria for piping systems has been shown to reduce the conservatism compared to allowable stress design for extreme events. Examples from major projects and case studies are also presented to demonstrate the technical approach. Consideration of a holistic approach accounting for interaction of piping and its support structure plays a key role in improving the design process.

ANALISIS KEKUATAN STRUKTUR HYDRAULIC LIFTING MACHINE DENGAN MENGGUNAKAN METODE ELEMEN HINGGA

Hydraulic Lifting Machine merupakan jenis alat angkat yang didesain untuk memindahan barang ditempat yang relatif sempit. Dalam mendesain suatu alat selain fungsi dan kegunaannya kekuatan struktur merupakan salah satu aspek yang sangat penting untuk diperhatikan. Struktur tersebut haruslah mampu untuk menanggung beban yang timbul saat beroperasi dan memberikan keamanan bagi penggunanya dari kegagalan struktur. Oleh sebab itu tujuan dari penelitian ini adalah untuk menganalisis kekuatan struktur Hydraulic Lifting Machine dengan menggunakan metode elemen hingga. Berdasarkan hasil dari simulasi yang telah dilakukan dimana nilai tegangan resultan dan defleksi maksimum yang timbul pada struktur Hydraulic Lifting Machine yaitu pada beban kerja 100 kg tegangan resultannya sebesar 90,62 MPa dengan defleksi maksimum 4,39 mm, pada beban kerja 250 kg tegangan resultannya sebesar 218,51 MPa dengan defleksi 10,71 mm, pada beban kerja 500 kg tegangan resultannya sebesar 431,68 MPa dengan defleksi 21,25 mm, pada beban kerja 750 kg tegangan resultannya sebesar 644,84 MPa dengan defleksi 31,79 mm, dan pada beban kerja maksimal 1000 kg tegangan resultannya sebesar 858 MPa dengan defleksi 42,33 mm. Berdasarkan pada peraturan BS-5950 Structure Use of Steelwork in Building, nilai batas defleksi maksimumnya tidak boleh lebih dari 7,778 mm. Sedangkan untuk batas tegangan resultannya berdasarkan peraturan Allowable Stress Design (ASD) untuk dinyatakan aman adalah sebesar 149,7 MPa. Sehingga dapat disimpulkan bahwa struktur Hydraulic Lifting Machine layak digunakan dengan beban kerja maksimal 100 kg dengan angka safety factor 2,5. Kata kunci : Crane, Metode Elemen Hingga, Tegangan Von Mises.

Papua New Guinea Earthquake Proves the Value of Robust Pipeline Materials Selection and Construction

In 2018, the PNG LNG project sustained a Mw7.5 earthquake, and ca. 300 aftershocks, epicentered directly under key facilities. Around 150 km of high-pressure gas and condensate pipelines were affected. In anticipation of such an earthquake event and due to the challenging terrain that the pipeline traverses, two design methodologies were used in specifying the pipe and welds for the onshore pipelines: strain-based design and allowable stress design with robust materials selection. The strain-based design approach was used for segments crossing faults and was the subject of IPC2014-33550 [1]. In this paper, the robust allowable stress design that was used for the remainder of the onshore pipeline route will be discussed along with the performance of the pipeline designed with this methodology when it was subjected to the earthquake. Robust allowable stress design involved the selection of line pipe and welding procedures that would reduce the risk of failure during unanticipated ground movements. Lower grade, thicker wall pipe was selected, and enhanced weld properties were specified to increase weld strength overmatch and toughness. Additionally, enhanced testing of pipe and weld properties was performed in order to enable prediction of pipeline strain capacity and assessment of fitness for service of any portion of the pipeline that experienced longitudinal plastic strains due to ground movement. These efforts enabled the pipeline to safely sustain the ground movement experienced during the earthquake and allowed safe project operations to be rapidly restored. This paper provides details of the selection of pipe grade and wall thickness and the specification of material properties for pipe and girth welds. The property distributions achieved and the impact on strain capacity are presented along with estimates of the strain experienced by the pipeline due to the earthquake. The performance of the pipeline during the earthquake illustrate the benefits of the robust allowable stress design approach for pipelines in challenging environments.

nalisis Kuat Tarik Kayu Menggunakan PKKNI 1961 dan SNI 7973:2013

Use of wood construction in Indonesia is decrease significant than concrete and steel. While it is, government by National Standardization Corporation (BSN) had been published Indonesian National Standard about Wood Construction Design Spesification with code SNI 7973:2013. This code absolutly influential the old code which is PKKNI 1961. SNI 7973:2013 is regulate about Load esistance Factor Design (LRFD) and Allowable Stress Design (ASD), while PKKNI 1961 just use ASD method. In case SNI 7973:2013 have been use ASD, but it is different to PKKNI 1961. This research is would to find the different betwen SNI 7973:2013 and PKKNI 1961 to tension member with dimention 5/10, 6/12, 8/12 and 10/10. Result of research to tension member show that LRFD 100%, ASD 65,1% and PKKNI 111,4%.

Reliability-based versus allowable stress design of foundations for the Center for Missouri Studies building

Uncertainty in design parameters is inherent to the field of geotechnical engineering. Allowable stress design has conventionally been used for foundation design and accounts for uncertainty in geotechnical parameters and consequences of failure by assigning a global factor of safety. Allowable stress design is typically a conservative approach and may result in increased construction costs. The objective of the thesis is to compare allowable stress design with reliability-based design of foundations. The secondary objective is to initiate a 'living' database of geotechnical parameters for the University of Missouri - Columbia Campus, which will be expanded by future graduate students. A geologic history and site investigation results are presented to characterize subsurface conditions for the Center for Missouri Studies building in Columbia, Missouri and are entered into the geotechnical database. The existing foundation system of the Center for Missouri Studies building is evaluated using allowable stress design methods. The existing foundation system is reconsidered using reliability-based design. In a reliability-based design, uncertainty is quantified by evaluating the distribution of geotechnical strength parameters and structural loads. Two alternative foundation types are also considered. Reliability-based design was shown to be less conservative than allowable stress design. Both methods produced safe and reliable results, but foundation costs were reduced by seven (7) to thirty-five (35) percent when reliability-based design was used. The probability of failure of the foundations was acceptable from both design methods, but was unnecessarily conservative when using allowable stress design. A final objective of the thesis is to provide a template for future geotechnical engineering students to assemble an interactive geotechnical database and detailed subsurface profile for the University of Missouri-Columbia Campus. Appropriate use of the database and increased implementation of reliability-based design can reduce future design and construction costs of local foundations while assuring acceptable levels of reliability.

A probabilistic study on the geometrical design of gravity retaining walls

Purpose The purpose of this study is to introduce a relatively simple method of probabilistic analysis on the dimensions of gravity retaining walls which might lead to a more accurate understanding of failure. Considering the wall geometries in the case of allowable stress design, the probability of wall failure is not clearly defined. The available factor of safety may or may not be sufficient for the designed structure because of the inherent uncertainties in the geotechnical parameters. Moreover, two cases of correlated and uncorrelated geotechnical variables are considered to show how they affect the results. Design/methodology/approach This study is based on the failure and stability of gravity retaining walls which can be stated in three different modes of sliding, overturning and the foundation-bearing capacity failure. Each of these modes of failure might occur separately or simultaneously with a corresponding probability. Monte Carlo simulation and Taylor series method as two conventional methods of probability analysis are implemented, and the results of an assumed example are calculated and compared together. Findings The probability analysis of the failure in each mode is calculated separately and a global failure mode is introduced as the occurrence of three modes of sliding, overturning and foundation-bearing capacity failure. Results revealed that the global mode of failure can be used along with the allowable stress design to show the probability of the worst failure condition. Considering the performance and serviceability level of the retaining structure, the global failure mode can be used. Furthermore, the correlation of geotechnical variables seems to be relatively more dominant on the probability of global failure comparing to each mode of failure. Originality/value The introduced terminology of global mode of failure can be used to provide more information and confidence about the design of retaining structures. The resulted graphs maintain a thorough insight to choose the right dimensions based on the required level of safety.

Assessing the Target Reliability Index for Nuclear Piping

Previous research developed Load and Resistance Factor Design (LRFD) equations for Class 2 and 3 nuclear piping for different reliability levels and load combinations. The LRFD equations consider separate safety factors for each load and for the strength of steel in opposition to the Allowable Stress Design (ASD) equations used in the ASME Boiler and Pressure Vessel (B&PV) Code, Section III, Div. 1, where only one safety factor is considered. In order to use the developed LRFD equations for the design of nuclear piping, specific reliability levels or else acceptable probabilities of failure need to be assigned to each Code equation. The paper discusses the available methods for evaluating the target reliability index, such as historical data of piping failures, expert-opinion elicitation, and Code calibration. Code calibration is the method of determining the existing level of reliability in the Code equations and assigning the same reliability to the developed LRFD equations in a consistent manner. Code Calibration is explained to be the more appropriate method of assigning reliability levels to the LRFD equations. The other methods can supplement the analysis results.

A Study of Axial Compression in the ASME B&PV Code for Pipe Supports and Restraints

Axial compression allowable stress for pipe supports and restraints based on linear elastic analysis is detailed in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF. The axial compression design by analysis equations within NF-3300 is replicated from the American Institute of Steel Construction (AISC) using the Allowable Stress Design (ASD) Method which was first published in the ASME Code in 1973. Although the ASME Boiler and Pressure Vessel Code is an international code, these equations are not familiar to many users outside the American Industry. For those unfamiliar with the allowable stress equations, the equations do not simply address the elastic buckling of a support or restraint which may occur when the slenderness ratio of the pipe support or restraint is relatively large, however, the allowable stress equations address each aspect of stability which encompasses the phenomena of elastic buckling and yielding of a pipe support or restraint. As a result, discussion of the axial compression allowable stresses provides much insight of how the equations have evolved over the last forty years and how they could be refined.

A Study of Axial Compression in the ASME B&PV Code for Pipe Supports and Restraints

Axial compression allowable stress for pipe supports and restraints based on linear elastic analysis is detailed in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF. The axial compression design by analysis equations within NF-3300 are replicated from the American Institute of Steel Construction (AISC) using the Allowable Stress Design (ASD) Method which were first published in the ASME Code in 1973. Although the ASME Boiler and Pressure Vessel Code is an international code, these equations are not familiar to many users outside the American Industry. For those unfamiliar with the allowable stress equations, the equations do not simply address the elastic buckling of a support or restraint which may occur when the slenderness ratio of the pipe support or restraint is relatively large, however, the allowable stress equations address each aspect of stability which encompasses the phenomena of elastic buckling and yielding of a pipe support or restraint. As a result, discussion of the axial compression allowable stresses provides much insight of how the equations have evolved over the last forty years and how they could be refined.

Seismic Assessment of Petrochemical Piping Systems Using a Performance-Based Approach

The need of enhanced seismic analysis and design rules for petrochemical piping systems is widely recognized, where the allowable stress design method is still the customary practice. This paper presents an up-to-date performance-based seismic analysis (PBSA) of piping systems. The concept of performance-based analysis is introduced and a link between limit states and earthquake levels is proposed, exemplifying international code prescriptions. A brief review on seismic design criteria of piping systems is then provided by identifying the main critical issues. Finally, the actual application of the performance-based approach is illustrated through nonlinear seismic analyses of two realistic petrochemical piping systems.