Study on the Relief Capacity and Safety Integrity of Multiple Relief Valves of Charge Gas Pipe in Ethylene-Cracking Plant

2013 ◽  
Author(s):  
Jianxin Zhu ◽  
Xuedong Chen ◽  
YunRong Lu ◽  
Zhibin Ai ◽  
Weihe Guan
Keyword(s):  
Large Scale ◽  
Relief Valve ◽  
Pressure Relief ◽  
Emergency Relief ◽  
Safety Integrity Level ◽  
Upstream Pressure ◽  
Minimum Number ◽  
The Difference ◽  
Relief System

The shutdown of charge gas compressor in large-scale ethylene-cracking plant always involves emergency pressure relief of charge gas through multiple safety valves. The emergency relief capacity plays an important role on the safety of the overall plant. In this paper, by studying the difference between the configuration of the pressure relief system of two 1000 KTA ethylene-cracking plants (the inner diameters of the charge gas pipeline in both plants are 2m, while the number of same-sized relief valves are 28 and 19, respectively), the relief capacity of multiple relief valves is studied and compared with empirical calculation and numerical analysis. It is found that, due to the interruption of fluid flow when compressor is emergency shutdown, the upstream pressure of each relief valve increase steadily with the continuously make-up of the charge gas, but the difference between the inlet pressure of all relief valves can be neglected. With the increase of the upstream pressure, the opening of relief valves is determined mainly by the set pressure. In multiple valves pressure relief scenario, normally the downstream valves have greater relief capacity than those upstream valves if both relief valves have the same back pressure. Also, by analysis it is noted that the pressure relief capacities of multiple relief valves in both plants are sufficient. The minimum number of relief valves required for process safety is obtained. The maximum achievable Safety Integrity Level (SIL) of pressure relief system is determined by calculation of the reliability of the redundant relief valves. The analysis is used for determination of the SIL of the pressure relief system. The finding is also significant for determination of the required capacity of multiple relief valves.

scholarly journals Study on the Distribution Characteristics and Influencing Factors of Homocysteine in the Physical Examination Population

2021 ◽  
Author(s):  
Fang Bao ◽  
Ming Cui ◽  
Xiuying Shi ◽  
Shaoqing Ju ◽  
Hui Cong
Keyword(s):  
Blood Pressure ◽  
Physical Examination ◽  
Large Scale ◽  
Kidney Injury ◽  
Scientific Basis ◽  
Cerebrovascular Diseases ◽  
Health Examination ◽  
Significant Difference ◽  
The Difference

Abstract Background: Homocysteine (Hcy) is considered to be an independent risk factor for cardiovascular and cerebrovascular diseases. No study has evaluated the distribution of Hcy on a large-scale health examination. Accordingly, this study aimed to investigate the level and distribution of Hcy in the healthy physical examination population and the correlation with other biomarkers, and analyzed for cardiovascular and other diseases. The prevention provides an important scientific basis.Methods: From February 2017 to April 2020, 8063 medical examination populations were selected for analysis. Determination of serum Hcy, TC, TG, LDL-c, HDL-c, ALT, ALP, γ-GT, TBIL, GLU, urea, Cr, UA and related metabolic risk factors. According to the multivariate regression model of age, gender, smoking, drinking, body mass index (BMI), systolic blood pressure (SBP) and diastolic blood pressure (DBP), the relationship between Hcy and other biochemical indicators was evaluated. Results: Among 8063 cases, the age, BMI, SBP and DBP of the high-Hcy group were higher than those of the low-Hcy group, the difference was statistically significant (P<0.05), and the proportion of males, smoking and drinking were higher than the low In the Hcy group, the difference was statistically significant (P<0.05); the ALT, ALP, γ-GT, TBIL, Urea, Cr, UA, and TG in the high Hcy group were higher than those in the low Hcy group, and the difference was statistically significant (P<0.05 ); HDL-c in the high-Hcy group was lower than that in the low-Hcy group, and the difference was statistically significant (P<0.05). There was no statistically significant difference in TC, LDL-c, and GLU between the high- and low-Hcy groups (P>0.05). In multivariate analysis, lnHDL-C was negatively correlated with lnHcy (β=-0.038, SE=0.016, P<0.05), lnCr was positively correlated with lnHcy (β=0.055, SE=0.016, P<0.05), lnUA and lnHcy were positive correlation (β=0.043, SE=0.019, P<0.05). Conclusion: Hcy is closely related to HDL-c, Cr and UA, which indicates that Hcy may affect the metabolism of HDL-c and UA, and can also be used as an auxiliary diagnostic index for kidney injury.

The Effect of Reduced Design Margin on the Fire Survivability of ASME Code Propane Tanks

2004 ◽  
Author(s):  
A. M. Birk
Keyword(s):  
Pressure Vessels ◽  
Relief Valve ◽  
Pressure Relief ◽  
Mode Of Failure ◽  
Asme Code ◽  
Failure Scenario ◽  
Fill Level ◽  
Relief System ◽  
And Storage ◽  
Design Margin

The design margin on certain unfired pressure vessels has recently been reduced from 4.5 to 4.0 to 3.5. This has resulted in the manufacture of propane and LPG tanks with thinner walls. For example, some 500 gallon ASME code propane tanks have had the wall thickness reduced from 7.7 mm in 2001 to 7.1 mm in 2002 and now to 6.5 mm in 2004. This change significantly affects the fire survivability of these tanks. This paper presents both experimental and computational results that show the effect of this design change on tank fire survivability to fire impingement. The results show that for the same pressure relief valve setting, the thinner wall tanks are more likely to fail in a given fire situation. In severe fires, the thinner walled tanks will fail earlier. An earlier failure usually means the tank will fail with a higher fill level, because the pressure relief system has had less time to vent material from the tank. A higher liquid fill level at failure also means more energy is in the tank and this means the failure will be more violent. The worst failure scenario is known as a boiling liquid expanding vapour explosion (BLEVE) and this mode of failure is also more likely with the thinner walled tanks. The results of this work suggest that certain applications of pressure vessels such as propane transport and storage may require higher design margins than required by the ASME.

scholarly journals Quicker Measurement of Walls’ Thermal Resistance Following an Extension to ISO 9869 Average Method

2019 ◽  
Vol 111 ◽  
pp. 04019
Author(s):  
Arash Rasooli ◽  
Laure Itard
Keyword(s):  
Heat Flux ◽  
Thermal Resistance ◽  
Average Method ◽  
Large Scale ◽  
Accurate Determination ◽  
Acceptable Result ◽  
Heat Flux Meter ◽  
The Difference

Determination of the thermo-physical characteristics of the buildings’ components is crucial to illustrate their thermal behavior and therefore their energy consumption. Along the same line, accurate determination of the thermal resistance of the building walls falls into one the most important targets. Following the difference between in-lab, and on site thermal performance of walls, in-situ measurements have been highly recommended. The most well-known practice for in-situ measurement of walls’ thermal resistance is the Average Method of ISO 9869, using one heat flux meter and two thermocouples. The method, in comparison with other existing methods is quite straight-forward and therefore, is applied widely in large scale. Despite its simplicity, this method usually needs a relatively long time to reach an acceptable result. The current paper deals with a modification to the ISO 9869 method, making it in many situations much quicker than its original state. Through simulation of walls of different typologies, it is shown in which cases the measurement period becomes longer than expected. It is demonstrated how the addition of a heat flux meter to the aforementioned equipment can lead to a much quicker achievement of the thermal resistance, following the rest of the instructions of the standard method.

scholarly journals Asymptotic Optimality of Power-of-d Load Balancing in Large-Scale Systems

2020 ◽  
Vol 45 (4) ◽  
pp. 1535-1571 ◽  
Author(s):  
Debankur Mukherjee ◽  
Sem C. Borst ◽  
Johan S. H. van Leeuwaarden ◽  
Philip A. Whiting
Keyword(s):  
Large Scale ◽  
Asymptotic Optimality ◽  
Diffusion Limit ◽  
Fluid Limit ◽  
Large Scale Systems ◽  
Minimum Number ◽  
Join The Shortest Queue ◽  
The Difference ◽  
Shortest Queue ◽  
And Diffusion

We consider a system of N identical server pools and a single dispatcher in which tasks with unit-exponential service requirements arrive at rate [Formula: see text]. In order to optimize the experienced performance, the dispatcher aims to evenly distribute the tasks across the various server pools. Specifically, when a task arrives, the dispatcher assigns it to the server pool with the minimum number of tasks among d(N) randomly selected server pools. We construct a stochastic coupling to bound the difference in the system occupancy processes between the join-the-shortest-queue (JSQ) policy and a scheme with an arbitrary value of d(N). We use the coupling to derive the fluid limit in case [Formula: see text] and [Formula: see text] as [Formula: see text] along with the associated fixed point. The fluid limit turns out to be insensitive to the exact growth rate of d(N) and coincides with that for the JSQ policy. We further establish that the diffusion limit corresponds to that for the JSQ policy as well, as long as [Formula: see text], and characterize the common limiting diffusion process. These results indicate that the JSQ optimality can be preserved at the fluid and diffusion levels while reducing the overhead by nearly a factor O(N) and O([Formula: see text]), respectively.

Steady-State Positions of a Pop Action Safety Valve

2011 ◽  
Author(s):  
Jean-Franc¸ois Rit ◽  
Pierre Moussou ◽  
Christophe Teygeman
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
Relief Valve ◽  
Pressure Relief ◽  
Working Pressure ◽  
Process Industries ◽  
Water Pipes ◽  
Upstream Pressure ◽  
Pressure Relief Valves ◽  
The Stability

Pressure relief valves in water pipes are known to sometimes chatter when the inlet pressure slightly exceeds the maximum allowable working pressure (MAWP) value. Though these devices are responsible for numerous fatigue issues in process industries, there is a relatively low number of technical publications describing well-established facts about them, especially for heavy fluids. The present study deals with the investigation of the stability of a pressure relief valve when a pressure drop device is arranged upstream. The valve is a simple spring device, with a 1″1/2 inlet diameter and a set pressure equal to 3 MPa. The 12% to 66% range of relative opening for this valve exhibit an unstable static equilibrium of the plug, designed to achieve the so called “pop action”; as soon as the pressure set point is reached, a runaway process leads to the full opening. The statically stable regimes were observed in former studies with respect to the upstream pressure and to the plug position, with a test rig arrangement which ensured an almost constant pressure upstream. In the present study, high pressure drop devices are arranged upstream, in order to stabilize the hydraulic regimes. It is found that the upstream pressure drop devices significantly enlarge the range of steady state plug positions and upstream pressures. Pressure and plug position measurements are shown with a time resolution lower than 2 ms. Comparison with hydraulic regimes of the former studies indicate that the presence of an upstream pressure drop modifies the plug balance. It is proposed that the arrangement of pressure drop device upstream may significantly reduce the risk of valve instability in water pipes.

scholarly journals The Pressure Relief System Design for Industrial Reactors

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Iztok Hace
Keyword(s):  
System Design ◽  
Systems Design ◽  
Process Industry ◽  
Industrial Accidents ◽  
Pressure Relief ◽  
Blow Down ◽  
Emergency Relief ◽  
Industrial Plants ◽  
Ecological Problems ◽  
Relief System

A quick and simple approach for reactor—emergency relief system design—for runaway chemical reactions is presented. A cookbook for system sizing with all main characteristic dimensions and parameters is shown on one realistic example from process industry. System design was done based on existing theories, standards, and correlations obtained from the literature, which were implemented for presented case. A simple and effective method for emergency relief system is shown, which may serve as an example for similar systems design. Obtained results may contribute to better understanding of blow down system frequently used in industrial plants, for increasing safety, decreasing explosion damage, and alleviating the ecological problems together with environmental pollution in case of industrial accidents.

Justifying the Use of High Integrity Pressure Protection Systems (HIPPS)

2004 ◽  
Author(s):  
Edward M. Marszal ◽  
Kevin J. Mitchell
Keyword(s):  
Analytical Techniques ◽  
Chemical Plants ◽  
Pressure Relief ◽  
Emergency Relief ◽  
Body Of Knowledge ◽  
System A ◽  
Protection Systems ◽  
High Integrity ◽  
Petroleum Refineries ◽  
Relief System

As chemical plants and petroleum refineries plan for future expansion, the capability of existing pressure relief systems to safely dispose of higher capacities is often a significant constraint. Current codes and standards now allow for the use of High Integrity Pressure Protection Systems (HIPPS) in lieu of increasing the capacity of emergency relief systems. There is a significant body of knowledge on how to design a HIPPS system once the requirement for one has been established. However, there is gap in knowledge of what situations allow for HIPPS and what practical steps can be taken to determine when a HIPPS is justified. This paper describes the analytical techniques that can be used by engineers to justify a design using instrumented protection in lieu of upgrading the relief system. A review of applicable requirements from codes and standards is included along with risk-based methods to ensure a HIPPS design is as safe as — or safer than — conventional relief design.

Maximum Isentropic Flow of Dry Saturated Steam Through Pressure Relief Valves

1979 ◽  
Vol 101 (2) ◽  
pp. 113-117 ◽  
Author(s):  
L. Thompson ◽  
O. E. Buxton
Keyword(s):  
Flow Measurement ◽  
Maximum Flow ◽  
Saturated Steam ◽  
Relief Valve ◽  
Pressure Relief ◽  
Isentropic Flow ◽  
Property Data ◽  
Pressure Relief Valves ◽  
Significant Divergence ◽  
The Difference

The maximum isentropic flow of dry saturated steam using iterative computer techniques with standard (ASME) steam property data is determined. Comparison of this maximum flow with the Napier flow (the calibrating ideal flow for ASME pressure relief valve capacity ratings) reveals significant divergence between the two. A correction factor is developed to be applied to existing ASME safety and safety relief valve capacity ratings to rectify the difference. Experimental flow measurement work verifying the divergence between the maximum isentropic flow and the Napier flow is described.

scholarly journals Análise de RMS de 13C usando GIAO, CSGT e IGAIM: Fatores de escalonamentos de Terpenos

2020 ◽  
Author(s):  
Geomar Souza Alves ◽  
Fábio Luiz Paranhos Costa ◽  
Antônio Maia de Jesus Chaves Neto ◽  
Gunar Vingre da Silva Mota
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Scaling Factors ◽  
Interesting Point ◽  
X Ray Crystallography ◽  
Chemical Structures ◽  
Pcm Model ◽  
The Difference ◽  
Linear Regressions

Terpenes are natural products that have several biological and pharmacological properties that are directly related to their chemical structures. In the structural determination of organic molecules, Nuclear Magnetic Resonance (NMR) is used on a large scale. The chemical shift (δ) being the most important parameter. The present study aims to develop and test (the elemol molecule will be used for this purpose) δ scaling factors from 13C to terpenes, based on linear regressions. 10 complex sesquiterpene molecules were selected with the unmistakably determined structures (confirmed with X-ray crystallography). The geometries were optimized at the B3LYP / 6-311 + G (d, p) level, in the gaseous phase, and the δ will be obtained at the PBE0 / aug-cc-pvdz level with three different approaches GIAO, CSGT and IGAIM, in phase gaseous and liquid, where the PCM model (polarized continum model) was used. The TMS (tetramethylsilane) was used as a reference and the experimental data of 13C were obtained in chloroform. The results of scaled RMS for the terpenes used to generate the scaling factors show that when the effects of the solvent are taken into account, even implicitly, there is an improvement in the reproduction of experimental data. However, the difference in scaled RMS values is not large enough to justify taking into account interactions with the solvent, at least with the PCM model. It is interesting to note that with the level of theory PBE0 / aug-cc-pvdz, the GIAO method presented a lower performance than the other 2 used. Another interesting point is that its calculation time, according to the simulations generated in this work, was, on average, 30% greater than the CSGT and IGAIM. Thus, for studies with terpenes, with this level of theory, the use of the GIAO method is not indicated.

Assessment of Safety Integrity of LDPE Tubular Reactor With Emergency Pressure Relief Requirement Consideration

2011 ◽  
Author(s):  
Jianxin Zhu ◽  
Xuedong Chen ◽  
Zhibin Ai ◽  
Weihe Guan ◽  
Lijian Zhuang ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
State Of The Art ◽  
Tubular Reactor ◽  
Relief Valve ◽  
Pressure Relief ◽  
Medium Temperature ◽  
Emergency Relief ◽  
Ultra High Pressure ◽  
Highly Sensitive ◽  
Temperature And Pressure

The production of low density polyethylene (LDPE) with tubular reactor process always involves ultra high pressure (up to 310 MPa (3059 atm)) and medium temperature (normally less than 310°C (590 F)). As polymerization is highly sensitive to temperature and pressure fluctuation, emergency relief valves are required to prevent the runaway of a reaction (C2H4 decomposition, a strongly exothermal reaction). The pressure increase during decomposition develops rapidly (normally in several second). The pressure relief speed plays an important role in the safety integrity of reactor. The purpose of this paper is to demonstrate the evaluation of safety integrity of tubular reactor by taking process deviation and pressure relief requirement into consideration, and to determine the safety requirement specification of the emergency relief. A state of the art analysis is proposed in this paper. The time-dependent pressure fluctuation and relief capacity, as well as various decomposition scenarios during emergency pressure relief are studied. The analysis is then used to determine the required redundancy of the emergency relief valves. The probability of failure on demand (PFD) of multi-valve relief operation is calculated with the classic reliability model. The pressure fluctuation due to emergency pressure relief is calculated with a proven-in-use relief model. Necessary assumptions are made about the relief operation. It is concluded that 2 out of 5 (2005) emergency relief valves are sufficient for the emergency pressure relief in order to prevent the overpressurization of the tubular reactor under a given condition that the emergency relief valve fully opens in less than 3 seconds.

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