Hazardous Leaks Research Articles

A straightforward strategy for leak localization in two-phase gas pipelines

The leak localization (LL) functionality is an important piece of leak detection systems that continuously monitor the operation of pipelines in real-time. After a leak is detected, it must be located as soon as possible so that mitigating actions can be taken to remedy the undesirable hazardous leak consequences. The most popular methodology used to locate leaks in single-phase pipelines is based on the pressure-gradient along the line. This technique uses the SCADA data polled and collected at the ends of the line segment, along with a fluid dynamics mechanical model capable of describing the flow in steady-state, to infer the leak position. By using the flow data at the pipe ends, the LL methodology seeks the interception of the pressure gradients computed by marching forward and backward along the line to estimate the leak site. This paper presents a detailed study to extend the LL strategy based on the pressure-gradient to two-phase flows in gas pipelines. To achieve this goal, without appealing to field or experimental data, we have built a leak database for typical real-world two-phase gas pipelines under the stratified-pattern flow by means of numerical simulations. By using a transient four-equation single-pressure two-fluid model, with suitable source terms to account for the leak existence, numerical simulations emulating leaks in a pipeline were carried out using the Flux-Corrected Transport method. After being validated by the commercial simulator OLGA, the mathematical model was employed to generate a leak database contemplating leaks of three different magnitudes at three distinct locations along the line for two different scenarios considering low and high holdup contents. The performance of the LL strategy, which has used as mechanical model the steady-state parcel of the transient mathematical model described above along with the simulated data at the pipe inlet and outlet, was evaluated by computing the leak location relative errors. The obtained results have shown that the pressure-gradient methodology has presented a particularly good performance under the circumstances considered herein. It was able to locate leaks of magnitudes between 1% and 10% of the total mass flowrate at the pipe inlet with relative errors ranging from 0.26% to 10.0%.

Aluminum-air battery with cotton substrate: Controlling the discharge capacity by electrolyte pre-deposition

Conventional Al-air battery has many disadvantages for miniwatt applications, such as the complex water management, bulky electrolyte storage and potential leakage hazard. Moreover, the self-corrosion of Al anode continues even when the electrolyte flow is stopped, leading to great Al waste. To tackle these issues, an innovative cotton-based aluminum-air battery is developed in this study. Instead of flowing alkaline solution, cotton substrate pre-deposited with solid alkaline is used, together with a small water reservoir to continuously wet the cotton and dissolve the alkaline in-situ. In this manner, the battery can be mechanically recharged by replacing the cotton substrate and refilling the water reservoir, while the thick aluminum anode can be reused for tens of times until complete consumption. The cotton substrate shows excellent ability for the storage and transportation of alkaline electrolyte, leading to a high peak power density of 73 mW cm−2 and a high specific energy of 930 mW h g−1. Moreover, the battery discharge capacity is found to be linear to the loading of pre-deposited alkaline, so that it can be precisely controlled according to the mission profile to avoid Al waste. Finally, a two-cell battery pack with common water reservoir is developed, which can provide a voltage of 2.7 V and a power output of 223.8 mW. With further scaling-up and stacking, this cotton-based Al-air battery system with low cost and high energy density is very promising for recharging miniwatt electronics in the outdoor environment.

A new approach for accurate detection of leakage paths from multiple-wenner arrays inverted resistivity imaging in embankment dam

Aiming at the difference of hidden danger identification of embankment dams by different arrays of high-density electrical method, a combined inversion method of wenner data volume is proposed to improve the resolution capability of target. The response characteristics of α, β and γ array to the preset model are presented by constructing the geoelectric model of the dam body and the potential leakage hazard in the contact zone. According to the simulation results, different arrays have different detection effects on the same target and the same array has different detection effects on different targets. β array reflects better effect of low resistance area, and γ array is more suitable for dividing dam body boundary, but both have weak anti-interference ability. In addition, the spatial feature information of the target by multiple-wenner inversion is more for the preset model and can effectively compensate for the limitation of a single array. The inversion results based on a priori model can suppress boundary interference and improve the effective identification of preset hidden dangers and boundary. The field test also shows that the anomaly determined by multiple-wenner inversion technology is highly consistent with the leakage site, which effectively improves the accuracy of hidden danger diagnosis.

Estimating natural gas emissions from underground pipelines using surface concentration measurements☆

Rapid response to underground natural gas leaks could mitigate methane emissions and reduce risks to the environment, human health and safety. Identification of large, potentially hazardous leaks could have environmental and safety benefits, including improved prioritization of response efforts and enhanced understanding of relative climate impacts of emission point sources. However, quantitative estimation of underground leakage rates remains challenging, considering the complex nature of methane transport processes. We demonstrate a novel method for estimating underground leak rates based on controlled underground natural gas release experiments at the field scale. The proposed method is based on incorporation of easily measurable field parameters into a dimensionless concentration number, ε, which considers soil and fluid characteristics. A series of field experiments was conducted to evaluate the relationship between the underground leakage rate and surface methane concentration data over varying soil and pipeline conditions. Peak surface methane concentrations increased with leakage rate, while surface concentrations consistently decreased exponentially with distance from the source. Deviations between the estimated and actual leakage rates ranged from 9% to 33%. A numerical modeling study was carried out by the TOUGH3 simulator to further evaluate how leak rate and subsurface methane transport processes affect the resulting methane surface profile. These findings show that the proposed leak rate estimation method may be useful for prioritizing leak repair, and warrant broader field-scale method validation studies. A method was developed to estimate fugitive emission rates from underground natural gas pipeline leaks. The method could be applied across a range of soil and surface covering conditions.

Prevention of Gas Leakage Hazards in Home

Prevention of Gas Leakage Hazards in Home

Influencing factors of the chain effect of spherical gas cloud explosion

Flammable gases and liquids are widely used in industry and have serious leakage hazards. When a leaking gas cloud accidentally encounters an ignition source, it results in vapor cloud explosion accidents and multiple explosions. Pressure and flow field monitoring of a primary exploding spherical gas cloud and the secondary explosion of the gas cloud were conducted using the pressure acquisition system and schlieren system, and the impact of different influencing factors on exploding were analyzed. It was found that the larger the size of the primary exploding gas cloud, the smaller the distance between the primary exploding gas cloud and the secondary explosion gas cloud, and the larger the explosion intensity of the two gas clouds. Ignition on both sides of the primary exploding gas cloud was more likely to cause a blasting effect than was central ignition. The change in sparking ignition energy had no obvious effect on explosion propagation. When multiple gas clouds were exploding, the position of the primary exploding gas cloud had a considerable influence on the chain effect of exploding. If the primary exploding gas cloud was located in the middle of multiple gas clouds, interaction occurred between the primary exploding spherical gas cloud and the secondary explosion gas cloud because the angle formed by the secondary explosion gas cloud decreased, and the explosive intensity of the exploding gas cloud was higher. When the primary exploding gas cloud was on the side, the smaller the angle, the closer the lateral gas cloud was to the flame development path of the explosive gas cloud, which increased the likelihood of a blast and increased explosion intensity.

Numerical and experimental study on the generation and propagation of negative wave in high-pressure gas pipeline leakage

Negative-wave-based leakage detection and localization technology has been widely used in the pipeline system to diminish leak loss and enhance environmental protection from hazardous leak events. However, the fluid mechanics behind the negative wave method has yet been disclosed. The objective of this paper is to investigate the generation and propagation of negative wave in high-pressure pipeline leakage. A three-dimensional computational fluid dynamic (CFD) study on the negative wave was carried out with large eddy simulation (LES) method. Experimentally validated simulation presented the transient wave generation at the leak onset and the comprehensive wave evolution afterwards. Negative wave was proven to be a kind of rarefaction acoustic waves induced by transient mass loss at the onset of leakage. Diffusion due to the density difference at wave fronts drives the negative wave propagation. Propagation of negative wave can be categorized into three states – semi-spherical wave, wave superposition and plane wave, based on different wave forms. The wave characteristics at different states were elucidated and the attenuation effects were discussed respectively. Finally, a non-dimensional correlation was proposed to predict the negative wave amplitude based on pipeline pressure and leak diameter.

The environmental and safety performance of gas utilities in the United States

The performance of energy service providers has important environmental and safety consequences in local communities. This paper uses a novel dataset compiled from operator reports and infrastructure monitoring data obtained from three different US federal agencies to assess the performance of retail gas utilities nationwide in terms of addressing gas leaks and minimizing leaked volume. Our panel data set includes yearly observations for 727 retail gas utilities from 2009 to 2017. We show that safety hazards and environmental costs of gas leaks are widespread across providers that vary in terms of ownership, size, and region. We then use a series of Bayesian hierarchical models to regress four outcome variables—hazardous leaks, end-year unfixed leaks, total gas volume leaked, and significant incidents—on infrastructure conditions, regional service context, and socio-economic service population characteristics. Unlike what is observed in other critical infrastructure cases such as drinking water, socio-economic conditions are not strongly predictive of service outcomes. Additionally, public utilities exhibit better environmental performance on average, and no difference in maintenance backlogs. Because the environmental costs of poor performance--primarily in terms of methane greenhouse gas emissions--are predominantly social, policy tools such as consolidation and privatization are unlikely to improve environmental outcomes.

Simulation the Probability of Liberalizing Chlorin Gas from Urban Water Chlorination System in Alborz: With the Cancer Approach

Background: Qazvin province has suffered a lot of natural disasters (earthquakes) for a long time. so, the establishment of the first industrial city in Iran, has always been a source of concern. One of these problems is the possibility of chlorine gas leaking from the chlorination system of drinking water and treatment plant the existing ones are on the health of the inhabitants of this region.
 Material and method: This analytical study was carried out in Novorossiysk district of Alborz in December 2012. Initially, chlorine gas leakage scenarios from these facilities were simulated by ALOHA and WISER software, and then using the Emergency Level System, according to the CCPS Consultative Center's Chemical Process Safety Advice, the Emergency Response Program was presented.
 Results: ALOHA software, in comparison with WISER software, has more precision to identify and address the consequences of chlorine gas leakage hazards and according to the simulation of this software in the event of a leak from the well and water resources unit at 8240 m from the area and at night 7520 meters will be affected. Due to the speed of delivering results through the WISER software, this software can be used at times when the operating speed is considered (incident time).
 Conclusion: According to the CCPS model, the emergency conditions were classified at levels 3 and 4, therefore, the relevant crisis management agencies (Qazvin Crisis Management Committee, Alborz City Health Center, Red Crescent and Firefighting Authority) should provide training maneuvers At Alborz city level, and informing people of cities and industrial companies, many efforts have been made to reduce human and environmental damage in case of possible leakage.

Simulation the Probability of Liberalizing Chlorin Gas from Urban Water Chlorination System in Alborz: With the Cancer Approach

Background: Qazvin province has suffered a lot of natural disasters (earthquakes) for a long time. so, the establishment of the first industrial city in Iran, has always been a source of concern. One of these problems is the possibility of chlorine gas leaking from the chlorination system of drinking water and treatment plant the existing ones are on the health of the inhabitants of this region.
 Material and method: This analytical study was carried out in Novorossiysk district of Alborz in December 2012. Initially, chlorine gas leakage scenarios from these facilities were simulated by ALOHA and WISER software, and then using the Emergency Level System, according to the CCPS Consultative Center's Chemical Process Safety Advice, the Emergency Response Program was presented.
 Results: ALOHA software, in comparison with WISER software, has more precision to identify and address the consequences of chlorine gas leakage hazards and according to the simulation of this software in the event of a leak from the well and water resources unit at 8240 m from the area and at night 7520 meters will be affected. Due to the speed of delivering results through the WISER software, this software can be used at times when the operating speed is considered (incident time).
 Conclusion: According to the CCPS model, the emergency conditions were classified at levels 3 and 4, therefore, the relevant crisis management agencies (Qazvin Crisis Management Committee, Alborz City Health Center, Red Crescent and Firefighting Authority) should provide training maneuvers At Alborz city level, and informing people of cities and industrial companies, many efforts have been made to reduce human and environmental damage in case of possible leakage.

Low-cost Al-air batteries with paper-based solid electrolyte

Abstract This work demonstrates a novel-type paper-based solid electrolyte (PBSE) and its application in Al-air battery, which is targeted for miniwatt applications. Benefited from the solid-form electrolyte, a liquid-free operation of the Al-air battery is realized, eliminating the potential leakage hazard and therefore improving the battery practicability. The PBSE is prepared by impregnating gel electrolyte into porous cellulose paper, followed by a solution casting process to solidify the gel. The as-prepared PBSE can either be used in mechanical rechargeable Al-air batteries, or be integrated into single-use flexible Al-air batteries. Currently the PBSE can achieve a moderate battery performance with a peak power density of 3.8 mW cm-2 and an Al specific capacity of 900.8 mA h g-1. Properties of the PBSE can be further improved by a comprehensive parametric study on its fabrication parameters, such as gel concentration, casting temperature, casting time, porosity and pore size of paper substrate, etc.

Assessment on the leakage hazard of landfill leachate using three-dimensional excitation-emission fluorescence and parallel factor analysis method

A large number of simple and informal landfills exist in developing countries, which pose as tremendous soil and groundwater pollution threats. Early warning and monitoring of landfill leachate pollution status is of great importance. However, there is a shortage of affordable and effective tools and methods. In this study, a soil column experiment was performed to simulate the pollution status of leachate using three-dimensional excitation-emission fluorescence (3D-EEMF) and parallel factor analysis (PARAFAC) models. Sum of squared residuals (SSR) and principal component analysis (PCA) were used to determine the optimal components for PARAFAC. A one-way analysis of variance showed that the component scores of the soil column leachate were significant influenced by landfill leachate (p<0.05). Therefore, the ratio of the component scores of the soil under the landfill to that of natural soil could be used to evaluate the leakage status of landfill leachate. Furthermore, a hazard index (HI) and a hazard evaluation standard were established. A case study of Kaifeng landfill indicated a low hazard (level 5) by the use of HI. In summation, HI is presented as a tool to evaluate landfill pollution status and for the guidance of municipal solid waste management.

Experimental Study on the Emergency Disposal Agent for Methanol Leakage

According to the characteristics of methanol leakage hazard, a new kind of foam decontamination agent was prepared and tested. Experiments were conducted in a laboratory-scale apparatus, where the effect of composition and amount on the decontamination performance of the foam was studied in detail. Results showed that the decontaminating efficiency of the foam was above 92% with the volume of foam agent sprayed 3 times of the methanol leaked. Moreover, the thick foam layer could stably cover the liquid methanol for a long time, efficiently inhibiting the volatilization of methanol vapor. Such performance of the foam agent was much superior to that of the commonly used water mist and activated carbon powder. The results are expected to provide useful experimental data and theoretical basis for the practical emergence disposal of methanol leakage.

Risk Reduction by Automatic Seismic Shutoff

Seismic shutoff devices are expected to automatically stop the flow of hazardous gases and liquids through distribution systems that may be damaged by earthquakes. There is some uncertainty in the actuation of these devices; they may actuate when not needed and they may not actuate when needed. Therefore, these devices can only reduce, and not eliminate, the risk of hazardous leaks. It is shown in this paper that shutoff devices can be deployed to meet specific performance goals in seismic design. A cost-benefit analysis is conducted to show that devices are most effective in reducing the risk to weak systems in highly seismic areas. The uncertainty in actuation diminishes the effectiveness of these devices.

Gas leakage hazard zonation of Masjed-i-Soleiman area, Zagros, Iran, using GiT

The shallow Masjed-i-Soleiman (MIS) oil field is situated at the Dezful Embayment in the Zagros Fold and Thrust Belt in southwestern Iran. The shallow depth of this oil field and multiple fractures has resulted in many gas leakages causing a significant pollution in residential areas around the area. In order to define the extent of the gas leakage, data sets such as surface structures, underground contour map, detected gas leakages, lithology, digital elevation models and population density were compiled using of remote sensing techniques and field investigations. The data were then added as layers in a geographic information system, which were overlaid form comparisons and used to construct a gas leakage hazard zonation map. This study shows that the central part of the MIS area, around the See-Berenj, Naftoon and Darre-Khersun districts, is a high-risk area, because of the shallow depth of gas caps, localizing of popular habitation and the high density of fractures and gas leakages.

Lost But Not Forgotten: The Hidden Environmental Costs of Compensating Pipelines for Natural Gas Losses

Lost But Not Forgotten: The Hidden Environmental Costs of Compensating Pipelines for Natural Gas Losses

Seal evaluation and confinement screening criteria for beneficial carbon dioxide storage with enhanced coal bed methane recovery in the Pocahontas Basin, Virginia

The geological storage of carbon dioxide in Appalachian basin coal seams is one possible sink for sequestration of greenhouse gases, with the added benefit of enhanced-coal bed methane (ECBM) recovery. The Pocahontas Basin (part of the central Appalachian Basin) of southwestern Virginia is a major coal bed methane (CBM) province with production mostly from coal beds in the Lower Pennsylvanian Pocahontas and New River formations. As part of the Southeast Regional Carbon Sequestration Partnership's Phase II research program, a CO2-injection demonstration well was installed into Lower Pennsylvanian coal bed-methane producing strata in southwest Virginia. Samples of siliciclastic lithologies above coal beds in this Oakwood Field well, and from several other cores in the Nora Field were taken to establish a baseline of the basic confinement properties of overlying strata to test seal competency at local and regional scales. Strata above CBM-producing coal beds in the Pocahontas and New River formations consist of dark-gray shales; silty gray shales; heterolithic siltstones, sandstones, and shales; lithic sandstones, and quartzose sandstones. Standard measurements of porosity, permeability and petrography were used to evaluate potential leakage hazards and any possible secondary storage potential for typical lithologies. Both lithic- and quartz-rich sandstones exhibit only minor porosity, with generally low permeability (< 0.042 mD). Interconnected porosity and permeability are strongly impacted by diverse cementation types and compaction. Analyzed siliciclastic lithologies are considered tight, with limited primary matrix permeability risks for leakage, providing an ensemble of redundant CO2-ECBM traps. One of the most promising confining intervals above the major coal bed-methane producing interval is the Hensley Shale Member. Analyses of 1500 geophysical logs in southwest Virginia indicate that this unit is moderately thick (> 50 ft, 15 m), laterally continuous (> 3000 km2), and a homogenous shale, which coarsens upward into siltstone and sandstone, or is truncated by sandstone. Calculations from two mercury injection capillary porosimetry tests of the shale indicate that a displacement entry pressure of 207 psi (1427 kPa) would generate an estimated seal capacity of 1365 ft (416 m) of CO2 before buoyant leakage. Scanning electron microscopy indicates a microfabric of narrow pore throats between quartz grains floating in a clay matrix. Modeled median pore throat size between micro-fabric matrix grains for the shale is estimated at 0.26 μm. These characteristics indicate that the shale, where fractures and joints are limited, would be an adequate regional confining interval for deeper CO2 storage with ECBM.

Locating inspection facilities in traffic networks: an artificial intelligence approach

In order for traffic authorities to attempt to prevent drink driving, check truck weight limits, driver hours and service regulations, hazardous leaks from trucks, and vehicle equipment safety, we need to find answers to the following questions: (a) What should be the total number of inspection stations in the traffic network? and (b) Where should these facilities be located? This paper develops a model to determine the locations of uncapacitated inspection stations in a traffic network. We analyze two different model formulations: a single-objective optimization problem and a multi-objective optimization problem. The problems are solved by the Bee Colony Optimization (BCO) method. The BCO algorithm belongs to the class of stochastic swarm optimization methods, inspired by the foraging habits of bees in the natural environment. The BCO algorithm is able to obtain the optimal value of objective functions in all test problems. The CPU times required to find the best solutions by the BCO are found to be acceptable.

Corrosion under insulation

AbstractCorrosion under insulation (CUI) is a major problem for petroleum and chemical process industries. CUI can result in sudden and hazardous leaks (safety concern), and plant shutdowns with high losses of production‐volumes (economical concern). A few examples are described in this article to illustrate the problems with CUI. This article discusses the root causes of CUI and recommendations to prevent it. One of the major recommendations is the use of risk‐based inspections (RBI) and the details of this RBI method are described. CUI can be especially avoided through a good cooperation between operations, inspection, and maintenance departments. © 2008 American Institute of Chemical Engineers Process Saf Prog, 2009

In-house off-shoring of product development by MNCs

This paper deals with in-house off-shoring of product development activities, here defined as the cost and efficiency motivated shifting of product development projects within the network of multinational companies (MNC) to low and medium wage countries. The aim of the paper is to develop and test a succinct model which is based on transaction cost reasoning and which explains how and why different governance forms can be combined in order to reap efficiency gains in off-shoring. The results from a structural equations model suggest support for a configuration which positively associates in-house off-shoring with local outsourcing and negatively associates in-house off-shoring with local cooperation in product development. The results are moderated by size and age of the MNC subsidiary, suggesting that larger subsidiaries are more likely to become an offshore destination and to outsource part of their product development. I argue that this combination of governance forms increases scale, flexibility and speed to market while reducing costs and knowledge leakage hazards. The results imply that the internalization theory should be extended in order to take account of off-shoring and its distinctive characteristics.