Trap Seal Research Articles

Artificial neural network modelling for predicting classical air pressure profile curves in building drainage systems

Water trap seal loss can lead to the ingress of foul odours from the sewer network carrying harmful pathogens which can affect the health of building occupants. This loss is due to excessive negative or positive pressures within the system as a consequence of rapidly changing flow due to the unsteady nature of air and water flow discharges from appliances. This pressure regime within the system is often represented by a pressure profile along the height of the main vertical stack in the Building Drainage System (BDS). Experimental data from peer-reviewed literature and data from a unique 34-storey drainage test rig have been used as pressure profile data (Test data) for an Artificial Neural Network (ANN) model. Discharge input height (storey number) and discharge flow rate are considered to be the two independent input parameters and the pressure along the vertical stack is considered to be the output. In this work, both a Feed Forward and Back Propagation (FFBP) ANN model and a Radial Basis Function (RBF) ANN model have been used to train the algorithm. The work has confirmed the applicability of the FFBP-ANN model for steady two-phase fluid flow phenomena in BDS and allows for the prediction of pressures in a system for which no pressure data exists, by the prediction of modelled weights, based only on its physical and flow characteristics. Practical Application: Of great concern to designers of building drainage systems (BDS) is the control of pressure fluctuations within the system to prevent water trap seal loss. Prediction of a pressure profile based on the characteristics of the building – e.g. height, location of water discharge, discharge flow rate and ventilation type, would therefore increase confidence in designs, particularly in tall buildings. The work presented here addresses, for the first time, the applications of two ANN models for predicting the pressure profile in the BDS vertical stack of multi-storey buildings.

Research on the relationship between architectural features in northeast China and vertical aerosol transmission of COVID-19.

During the COVID-19 pandemic, many buildings in northeast China have had clusters of infected cases in the vertical layout. There is speculation that vertical aerosol transmission occurs. The houses in northeast China are airtight, and range hoods may be used for a long period of time when cooking. The pathway and factors influencing vertical aerosol transmission are worth studying. To elucidate a viral aerosol transmission pathway, we selected a multistory apartment and a high-rise building in Changchun city, Jilin province, China, to conduct an in-depth investigation and on-site simulation experiments. According to epidemiological investigation information on infected cases, building structures, drainage, ventilation, etc., we used fluorescent microspheres to simulate the behaviors of infected people, such as breathing and flushing the toilet after defecation, to discharge simulated viruses and track and monitor them. The field simulation experiment confirmed the transmission of fluorescent microsphere aerosols to other rooms in two types of buildings using a vertical aerosol transmission pathway of toilet flush-sewage pipe-floor drain without a water seal. Our study showed that, in the absence of a U-shaped trap or floor drain water seal whether in a multistory apartment or high-rise residential building, there is a transmission pathway of "excretion of virus through feces-toilet flushing-sewage pipe-floor drain without water seal," which will cause the vertical transmission of viral aerosol across floors during the COVID-19 pandemic. Moreover, the negative pressure generated by turning on the range hood when closing doors and windows increase aerosol transmission. Based on this negative pressure, prevention and control measures for residential buildings in northeast China during the COVID-19 pandemic were proposed.

A Photogrammetric Technique for Developing Boundary Equations for Flexible Sheath Waterless Trap Seals as Used in Building Drainage Systems

The water trap seal is still the main method of protecting building inhabitants from the ingress of foul contaminated air and noxious gases from the sewer. This seal can become compromised when water is lost in the trap by processes including evaporation and siphonage from excessive system suction pressures. A recent innovation is the waterless trap seal, which uses flexible sheaths, typically made from silicone rubber to form the seal. The sheath opens in response to a sub-atmospheric air pressure and will shut tightly under a supra-atmospheric pressure in order to form a seal. Full system numerical modelling of building drainage systems has offered insight into system responses to pressure transients and has opened up the evaluation of building wastewater systems to predictive modelling which has assisted in producing improvements to public health. A requirement of any predictive model is a mathematical representation of the physical characteristics of the system. This research develops a technique for developing boundary equations so that predictive modelling is possible. We combine photographic and pressure data analysed by Fourier analysis to develop the model. The technique is applicable to any device were the fluid structure interaction plays a significant role in its operation.

Building Drainage System Design for Tall Buildings: Current Limitations and Public Health Implications

National design guides provide essential guidance for the design of building drainage systems, which primarily ensure the basic objectives of preventing odor ingress and cross-transmission of disease through water-trap seal retention. Current building drainage system design guides only extend to buildings of 30 floors, while modern tall buildings frequently extend to over 100 floors, exceeding the predictive capability of current design guides in terms of operating system conditions. However, the same design guides are being used for tall buildings as would be used for low-rise buildings. A complicating factor is the historic roots of current design guides and standards (including the interpretation of the governing fluid mechanics principles and margins of safety), causing many design differences to exist for the same conditions internationally, such as minimum trap seal retention requirements, stack-to-vent cross-vent spacing, and even stack diameter. The design guides also differ in the size and scale of the systems they cover, and most make no allowance for the specific building drainage system requirements of tall buildings. This paper assesses the limitations of applying current building drainage system design guides when applied to the case of tall buildings. Primarily, the assessments used in this research are based on codes from Europe, the USA and Australia/New Zealand as representative of the most common approaches and from which many other codes and standards are derived. The numerical simulation model, AIRNET, was used as the analysis tool. Our findings confirm that current design guides, which have been out of date for a number of decades, are now in urgent need of updating as code-compliant systems have been shown to be susceptible to water-trap seal depletion, a risk to cross-transmission of disease, which is a major public health concern, particularly in view of the current COVID-19 pandemic.

Enhancing trap and fault seal analyses by integrating observations from HR3D seismic data with well logs and conventional 3D seismic data, Texas inner shelf

Abstract An understanding of trap and fault seal quality is critical for assessing hydrocarbon prospectivity. To achieve this, modern analytical techniques leverage well data and conventional industry-standard 3D seismic data to evaluate the trap, and any faults displacing the reservoir and top seal intervals. Above all, geological interpretation provides the framework of trap and fault seal analyses, but can be hindered by the data resolution, quality and acquisition style of the conventional seismic data. Furthermore, limiting the analysis to only the petroleum system at depth may lead to erroneous perceptions because interpreting overburden features, such as shallow faults or gas chimneys, can provide valuable observations with respect to container performance, and can to help validate trap and fault seal predictions. A supplement to conventional 3D data are high-resolution 3D seismic (HR3D) data, which provide detailed images of the overburden geology. This study utilizes an HR3D seismic volume in the San Luis Pass area of the Texas inner shelf, where shallow fault tips and a sizeable gas chimney are interpreted over an unsuccessful hydrocarbon prospect. Static post-drill fault seal and trap analyses suggest that the primary fault displacing the structural closure could have withheld columns of gas c. 100 m high, but disagree with our HR3D seismic interpretations and dry-well analyses. From our results, we hypothesize that tertiary gas migration through fault conduits reduced the hydrocarbon column in the prospective Early Miocene reservoir, and may have resulted from continued movement along the intersecting faults. Overall, this study reinforces the importance of understanding the overburden geology and geohistory of faulted prospects, and demonstrates the utility of pre-drill HR3D acquisition when conducting trap and fault seal analyses.

トラップ封水の蒸発現象に関する研究 第２報 実物トラップ実験および排水管内温湿度・風速計測

トラップ封水の蒸発現象に関する研究 第２報 実物トラップ実験および排水管内温湿度・風速計測

Experimental study on air pressure variation in a horizontal pipe of single-stack drainage system.

The water trap seal under the sanitary appliances is the primary defense against the ingress of foul gases and odors. However, research on air pressure variation in a horizontal pipe of a single-stack drainage system is very limited. Thus a physical model study was conducted to investigate the air pressure variation in a horizontal pipe. Four parameters were studied that affect the pressure variation; that is, water flow rate, inlet height, ventilation condition and outlet condition. When the top of the vertical drainage stack and the outlet were fully open to the atmosphere, the flow in the horizontal pipe changed from free surface flow to slug flow at certain times. The mean values and magnitudes of pressure fluctuation at measuring points on the horizontal pipe increased with Qw but decreased along the horizontal pipe. The inlet height had relatively small influence on the pressure variation. Three ventilation conditions; that is, top fully open, half open and sealed, were tested, and a choking flow was formed in the vertical drainage stack and the pressure in the horizontal pipe decreased under the top sealed condition. Three outlet conditions; that is, outlet fully open, half submerged and fully submerged, were tested. The pressure in the horizontal pipe increased significantly under the outlet fully-submerged condition, which should be avoided in the actual operation by careful designing.

トラップ封水損失に対する管内圧力の評価法の検討 : 第1報-管内圧力波形が封水に及ぼす影響の解析

トラップ封水損失に対する管内圧力の評価法の検討 : 第1報-管内圧力波形が封水に及ぼす影響の解析

A-39 トラップ性能に及ぼす環境に関する研究 (その2) : 室内圧力がトラップ封水に及ぼす影響に関する測定

A-39 トラップ性能に及ぼす環境に関する研究 (その2) : 室内圧力がトラップ封水に及ぼす影響に関する測定

A-30 室内負圧に関する調査研究 : その1) 便器トラップの封水性能に影響を与える要因の検証

A-30 室内負圧に関する調査研究 : その1) 便器トラップの封水性能に影響を与える要因の検証

G-23 トラップの性能試験法に関する研究 : (その1)正圧時の封水損失特性

G-23 トラップの性能試験法に関する研究 : (その1)正圧時の封水損失特性

3D Geological Model of Potential CO2 Storage: Abandoned Oil and Gas Field LBr-1in the Vienna Basin

Successful CO2 storage in abandoned oil and gas fields, building the underground gas storages, and enhanced oil and gas recovery require a functional 3D static geological model of the storage complex with the real geometry and conditions. Abandoned oil and gas field Lanzhot-Brodske North (LBr1) on the territory of the Czech Republic was selected for the preparation of a pilot research project of the geological CO2 storage. It is situated in the Northern part of the Vienna Basin, close to the Czech-Slovak border. The 3D-model includes a separate northern part of the LBr1 field. The 3D model is designed to serve as an input for the dynamic model and makes it possible to experiment and test simulations of the CO2 storage in a more-or-less real geological environment. The model documents areal and vertical extent of the storage complex, geological structure formed by the Lab reservoir horizon, trap seal built by the overlying clays, overlying and adjacent strata, aquifers, faults, natural and artificial migration paths. Further information provided by the model consists of the reservoir volume, pore space, reservoir properties, fluid distribution, and saturation by the pore fluids. A simplified 3D-model of the reservoir overburden offers a basis for risk analysis of potential fluid migration into shallower aquifers.

Modelling water trap seal boundary conditions in building drainage systems: Computational fluid dynamics analysis of unsteady friction to improve accuracy

The safe removal of disease-carrying human waste is the objective of all sanitation systems and the limiting of air pressure transients within the system remains a significant part of current codes and regulations. The water trap seal offers fundamental protection and is the system’s sole barrier between the public sewer network and habitable space inside a building. Modelling water trap seal responses to air pressure fluctuations offers an opportunity to analyse whole system performance, but the quality of the data depends on the accuracy of the modelling technique and that of the defining inputs. AIRNET, a 1D Method of Characteristics based model, enables rapid whole system testing; however, the present boundary condition for the water trap seal within the model is based solely on steady state conditions, ignoring system dynamics. Computational fluid dynamics offers an opportunity to numerically evaluate the flow patterns within the trap seal in response to applied air pressure transients. This research confirms the importance of the rate of rise, and hence frequency of air pressure transients incident on water trap seals and relates this to potential vulnerabilities of different device geometries, particularly the ratio between inner and outer wall length. The research led to the development of a dynamic velocity decrement model encapsulating unsteady friction and separation losses linked to device geometry for the first time. The development of a frequency-dependent internal energy term Δ v, suitable for inclusion in AIRNET provides the capability to predict more realistic water trap response to air pressure transients over a range of air pressure transient frequencies likely to cause problems: 1 Hz to 8 Hz.Practical application: Whole system modelling can greatly improve the ability of design engineers to fully simulate the operation of a building drainage system in a realistic way. The work described in this paper improves the accuracy of whole system models by evaluating water dynamic responses to air pressure transients using a range of techniques including computational fluid dynamics and more traditional 1D finite difference method of characteristics models. The work also paves the way for more robust evaluation of building drainage products through in-depth investigation of the fluid mechanics associated with their operation.

排水トラップ内誘導サイホン作用のCFD解析 第１報 トラップ封水変動の運動方程式とCFD解析法

排水トラップ内誘導サイホン作用のCFD解析 第１報 トラップ封水変動の運動方程式とCFD解析法

English

Knowledge of formation pore pressure ahead of the drill bit is not only critical for safe and cost-effective drilling of wells but also essential in studying the hydrocarbon trap seal and analyzing the trap configurations. A predrill estimate of the formation pore pressure can be obtained from seismic velocities and employing a velocity-to-effective stress transform. However, limitations abound in the use of seismic velocities for accurate pore pressure prediction. These limitations are traceable to some main factors such as the correctness of the seismic velocities themselves and the accuracy of the local parameters of the pore pressure prediction method used. Knowledge of the sources of overpressure in the formation is also an essential factor. This paper discusses these factors and attempts to put them into context for accurate pore pressure prediction using seismically-derived velocities.   Key words: Pore pressure prediction, overpressure, geopressure, seismic velocities, tomographic inversion, seismic inversion.

Numerical Simulation and Experimental Validation of Three-Dimensional Unsteady Multi-Phase Flow in Flushing Process of Toilets

In order to predict the flush performances of digital toilet products before mass production, a numerical simulation for a three-dimensional unsteady multi-phase flow in the flushing process of a wash-down toilet is carried out by using FLUENT software. The finite volume method (FVM) is used to discrete the three governing equations in space and time. The discrete equations are solved by using the first-order upwind discretization scheme and the PISO pressure-velocity coupling scheme. The realizable turbulence model is chosen as the viscous model to treat the fluid flow with large bending curvature wall. The volume of fluid (VOF) model is applied to solve the transient free-surface problem. First, a two-phase flow was simulated on the assumption that there is not sewage but water in the trap seal. Then, by simplifying the mixture of sewage and water in the trap seal as the third phase with high viscosity, a three-phase flow was simulated. Moreover, in order to validate the simulated results, a flushing testing was conducted to test the flush range, and a target type flow meter was designed, calibrated and applied to test the flush velocity. The comparisons show a good agreement between the numerical and experimental results. Based on the verified simulation results, the flush performances of the digital wash-down toilet, such as flush range, flush velocity and sewage replacement ability, can be predicted and evaluated.

Automatic detection of depleted fixture trap seals using the reflected wave technique

The loss of fixture trap seals presents a potential cross-contamination route for sewer-borne pathogens. The defective trap identification method was developed to assess the status of trap seals using a non-destructive ‘sonar-like’ test based on the reflected wave technique. System diagnosis, proven over several years of laboratory and sited-based validation, primarily depended on manual interpretation of system pressure responses to identify the trap location from the reflected wave return time. This paper advances the technique by introducing the developed ‘TRACER’ program which includes a time series change detection algorithm allowing automatic system diagnosis. Outputs were validated against simulations using the AIRNET numerical model which, together with the ‘PROBE’ Method, was used to determine trap pipe periods, and therefore the location of defective trap seals, with improved accuracy over those calculated theoretically. This technique thus provides a reliable and automated approach to monitoring the protective seal between habitable space and the sewer network. Practical application: Once installed, the building drainage system is often afforded little consideration in terms of regular maintenance, due partly to the problem of the ‘out of sight, out of mind’ mentality which is so often associated with this fundamental system, but also due to the practicalities of executing such an onerous task. Armed with a greater appreciation of the health risks associated with fixture trap seal loss, due to understanding its role in the transmission of the severe acute respiratory syndrome virus in 2003, building owners, operators and regulators must take action to safeguard the integrity of this important protective seal.

An assessment of, and response to, potential cross-contamination routes due to defective appliance water trap seals in building drainage systems

The outbreak of severe acute respiratory syndrome (SARS), centred on Southeast Asia in 2002 and 2003, sparked fears of an uncontrollable pandemic. The outbreak at one housing complex in Hong Kong resulted in a disproportionately large number of cases with 321 people contracting the virus, resulting in 42 fatalities. This outbreak led to an investigation by World Health Organisation, which firmly laid the blame for the spread of the virus in the housing complex on defects in the building drainage and vent system. The mode of viral transmission was identified as due to airborne aerosolised particles from virus-laden excreta emanating from the drainage system. The aerosolised particles were allowed to enter the habitable space through empty water trap seals which are the main protection against such ingress in a building drainage and vent system. This research reports on the defective trap identification system developed to provide a means of testing the seal afforded by the water trap seal inbuildings. This innovative sonar-like technology incorporates a means of identifying compromised water trap seals anywhere in a building in a repeatable, non-destructive manner. While the technology has been effectively validated by a combination of laboratory investigation, site testing and numerical simulation, the rationale for the need to monitor water trap seals is less obvious to professionals operating in this field. This article addresses this issue and presents such a rationale, identifying some of the harmful pathogens which could lead to cross-contamination from person to person via the building drainage system. Practical applications: The research carried out in this area has highlighted the lack of any real monitoring of water trap seal status in buildings and has put the issue firmly on the agenda for consideration by building owners, operators and regulators, for whom the building drainage and vent system has long been categorised as ‘fit and forget’. The inspiration for this study was the response to the SARS outbreak which began in 2002. The case to monitor this important seal is clearly made and whilst the predicted pandemic of the SARS virus failed to materialise on an extended time frame and the outbreak has largely been consigned to history, it should serve as a constant reminder to professionals in the industry that we ‘fit and forget’ at our peril.

A-30 トラップ性能に及ぼす環境に関する研究 : 室内圧力がトラップ封水に及ぼす影響に関する測定

A-30 トラップ性能に及ぼす環境に関する研究 : 室内圧力がトラップ封水に及ぼす影響に関する測定

Derivation of an empirical frequency-dependent friction factor for transient response analysis of water trap seals in building drainage systems

Flows in building drainage systems (BDS) are inherently unsteady. The changing nature of these flows produce pressure transients that can be harmful to water trap seals, the last line of defence against sewer gas ingress into habitable spaces. Air pressure transients propagate throughout BDS until they are diminished by either a relief valve, an open termination or, under certain circumstances, produce their own ‘relief valve’ through a compromised water trap seal. The spread of the SARS virus through empty water traps in Hong Kong in 2003 highlighted the worst possible consequences of water trap seal compromise. These air pressure transients can be simulated and their effects predicted. Only one numerical model exists for modelling airflow and the associated air pressure regime in BDS—the method of characteristics-based AIRNET. The current water trap boundary condition within the AIRNET model consists of a steady laminar frictional flow relationship, which does not replicate the unsteady pressure regime in the building drainage system. An improvement on this frictional representation is due to Carsten—Zilke, a methodology that allows a moving frictional term for water to trap surface interaction. This research proposes an alternative, empirically derived friction factor, and represents a significant simplification of the calculation process, leading to a robust, dynamic prediction methodology for water trap seal response to applied air pressure waves. Practical application: The development of new empirically derived frictional expressions to predict the effects of air pressure transients on appliance trap seals within a method of characteristics model provides far superior prediction results to those currently available. These new expressions enhance the modelling capabilities of AIRNET and prove that high frequency air pressure waves do not contribute to water trap seal depletion. The non-destructive nature of short duration or high frequency air pressure wave oscillations has contributed to the development of a non-invasive methodology for detecting water trap seal defects in building drainage systems, and this research serves to prove conclusively that using low amplitude, short duration pulses or sinusoidal pressure waves with a frequency above 3 Hz is non-destructive to traditional water trap seals in building drainage systems.