Dry Pipe Research Articles

Improvement of the Prototype of the Compressed Air Foam System and its Testing

The prototype of the compressed air foam system was improved based on the evaluation of the numerical parameters obtained with the help of the developed mathematical model of the foam generation process and the pneumatic-hydraulic scheme. The prototype provides the possibility of foam generation both in autonomous mode, due to the installation of cylinders with compressed gas, and in stationary mode, due to the supply of compressed air from an external source. This allows the use of an improved model of the compressed air foam system both in stationary mode (dry pipes, gas stations, etc.) and for use on heavy and light fire trucks, which is important for large cities. Testing of the improved prototype of the system for extinguishing model fires was carried out. The system provides extinguishing of model fires of class 183 B and 144 B when using both a general-purpose foaming agent and a special film-forming foaming agent. When using a film-forming foaming agent, the extinguishing time was reduced by 1.75 times, the consumption of fire extinguishing solution by 1.47 times. But at the same time, it should be taken into account that the cost of the film-forming foaming agent Sofir (sofirafff 6 %) is more than 3.2 times the cost of the general-purpose foaming agent Sofir. The effectiveness of the improved model in extinguishing class A fires was also confirmed. The autonomous compressed air foam system ensures extinguishing of a class 4 A model fire in 90 seconds. Dry foam with a factor of 14 is noted to be more effective in extinguishing solid combustible substances.

Hydrothermal aging effect on crushing characteristics of intraply hybrid composite pipes

In this study, the crushing properties of hybrid glass, basalt, and carbon fiber-reinforced composite pipes under a hydrothermal aging environment were investigated. Hybrid and non-hybrid composite pipes manufactured by filament winding technique were immersed in distilled water and seawater at 30 °C for four months. The water sorption parameters of the samples were calculated theoretically and weighed experimentally. Dry and aged pipes were subjected to quasi-static axial compression to examine aging effects on the crushing properties. The experimental weighing results showed that all composites exhibited a Fickian-like water absorption line. The non-hybrid basalt pipes were the most water-absorbing among all groups. In addition, the results proved that the hybridization effect in pipes is highly effective on water absorption parameters. In line with the results of non-hybrid pipes, hybrid pipes containing basalt fiber absorbed more water than other hybrid ones. Additionally, pipes aged in different environments showed that composite pipes absorbed more distilled water compared to seawater. Also, it was found that hydrothermal aging having adverse effects on the crushing characteristics of the pipes led to significant decreases. This can be explained by the degradation of the fiber–matrix interphase due to aging. However, maximum specific energy absorptions were achieved from non-hybrid carbon pipes regardless of environmental conditions. Also, the hybridization enhanced the crushing properties of the non-hybrid pipes that have lower characteristics. Additionally, it can be said that hybrid samples providing better stability in crushing showed better mean crushing load values since they mostly had a progressive crushing mode. The maximum mean crushing loads were obtained from the unconditioned hybrid GC samples as 36.2 kN which was 9.5 % and 34 % higher than unconditioned hybrid CB and BG samples. In conclusion, the study proved that the samples with low crushing properties can be improved by hybridization even if they are subjected to harsh environmental conditions.

A Comparison of the Performance of Four Acoustic Modulation Techniques for Robot Communication in Pipes

Autonomous robotics is an emerging technology for the inspection of a vast network of underground pipes. Communication between autonomous robots is essential to optimise their efficiency and network coverage. However, sending a message acoustically is not a well-researched topic because most of the existing literature is devoted to the study of the acoustic properties of the pipe for the purpose of sensing rather than communication. In particular, the influence of multi-modal propagation and background noise on the quality of acoustic communication in pipes has not been well understood. This paper studies the performance of four standard acoustic communication techniques in a dry drainage pipe to fill this knowledge gap. The noise resistance, communication range and data rate of these techniques are estimated through numerical simulations and laboratory experiments. It has been found that the techniques based on shift keying requires at least 5--10 dB signal to noise ratio (SNR) to function properly while the chirp linear frequency modulation technique can operate reliably with SNR = 0 dB or event lower SNR. The results also suggest that the multi-modal propagation in the pipe has significant effects on the package error rate. The frequency dependent sound attenuation in the pipe also affects the communication range and data rate. In particular, for a 150 mm diameter dry pipe the maximum robot operation distance is likely to be limited to 50--100 m with the highest carrier frequency of around 10 kHz and data rates below 6300 bps. The results of this work pave the way to the development of acoustic communication modules to be deployed on tetheless robots designed to inspect a buried pipe network autonomously and collaboratively.

Features of realization of fire-fighting water supply of the facility on the example of national cultural-artistic and the museum complex "Mystetskyi Arsenal"

The results of the implementation of fire water supply requirements during the restoration and adaptation of the historical and architectural monument "Old Arsenal" in Kyiv are presented. Alternative measures of fire safety and compensation of deviations from the norms on fire protection and in particular fire water supply of the object, which is of cultural and artistic value and requires special approaches to engineering and organizational and organizational solutions are substantiated. analysis of volumetric and structural parameters of the building, which affect the engineering and organizational and organizational decisions while providing fire protection of the object. An alternative implementation of internal fire water supply for the first and basement floors of the facility is proposed, by placing external cabinets of dry pipe fire hydrant kits or external fire hydrants, which are functionally related to the internal fire water supply system. Based on the analysis of volumetric and structural parameters of the object and potential hazards that may arise, the principle of installation of external fire water supply and fire hydrants on its territory to ensure the possibility of quick connection of fire hoses and their laying through windows and pits to the premises Object. Based on the above analysis and justifications, conclusions were made on the need to amend the existing state building codes in terms of designing internal and external fire water supply.

Experimental Investigation on the Effects of Exhaust Emission Reduction in a Single Cylinder CI Engine Fuelled with Diesel and Diesel Plastic Pyrolysis Oil with Zeolite Nanomaterials

The steady-state activity of zeolite 4A and 5A has been investigated experimentally for nitrous oxide and other emission gases in highly oxidizing conditions, typical for lean-burn engine exhaust. Zeolite has been characterized by XRD and FTIR. The CAD model is designed which shows the layout and basic mounting points of the catalytic converter on the Kirloskar TVI engine. Zeolite 4A and 5A substrate has been made using simple molding techniques, further heating it in an electric heater at 650°C for 6 hours. Several fuels such as plastic pyrolysis oil and diesel oil have been used to investigate the effect of NO on zeolite 4A and 5A substrate. The NO conversion has been found to be decreased by 40% using plastic pyrolysis oil. The zeolite powder has been added with 8% of bentonite clay and 5% of carboxymethyl cellulose powder, and 34% distilled water was stirred constantly to form like molding sand. The applied torque was monitored during stirring, signifying even mixing. The mixture has been kept in the prearranged mold design, and uniform pressure has been applied to guarantee no air holes in the shape. The hole pattern has been made using SOLIDWORKS and has been printed to get reliable openings (10 mm) with the assistance of wooden bars; the prearranged mold has been dried for 92 h in the immediate daylight; thereafter, dry pipes have been taken out from the mold. The subsequent form has been kept in the furnace at first at 150°C. Carboxymethyl cellulose is utilized as a fastener which assists with shaping the mold since it has great binding properties. Significant NOx reduction of 45~50% using zeolite 5A and 27~30% using zeolite 4A mold structure with diesel fuel was observed. Reduction of 35~40% using zeolite 5A and 13~16% using zeolite 4A mold structure with PPO + diesel fuel was observed.

Study on Management Practices and Constraints of Black Head Somali Sheep Reared in Awbarre District of Fafen Zone, Somali Region, Ethiopia

The study was conducted to assess management practices and constraints of Black head Somali sheep in Awbarre district of Fafen zone, Somali regional state, Ethiopia. A total of 120 households were purposively selected for this study using purposive sampling technique. The data were collected through the questionnaire, key informants interview, focus group discussions & field observations. The primary purpose of keeping sheep was for income generation followed by saving, meat production, milk, social and cultural functions. The main feeds for sheep during wet season were communal & private natural pastures. In dry season, communal natural pasture, crop residues & private natural pasture were used. The major source of water during wet season was dam/pond, whereas in the dry season spring & pipe water were used. The majority of the respondents (85.8%) used houses enclosed with thorn woody trees and houses enclosed with stone/brick fence were also reported. Majority of the respondents used controlled mating system and sheep are bred to lamb when forage is plentiful because they are less drought tolerant than goats and to avoid unwanted lambing in dry season. Majority (90%) of respondents own their breeding ram and those who have no breeding males used their neighbors’ rams and borrow from others. The breeding rams were born in the flock implying that animals within the flock are very closely related which leads to inbreeding. The most important health problems affecting sheep were circling disease, sheep pox, tick lameness (tick paralysis), Peste des Petits Ruminants (PPR), bloating, and Foot & mouth disease (FMD). The major constraints hindering sheep production in the study area were shortage of veterinary service, feed shortage, scarcity of water, predators, diseases, and marketing. Therefore, to improve and increase the productivity of sheep production in the study area, better management practices and establishing of veterinary service centers are necessary.

Unusual hydrogen explosions due to unanticipated metal‐water reactions

AbstractInadvertent generation of hydrogen from ambient temperature metal‐water chemical and electrochemical reactions have been responsible for a surprising number of hydrogen explosions. This paper describes three sets of incidents involving different metals in applications that are normally considered free of explosion hazards. The first set of incidents involves wet alkaline incinerator ash with an aluminum content of at least 2%. The second set of incidents involves copper conductor electrochemical reactions in subsea electrical cable. The third set involves electrochemical corrosion reactions in galvanized dry sprinkler pipe. In all three applications, test data are discussed to elucidate the specific reactions and potential preventive and mitigation measures.

The influence of the thickness of an aluminium radiant sheet on the performance of the lightweight floor heating

The aim of this work is to determine the optimal thickness of aluminium radiant sheet in the lightweight floor heating, i.e. the smallest thickness of the aluminium, ensuring high efficiency and thermal comfort. The optimal operational and construction parameters are determined regards to the aluminium thickness. Finding the optimal aluminium thickness is important for economic and ecological reasons: less aluminium thickness, less aluminium consumption and less cost of construction. Numerical calculations were performed with ANSYS Steady-State Thermal Solver (Workbench 19.2) for floor heating with a dry screed, wood-like board and pipes embedded in the layer of tile adhesive. The influence of aluminium thickness changes in the range of 0.1–0.5 mm was analysed for variable water temperature, pipe spacing and constructions. The optimal aluminium radiant sheet thickness is 0.3 mm, 0.1 mm is not recommended. The optimal water temperature is 25–35 °C, 45 °C is not recommended. Constructions with a dry screed 25 mm thick should not be used. Constructions with pipes in tile adhesive should be used at a water temperature of 25–30 °C and an aluminium thickness of 0.3–0.5 mm. Constructions with wood-like board should be used at a water temperature of 25–35 °C and an aluminium of 0.3–0.4 mm. Results enable a conscious choice of such constructions and operational parameters of lightweight floor heating that ensure high efficiency, thermal comfort and low investment costs. The work includes the original specification of the lightweight floor heating efficiency depending on the radiant sheet thickness and specifies recommended radiant sheet thicknesses.

Hypothesis of the nature of cross-sectional shape distortion of the cold-pilgering mill die groove during dry pipe rolling

The paper provides results on the further development of a method for calculating heat emissions during plastic strain in its instantaneous deformation zone in the course of cold pilgering of pipes, such as the ones that affect the working tool deflection in coldpilgering mills and mechanical properties of wrought pipe metal. It was determined that a decrease in the cross-sectional depth of the coldpilgering mill die groove due to thermal distortions (thermal effect) caused by plastic strain of a pipe in the instantaneous deformation zone is in direct proportion to the distance of the die groove longitudinal section considered to the roll barrel edge. It was found that sections located closer to the roll barrel receive thermal distortion of a lesser degree. A method is proposed for thermal distortion compensation in roll-pass design calculation. Experiments on applying marks on the roll barrel surface near the groove taper showed that the maximum galling of marks takes place directly near tapers. This indicates the local nature of thermal expansion. Dependencies are presented to determine the value of tool geometry variation depending on the heating temperature. The presented dependencies were tested experimentally and were introduced as a basis for developing the method of calculating the transversal die groove parameters for the cold-pilgering mill taking into account local thermal expansion in the instantaneous deformation zone. The inferred law allows taking into account the influence of cold pilgering peculiarities on the variation of the die groove cross-section geometry in the cold-pilgering mill, pipe dimensions and performance parameters.

The Effect of Urease Inhibitors Coated Urea on the Growth, Physiological Activities and Yield of Maize (Zea mays L.) in Inceptisol Jogonalan, Klaten

An approach to minimize the loss of nitrogen (N) evaporating from urea is by inhibiting urease activity by urea coating with N- (n-butyl) thiophosphoric triamide (NBPT) and N- (n-propyl) thiophosphoric triamide (NPPT). The effect of urease inhibitor to minimize N loss has not been done in inceptisol soil. The purpose of this study was to study the effect of urease inhibitor coated urea on growth, physiological activity and yield of maize in Inceptisol Jogonalan, Klaten, Indonesia. The treatment was laid out in a Randomized Complete Block Design with 4 replications namely N0 (without fertilizer), N1 (urea + NBPT 348 kg ha-1) and N2 (urea + NBPT 278 kg ha-1). All treated plants was fertilized once in one growing season 3 weeks after planting (WAP). Observations were done on several variables: soil physicochemical characteristics, plant physiological activity as well as growth and yield of maize. Data were analyzed using Analysis of Variance (ANOVA), and then the mean comparisons were done by using Least Significance Difference (LSD) test at 5%. The results showed that fertilization affected all observed variables. The effect of urea-coated urea inhibitor urease (NBPT+NPPT) compared with N0 (control) showed very optimum result, especially in N2 treatment. The urea coated with NBPT + NPPT (urease inhibitors) was more effective at lower dose of 278 kg ha-1 and tended to provide better results indicated by the growth and yield of maize in Inceptisol, Jogonalan, Klaten. The better growth as well as the higher yield of maize that was indicated by seed weight of 11,45 tons ha-1 and 100-seed weight of 37.75 g were obtained from N2 treatment as compared to other treatments. The hybrid maize (P35) has an optimum yield potential of 12.1 tons of dry pipes per hectare.

Experimental and numerical study of sprinkler fire protection systems: Effect of initial pressure on system performance

The present study concerns the reliability and efficient design of full-scale automatic sprinkler systems for the fire protection of industrial facilities and process plants. In particular, sprinkler systems filled with pressurized air at idle state (dry pipe) were considered. In this prospect, Computational Fluid Dynamics (CFD) simulations were carried out in the framework of the OpenFOAM package to study the flow in the piping subsequently to the activation of one sprinkler head. A VOF (Volume of Fluids) approach was used to compute the air/water interface accounting for the compressibility of air (perfect gas), while turbulence was considered using the RANS-based k-e realizable model. In addition, specific routines were developed for the pump and sprinkler modelling, taking into account the phenomenon of choked flow when sonic velocity is reached at the outlet. The numerical results were first compared to measurements on a test bench of Gridded typology (scale 1 in volume) for the purpose of validation. Then, the influence of various parameters (i.e. initial pressure in the system, dimension of the outlet orifice) on the flow dynamics were assessed for sprinkler systems of Gridded and Tree typologies. In particular, the performance was evaluated in terms of time constant of the systems, i.e. the time necessary to reach steady-state water flow at the opened sprinkler head required to control a specific fire hazard.

Evaluation of US Federal Guidelines (Primary Response Incident Scene Management [PRISM]) for Mass Decontamination of Casualties During the Initial Operational Response to a Chemical Incident

The aim of this study was to evaluate the clinical and operational effectiveness of US federal government guidance (Primary Response Incident Scene Management [PRISM]) for the initial response phase to chemical incidents. The study was performed as a large-scale exercise (Operation DOWNPOUR). Volunteers were dosed with a chemical warfare agent simulant to quantify the efficacy of different iterations of dry, ladder pipe system, or technical decontamination. The most effective process was a triple combination of dry, ladder pipe system, and technical decontamination, which attained an average decontamination efficiency of approximately 100% on exposed hair and skin sites. Both wet decontamination processes (ladder pipe system and technical decontamination, alone or in combination with dry decontamination) were also effective (decontamination efficiency >96%). In compliant individuals, dry decontamination was effective (decontamination efficiency approximately 99%), but noncompliance (tentatively attributed to suboptimal communication) resulted in significantly reduced efficacy (decontamination efficiency approximately 70%). At-risk volunteers (because of chronic illness, disability, or language barrier) were 3 to 8 times slower than ambulatory casualties in undergoing dry and ladder pipe system decontamination, a consequence of which may be a reduction in the overall rate at which casualties can be processed. The PRISM incident response protocols are fit for purpose for ambulatory casualties. However, a more effective communication strategy is required for first responders (particularly when guiding dry decontamination). There is a clear need to develop more appropriate decontamination procedures for at-risk casualties.

Dry Pipes: Associations between Utility Performance and Intermittent Piped Water Supply in Low and Middle Income Countries

Intermittent piped water supply impacts at least one billion people around the globe. Given the environmental and public health implications of poor water supply, there is a strong practical need to understand how and why intermittent supply occurs, and what strategies may be used to move utilities towards the provision of continuous water supply. Leveraging data from the International Benchmarking Network for Water and Sanitation Utilities, we discover 42 variables that have statistically significant associations with intermittent water supply at the utility scale across 2115 utilities. We categorized these under the following themes: Physical infrastructure system scale, coverage, consumer type, public water points, financial, and non-revenue water and metering. This research identifies globally relevant factors with high potential for cross-context, scaled impact. In addition, using insights from the analysis, we provide empirically grounded recommendations and data needs for improved global indicators of utility performance related to intermittent supply.

Проблемы разработки методики испытаний неметалли- ческих труб и фитингов и гибких металлических труб на пожаростойкость

Advantages of use of nonmetallic pipes as pipeline systems for drencher and sprinkler wet and dry pipe automatic fire extinguishing installations (AUP) are considered. The analysis of advantage of use of nonmetallic pipes and flexible metal pipes in drencher and sprinkler wet and dry AUP is performed. Regulations for design of pipeline networks consisting of these pipes are provided. Distinctions in methods of fire testing of substances, materials and products for flammability, flame distribution, combustibility, fire resistance and fire endurance are shown. The domestic and foreign stands and methods connected with direct pipe testing for fire endurance are considered in detail. It is noted that the bench equipment, test methods and modes stated in domestic and foreign standards and patents for invention do not answer fully assigned purposes. The dependence of change of sprinkler angular attitude on its weight and console length is considered. It is shown that fire endurance as an integral characteristic allows carrying out an engineering choice of specific pipes and fittings for real fire-hazardous objects. There is reasoned the interconnection of test parameters and wet AUP functioning both in operating and standby conditions (wet or dry) with the pipe condition in the course of their operation (with or without water discharge). Nomenclature and the values of the set of parameters characterizing fire endurance are proved. As a set of parameters characterizing fire endurance, there are proposed the test duration before the depressu-rization of the pipe, temperature of tests, hydraulic or pneumatic pressure and water discharge through the pipe carried out automatically in fixed time after the beginning of the test. Test validation of the nature of the orientation angle change of the sprinkler axis (or a spray) must be given depending on its weight, console length and manner of pipe fastening (sliding or rigid). The criterion for the positive assessment of each test is lack of integrity loss of the test pipes and fittings, and also orientation stability of the sprinkler (or spray) in space (within the possible deflection angle). The special design of the test pipe is offered for the orientation check of sprinkler axis concerning the initial position. The stand is developed for the fire endurance definition of nonmetallic pipes (with and without fittings) and the sequence of performing operations is formulated. For control automation of depressurization there were used various technical means responding to pressure drop, to appearance of water streams or smell (at control by a dry pipe).

Chatter vibration phenomenon of pipeline inspection gauges (PIGs) in natural gas pipeline

Pipeline inspection gauges (PIGs) are needed for operations such as cleaning and internal inspection of the natural gas pipelines to facilitate improvement in efficiency and safety. There is chatter vibrations appeared in PIGs when they run in the dry pipe with the wear of rubber sealing disc. Dry friction-induced self-excited vibration between sealing disc and pipe is the source of chatter vibration on PIG. In this paper, an experimental setup for measuring chatter vibration response signal of a typical bi-directional PIG running in a real dry steel pipe was implemented. The reason that cause self-excited vibration which manifest as chatter vibration on PIG, was explained through the analysis of classic dry-friction model. A self-excited vibration model based on LuGre friction model was proposed for better understanding of the phenomenon of chatter vibration during the process that PIG running through the natural gas pipeline, and the model was solved by MATLAB/SIMULINK. Our results show that the PIG runs in dry pipe with chatter vibration at a certain period within micro-vibrations in the single ladder period. Dry friction-induced self-excited vibration between sealing disc and pipe is the source of chatter vibration on PIG, and lead to the wear of PIG's sealing disc in natural gas pipeline; the negative damping of system in dry friction contact is the reason that causes self-excited vibration; the simulation of the numerical model can validate the PIG's self-excited phenomenon well. These results provide a better understanding of the complex behavior of PIG motion within natural gas pipelines.

Experimental study of water hammer-induced forces and deformations in dry pipe fire protection systems

When designing a fire protection system, every effort should be taken to ensure its maximum operational safety. Therefore, correct identification of the dynamic load affecting the system during water hammer occurrence is essential to increase the operational reliability of such fire protection systems on their design stage. A test stand with a simple deluge system was designed for the experiments. The layout consisted of a distribution duct and one straight branch line (including three different diameter values) equipped with three fire nozzles. However, the main objective of this study is not to study the water hammer itself but, rather, to study the forces and displacements induced by the water hammer. The measurement results will be used to calibrate a mathematical model created using MATLAB software. The verified model will in turn enable numerical determination of the dynamic force values for larger systems. Furthermore, these force values will allow for pinpointing the critical sections, for which it is necessary to prevent displacements or transfer the acting forces to the building structure.

Numeric simulation of non-steady flow of liquid in dry pipe fire protection systems of tree type topology

The mathematical model of the dry pipe fire protection system having a tree type configuration is presented. It provides the quantitative description of the non-steady processes in it after sprinklers are opened: the gas discharge to ambience, filling up piping with liquid and the liquid discharge through sprinklers. The algorithm is developed for the dynamic formulation of system of equations at various stages of filling up piping with liquid. The effective procedure for the numerical solution of system of equations is presented as well as description of its application for calculating non-steady characteristics of liquid motion in a piping system. Calculated results are compared against experimental data for the trip, the transit, and the operating pressure time proving adequate accuracy of the developed model.

Determination of Clothing Evaporative Resistance on a Sweating Thermal Manikin in an Isothermal Condition: Heat Loss Method or Mass Loss Method?

This paper addresses selection between two calculation options, i.e heat loss option and mass loss option, for thermal manikin measurements on clothing evaporative resistance conducted in an isothermal condition (T(manikin) = T(a) = T(r)). Five vocational clothing ensembles with a thermal insulation range of 1.05-2.58 clo were selected and measured on a sweating thermal manikin 'Tore'. The reasons why the isothermal heat loss method generates a higher evaporative resistance than that of the mass loss method were thoroughly investigated. In addition, an indirect approach was applied to determine the amount of evaporative heat energy taken from the environment. It was found that clothing evaporative resistance values by the heat loss option were 11.2-37.1% greater than those based on the mass loss option. The percentage of evaporative heat loss taken from the environment (H(e,env)) for all test scenarios ranged from 10.9 to 23.8%. The real evaporative cooling efficiency ranged from 0.762 to 0.891, respectively. Furthermore, it is evident that the evaporative heat loss difference introduced by those two options was equal to the heat energy taken from the environment. In order to eliminate the combined effects of dry heat transfer, condensation, and heat pipe on clothing evaporative resistance, it is suggested that manikin measurements on the determination of clothing evaporative resistance should be performed in an isothermal condition. Moreover, the mass loss method should be applied to calculate clothing evaporative resistance. The isothermal heat loss method would appear to overestimate heat stress and thus should be corrected before use.

Design of Dry Pipe Sprinkler Systems to Meet the Water Delivery Time Restriction in Industrial Freezers

Dry-pipe sprinkler systems are commonly used when the ambient temperature of a protected space is below freezing temperature of water. Because the degree of fire spread prior to sprinkler actuation is greater than that of the wet system in comparable circumstances, a greater coverage area is often required in a drysystem than that of a wet system. In addition, the dry system also requires the water delivery time to the most remote sprinkler be within a certain time limit. Dry-pipe ceiling-sprinkler restriction imposed by NFPA 13 for the protection of Class 2 materials in rack-storage higher than 7.6-m under 12-m ceiling is a maximum 30-seconds water delivery time with a 4-heads-open assumption. An in-house computer program developed to estimate water delay times in dry-pipe systems has been extensively used at FM Global for the last 15 years to address the water delivery time requirement mentioned above for industrial freezers. This paper describes how the program was developed and how the 30-seconds water-delivery time requirement could be met by choosing proper operating conditions through numerous real design cases. The examples showed that by adjusting many operating control parameters, most of the system could meet the 30-seconds water delivery time restriction without making substantial alteration in system configurations. The case study also shows that the air trip time linearly increases with the system volumes as anticipated. The water transit time also increases with the system volume in general, however, the dependence was more complex, which indicates that the system configuration plays an important role in the transit time in dry-pipe systems. Overall, the case study shows that the program had enabled the system design to be much more flexible and cost effective.

The acoustic attenuation and hydraulic roughness in a large section sewer pipe with periodical obstacles

The acoustic attenuation, relative sound pressure levels and the equivalent Nikuradse wall roughness under variable flow conditions in a 600 mm concrete sewer pipe are experimentally investigated. The values of the acoustic attenuation are obtained in the case of airborne sound propagation in the dry pipe. A range of values of the equivalent wall roughness is artificially generated by deploying a periodical array of engineering bricks. A novel method of rapid evaluation of the acoustic attenuation is proposed. The method relies upon sound reflections from the adjacent manholes. The results demonstrate that the acoustic attenuation depends strongly on the value of the equivalent wall roughness. This work can pave the way to the efficient methodology for the in-situ, physical evaluation of the equivalent hydraulic roughness of new and existing sewer networks.