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Author: Thomas D. Rockaway
Publisher: American Water Works Association
ISBN: 9781583215821
Category : Elastomers
Languages : en
Pages : 0
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Book Description
For years the use of rubber gaskets, valves, hydrants, and fitting have been successfully widely used. However, recently an increase of elastomer failures has been noted. While the degradation appears to be coincident with a disinfectant change from chlorine to chloramines, other factors including temperature and pH and are believed to play roles. This research initiative was intended to clarify the factors that contribute to elastomer degradation and provide a quantitative method for predicting the performance and life expectancy of in-service elastomer components.
Author: Thomas D. Rockaway
Publisher: American Water Works Association
ISBN: 9781583215821
Category : Elastomers
Languages : en
Pages : 0
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Book Description
For years the use of rubber gaskets, valves, hydrants, and fitting have been successfully widely used. However, recently an increase of elastomer failures has been noted. While the degradation appears to be coincident with a disinfectant change from chlorine to chloramines, other factors including temperature and pH and are believed to play roles. This research initiative was intended to clarify the factors that contribute to elastomer degradation and provide a quantitative method for predicting the performance and life expectancy of in-service elastomer components.
Author: Raja Mohan Nagisetty
Publisher:
ISBN:
Category : Drinking water
Languages : en
Pages : 238
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Book Description
Over the last decade, chloramines have preferentially been used in place of chlorine as disinfectant, as a result of increasing health concerns and USEPA regulations associated with disinfection by-products (DBPs). While the switch to chloramines generally has been beneficial, subsequent to this change, several utilities have reported problems with substantially higher rates of elastomeric compound failures in their water systems. To predict the long-term performance of elastomers within the water systems, accelerated degradation experiments were conducted at the combinations of three temperatures (23°C, 45°C and 70°C) and three chloramine concentrations (1-, 30-, and 60 mg/L concentrations) for natural rubber, neoprene rubber, ethylene propylene diene monomer (peroxide-cured), ethylene propylene diene monomer (sulfur-cured), styrene butadiene rubber and nitrile rubber. Elastomer degradation was characterized by mass change, volume change, breaking stress, breaking strain and hardness. Using a time-temperature superposition (TTS) principle the accelerated test results were 'doubly-shifted' (temperature and chloramine concentration) to service conditions to generate long-term performance curves. As TTS technique was not suitable for mass change data, aqueous chloramine diffusion into styrene butadiene rubber and natural rubber was analyzed using Fick's second law of diffusion to develop long-term mass intake prediction curves. Diffusion coefficients were calculated for 1 mg/L chloramine concentration at three temperatures (23, 45 and 70°C) and also for 23°C, at three chloramine concentrations (1, 30 and 60 mg/L). For 1 mg/L chloramine concentration, activation energy for diffusion of SBR and natural rubber were computed to be 51.13 kJ/mole and 77.29 kJ/mole, respectively. Also, concentration profiles were developed to understand the extent of penetration along the elastomer thickness over time and temperature. To investigate the water quality concerns as a result of accelerated elastomeric compounds degradation, accelerated degradation tests were conducted in aqueous chloramine solutions and then the solutions were analyzed for organic compounds using SPME-GC/MS. The water quality concerns that could arise because of these elastomeric compounds degradation were discussed with relevant literature review in this study. Considering the reports of elastomeric compounds failure in chloramines disinfectant water distribution systems, this study would provide better tools for water industry in managing the risks associated with elastomer failure.
Author: Yakir J. Hasit
Publisher: American Water Works Association
ISBN: 1583215131
Category : Drinking water
Languages : en
Pages : 116
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Book Description
Many water utilities deal with water quality problems in the distribution system due to low water usage. This study uncovers the many problems of low usage and reports on the variety of mitigation practices used by North American utilities. An included CD-ROM provides decision support software to help utilities systematically weigh the costs and benefits of a variety of best management practices (BMPs) for mitigating the water quality issues caused by low usage and thus cutting down on customer complaints and higher distribution costs.
Author:
Publisher:
ISBN:
Category : Building
Languages : en
Pages : 554
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Book Description
Author: Randolph Norman Schoenbaechler
Publisher:
ISBN:
Category : Rubber
Languages : en
Pages : 72
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Book Description
The use of monochloramines in the potable water supply industry has been selected as the disinfectant method of choice due to a longer term of effectiveness and less toxic by-products than the previous choice of chlorine. In spite of the benefits exhibited by the use of monochloramines much greater rates of elastomer degradation have been noted in the water industry. The modes of attack by monochloramines on the rubber parts are still poorly understood. A common ingredient in nearly all elastomer formulations is carbon black. In addition to its role as a filler material, carbon black is also known to add strength and durability to the elastomer. Degradation of average particle size showing that carbon black particles dissolve into the invasive liquid medium can be observed using phase images produced by atomic force microscopy. The nanoscale size of the carbon black particles makes the use of the AFM an ideal investigative tool. Elastomeric properties of the rubber coupons exhibit similar trends to the degradation of the carbon black material in the polymer matrix. Diffusion coefficients approximated by use of a simplified form of Fick's second law also shows a similar trend. Use of monochloramines as a disinfectant by the water supply industry produce fewer toxic by-products and maintain a longer useful potable water life than chlorine; however, rapid degradation of rubber parts will continue unless more suitable formulations can be found.
Author:
Publisher:
ISBN:
Category : Plastics industry and trade
Languages : en
Pages : 918
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Book Description
Author:
Publisher: iSmithers Rapra Publishing
ISBN: 9781847350138
Category : Technology & Engineering
Languages : en
Pages : 216
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Book Description
Author: John Durkee
Publisher: Elsevier
ISBN: 0080464858
Category : Business & Economics
Languages : en
Pages : 481
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Book Description
More stringent quality standards and environmental/safety regulations as well as new process and chemical technology have changed industrial cleaning from a “wet and wipe application to a valued and demanding process operation. This book will help cleaning operatives, designers of equipment, metal finishers, industrial chemists and decontaminators understand the value and demands required within the industrial cleaning process and an environment of continuing change. * Covers all aspects of modern cleaning technologies, helping readers to understand basics of cleaning, equipment used, techniques and possible changes to come within the industry.* Includes environmental regulations and the basis for modern cleaning technologies, ensuring the reader is up to date on cleaning chemicals and their affects.* Covers testing for cleanliness, ensuring cleaning operatives, technicians and end users understand how to achieve the demands required within the industrial cleaning process and an environment of continuing change.
Author: Jahnavi Valleru
Publisher:
ISBN:
Category : Elastomers
Languages : en
Pages : 122
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Book Description
Elastomer degradation when exposed to chloraminated potable water is dependent on a number of poorly understood factors. Temperature and chloramine concentration are both believed to play roles, however, they have not been adequately defined. In order to estimate the material performance and predict the service life of elastomeric parts, knowledge of degradation modes, rate constants of the aging process and their activation energies is useful. EPDM elastomers are used in numerous applications which require resistance to ozone attack and weather due to their stable, saturated polymer backbone structure. Accelerated aging experiments were conducted on both EPDM - S and EPDM - P at three concentration levels and temperatures. Tensile properties are used to study the extent of degradation through a 30-day aging period which are used to estimate the crosslink densities of both the materials. A rate expression is developed based on the rate of change in cross link densities. The rate constants are estimated and they are used to estimate the activation energies and frequency factors using an Arrhenius relationship.
Author: National Institute of Standards and Technology (U.S.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 696
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Book Description
