Literatura académica sobre el tema "Winter hydraulic failure"

The article analyzes the causes of the destruction of road concrete in the winter. The basic theories of concrete failure during freezing are presented. Hypothesis of R. Collins according to which the destruction occurs as a result of the pressure of ice, which is formed when water freezes onto the pore walls. The hydraulic pressure hypothesis of T. Powers, according to which the main cause of concrete destruction during cyclic freezing and thawing, is the hydraulic pressure that creates water in the pores and capillaries of concrete under the action of ice. The hypothesis of thermal destruction of concrete due to the difference in the coefficients of linear thermal expansion of its components. In winter, sodium chloride (NaCl) solutions are most often used to combat ice on the surface of road surfaces. Therefore, an important consequence of this may be osmotic pressure. To calculate the osmotic pressure, the Vant-Hoff formula for true solutions was used. The maximum values of the osmotic pressure were determined at temperatures of 255...293 K. The critical concentrations of sodium chloride solutions at which concrete was destroyed were calculated. It was established that at the initial stage of freezing-thawing of concrete with the simultaneous action of an aqueous NaCl solution, the structure of concrete is densified and its strength is increased.

Abstract The paper deals with an impact of non–mechanical loads on the state of strength in massive concrete hydraulic structures. An example of hydroelectric plant subjected to the effect of water temperature annual fluctuation is considered. Numerical analysis of transient thermal–elasticity problem was performed. After determining the temperature distributions within the domain, the Duhamel-Neumann set of constitutive equations was employed to evaluate fields of mechanical quantities: displacement, strain and stress. The failure criterion proposed by Pietruszczak was adopted in assessing whether the load induces exceeding of strength of concrete within the structure volume. The primary finding is that the temperature effect can lead to damage of concrete in draft tubes and spirals, especially in winter months.

In July 1987, a section of the southwest wall of Sault Ste. Marie Lock failed during a locking operation when a portion of limestone facing, 60 m by 8 m, separated from the rubble backing wall. Engineering investigations resulted in the selection of the Recreational Lock Option, involving either downsizing the lock chamber within the existing lock or constructing a new lock as the most viable solutions. A Dry Dock Option, where the lock would be used to store craft during the winter months, was also considered. However, this option was abandoned during the course of testing. The engineering investigations also revealed that the emergency swing dam, constructed upstream of the existing lock to protect the system should the lock gates be damaged or carried away (as happened in 1909), was in poor condition and required rehabilitation in the order of over $0.5 million. A stop log emergency system was proposed as an alternative safety device designed to stop the flow of water through the canal in the event of gate failure. Physical hydraulic model studies were carried out to evaluate the feasibility of using an emergency stop log system. The tests showed that stop logs constructed with solid horizontal web plates top and bottom result in unacceptably high hydraulic downpull forces. Open truss stop logs can be deployed to stop the flow of water through the canal in the event of gate failure. The follower should also be constructed as an open truss such that the areas of steel exposed to the flow at the top and bottom of the follower are minimized. Hydraulic uplift forces that could prevent closure can be reduced by increasing the space between the stop log and the follower. Physical hydraulic model studies of the lock filling-emptying systems are described. The first and preferred option consists of downsizing the existing lock and retaining part of the existing wooden culverts and emptying system, if possible. A new filling port, filling valves, and supply culvert would be constructed upstream. In the event that the existing wooden culverts are found to be unserviceable, a second option was considered. This second option would be to fill in the wooden culverts and then construct a new filling port, filling valves, and supply culvert that would discharge into the lock through the upstream breast wall just above floor level. The existing emptying system would be retained or rebuilt. The third option, if both the filling and discharge culverts have to be condemned, would be to build a new lock. The results of the hydraulic model studies carried out to explore these three options are described.Key words: emergency closure, stop logs, follower, canal, lock, downpull, uplift, crane capacity, filling-emptying system, culverts.

In the winter of 1979/80, five petroleum companies participated in an Exxon Production Research Company program in which thirteen large-scale ice strength tests were conducted offshore in the vicinity of Prudhoe Bay. The purpose of the program was to determine the uniaxial compressive strength of annual sea ice as a function of strain rate and direction of loading with respect to preferred crystal alignment. Full ice sheet thickness test blocks with dimensions of 10 ft × 20 ft (3.05 m × 6.10 m) were cut free from the surrounding sheet ice. A hydraulic loading system with two million pounds of force capacity was used to compress the ice blocks at constant strain rates ranging from 10−7 s−1 to 10−5 s−1. Deformation in three orthogonal dimensions along with the axial had were measured and recorded throughout the test. This paper describes the field operations and test results, including uniaxial compressive strength, stiffness, Poisson’s ratio, and failure modes. Measured ice temperature, salinity and crystallographic structure are also presented.

In Greece biomass is often being disposed of uncontrollably, resulting in significant environmental impacts. The aim of this study is the single-stage anaerobic co-digestion assessment, valorizing Northern and Southern Greece mixtures, resulting from previous literature reviews, experimental designs, and biochemical methane potential (BMP) assays. Regarding the methane yield maximization, in Northern Greece, the most suitable mixture was 10% corn silage, 80% cattle manure, and 10% malt; while in Southern Greece it was 10% corn silage, 57% cattle manure, 23% orange peels, and 10% olive pomace for fall/winter season. The hydraulic retention time (HRT) was set at 20 d and an initial organic loading rate (OLR) of 2 g COD/(L·d) was applied, with a view to gradually increase it. However, volatile fatty acids accumulation was observed, which led to OLR reduction to 1.5 g COD/(L·d) for both experiments. The Northern Greece reactor operated successfully for OLR 1.5–5 g COD/(L·d), while further increase led to system failure. On the other hand, the reactor of the Southern Greece mixture operated successfully at OLR 1.5–2 g COD/(L·d), but further operation indicated inadequacy, probably due to inhibitor (such as limonene) accumulation. Mixtures consisting of corn silage, cattle manure, and malt can be successfully valorized at high OLR. However, further investigation for mixtures with orange peels is suggested due to the presence of inhibitors.

Eight cold-water streams in Lake and Geauga Counties, Ohio were evaluated to develop a revised predictive model to assess future streams for the introduction of threatened native Ohio Brook Trout (Salvelinus fontinalis). A 15-month study was conducted, ending May 2010, in streams where Brook Trout were previously introduced during the years 1997-2002. Fifty percent of the sixteen original reintroduction streams failed to support the establishment of self-sustaining populations of Brook Trout, indicating there were additional factors contributing to their success and failure. Of the 8 streams included in this study, 4 streams were designated successful, 2 variable, and 2 failed, in terms of the Brook Trout’s ability to establish self-sustaining populations by the Ohio Department of Natural Resources (ODNR). Multivariate statistical methods including Principal Component Analysis (PCA) and Agglomerative Hierarchical Cluster Analysis (AHCA) were implemented to determine the most important characteristics in Brook Trout stream selection. Factors found to be significant for Brook Trout success were stream velocities within the range of 1.4-4.7 cm/s, high hydraulic conductivity of the headwater bedrock aquifer (K>4.7 x 103 cm/s), lighter average δ18O ‰ (-9.8 to -10.4), either high percent canopy cover (40%-55%) or high percent instream cover (18%-37%), a high number of cold-water adapted benthic macroinvertebrate cold-water taxa (10-16 species), yearly average hyporheic water temperature of 4.6°C-17.2°C, average surface water turbidity of 7 to 31 NTU and long-term surface water temperature and dissolved oxygen monitoring over both winter and summer seasons is recommended prior to Brook Trout introduction to ensure their sustainability.

Abstract. Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity that is expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more complex, LSM hydrology models have not been widely evaluated against semi-arid ecosystem in situ data. We hypothesize that the failure of older LSM versions to represent evapotranspiration, ET, in arid lands is because simple bucket models do not capture realistic fluctuations in upper-layer soil moisture. We therefore predict that including a discretized soil hydrology scheme based on a mechanistic description of moisture diffusion will result in an improvement in model ET when compared to data because the temporal variability of upper-layer soil moisture content better corresponds to that of precipitation inputs. To test this prediction, we compared ORCHIDEE LSM simulations from (1) a simple conceptual 2-layer bucket scheme with fixed hydraulic parameters and (2) an 11-layer discretized mechanistic scheme of moisture diffusion in unsaturated soil based on Richards equations, against daily and monthly soil moisture and ET observations, together with data-derived estimates of transpiration / evapotranspiration, T∕ET, ratios, from six semi-arid grass, shrub, and forest sites in the south-western USA. The 11-layer scheme also has modified calculations of surface runoff, water limitation, and resistance to bare soil evaporation, E, to be compatible with the more complex hydrology configuration. To diagnose remaining discrepancies in the 11-layer model, we tested two further configurations: (i) the addition of a term that captures bare soil evaporation resistance to dry soil; and (ii) reduced bare soil fractional vegetation cover. We found that the more mechanistic 11-layer model results in a better representation of the daily and monthly ET observations. We show that, as predicted, this is because of improved simulation of soil moisture in the upper layers of soil (top ∼ 10 cm). Some discrepancies between observed and modelled soil moisture and ET may allow us to prioritize future model development and the collection of additional data. Biases in winter and spring soil moisture at the forest sites could be explained by inaccurate soil moisture data during periods of soil freezing and/or underestimated snow forcing data. Although ET is generally well captured by the 11-layer model, modelled T∕ET ratios were generally lower than estimated values across all sites, particularly during the monsoon season. Adding a soil resistance term generally decreased simulated bare soil evaporation, E, and increased soil moisture content, thus increasing transpiration, T, and reducing the negative bias between modelled and estimated monsoon T∕ET ratios. This negative bias could also be accounted for at the low-elevation sites by decreasing the model bare soil fraction, thus increasing the amount of transpiring leaf area. However, adding the bare soil resistance term and decreasing the bare soil fraction both degraded the model fit to ET observations. Furthermore, remaining discrepancies in the timing of the transition from minimum T∕ET ratios during the hot, dry May–June period to high values at the start of the monsoon in July–August may also point towards incorrect modelling of leaf phenology and vegetation growth in response to monsoon rains. We conclude that a discretized soil hydrology scheme and associated developments improve estimates of ET by allowing the modelled upper-layer soil moisture to more closely match the pulse precipitation dynamics of these semi-arid ecosystems; however, the partitioning of T from E is not solved by this modification alone.

In the technological line for the production of small diameter pipes used segment un-winder staffs with a cantilever drum and additional support. The experience of its operation has shown that one of its main shortcomings is the unsatisfactory operation of the hydraulic system clamping staffs. In the hydraulic clamping system of the staffs there are increased dynamic loads, which lead to the failure of components and elements of the hydraulic system. The layout of the hydraulic clamping system of the headquarters is made for design and technological rea-sons, without taking into account the influence of pipeline lengths on the nature of dynamic processes in the hydraulic system. In addition, the hydraulic system uses spool hydrodistributors with electro-hydraulic control, the operation time of which is practically not subject to regulation. Based on the analysis of known mathematical models for the study of dynamic processes in hydraulic systems, it was concluded that as a mathematical model that takes into account the design and operation of the hydraulic clamping system staffs finite-difference method in a sys-tem of ordinary differential equations with boundary conditions described by algebraic equations. A basic dynamic model has been created, which allows to analyze with high relia-bility the behavior of the hydraulic system of the clamping mechanism of the staff in the segment unwinder of the rolls, which is exposed to different nature in a wide range of mode parameters. Simulink MATLAB software environment was used to effectively solve this problem. During the implementation of the mathematical model, a study of the modes of operation of the hydraulic system of the clamping mechanism of the staff was performed. It was found that at the end of the working and reverse strokes of the clamping mechanism of the roll in the end posi-tions there are dynamic loads in the hydraulic system that reach the maximum allowable values. In addition, it was found that during the acceleration of the piston of the hydraulic cylinder during operation and reverse, although there are no dangerous loads, but there are rapid fluctuations in pressure in the cavities of the hydraulic cylinder. Theoretical studies of the modes of operation of the hydraulic clamping system of the staff in the segment unwinder with different operating times of the control valve. As a result of the study of transients in the unwinding hydraulic system with different operating times of the hydraulic distributor, its ra-tional operating time was recommended, which is 0.20 seconds when opening and 0.15 sec-onds when closing.

Discolouration is the greatest cause of customer dissatisfaction with drinking water quality, potentially masking other failures, including microbial issues, which can impact public health and well-being. The theorised association between biofilms (complex microbial communities) and discolouration within drinking water distribution systems (DWDS) was explored, whilst studying the impact and interactions of seasonal temperature variations and hydraulic regime. Transferability of findings to operational DWDS was ensured by using a temperature controlled, full-scale distribution experimental facility. This allowed isolation of the factors of interest, with integration of physical, chemical and microbial analyses. Greater discolouration and biofilm cell accumulation was observed under warmer (summer, 16°C) temperatures compared to cooler (winter, 8°C), evidence of microbiology being an important driver in DWDS discolouration behaviour. Temperature was generally more influential upon discolouration and biofilm cell volumes than the shear stress imposed by the hydraulic regimes, which included three steady state and two varied flow patterns. However, the trends were complex, indicating interactions between the two parameters in governing microbial accumulation and discolouration. These results are important in informing sustainable management of our ageing DWDS infrastructure to deliver safe high quality drinking water. By providing new evidence that discolouration is a biofilm/microbiologically-mediated process, we can better understand the importance of targeting interventions to hotter seasons, and manipulating hydraulic conditions (which we can control), to minimise the long-term impacts of impending changing climates on water quality.

This study focuses on hydraulic hoses utilized in the hydraulic systems of forklifts. The investigation examined 8 forklifts, each with a loading capacity of 10 tons. The check took place every six months over a three-year span. Before and after each shift, the forklift operator performed visual checks and hydraulic system and brake а inspections. The research findings indicated that the most frequent hose malfunction was a result of a rupture. The failure rate noticeably increased during the winter, attributable to the low temperatures' adverse effect on the hoses' physical and mechanical properties. Another common area of hydraulic hose failure is due to substandard crimping and minimal fitting depth in the sleeves..

Le Douglas, première essence de reboisement en région Auvergne-Rhône-Alpes et seconde au niveau nationale, est d'intérêt économique majeur en France avec 13 millions de plants produits par an. Un phénomène de rougissement - observé 1/3 hivers en France - affecte les jeunes Douglas (< 15 ans), pouvant atteindre jusqu'à 80% de la plantation. Un arbre rougissant n'a pas d'avenir sylvicole et meurt généralement dans l'année suivant le rougissement. Les objectifs de ma thèse ont été de donner une meilleure compréhension du rougissement hivernal à travers l'identification des paramètres climatiques déclenchant le rougissement mais surtout des mécanismes physiologiques induisant le rougissement de l'aiguille.Afin d'identifier l'aléa climatique critique, une synthèse approfondie basée sur la littérature, ainsi qu'une analyse bioclimatique ont été menées. La synthèse de littérature a permis d'identifier certaines conditions climatiques caractéristiques des années dites « à rougissement » à savoir des périodes anticycloniques en sortie d'hiver et/ou la succession de périodes froides et chaudes. La synthèse comme l'analyse bioclimatique en commun, ont identifié un cumul de variables climatiques à savoir des températures chaudes en journée, une forte amplitude thermique journalière, des vitesses de vent au moins modérées et une humidité de l'air relative. Les cycles gel-dégel avec des températures nocturnes froides ne ressortaient pas de l'analyse climatique alors qu'ils étaient mentionnés dans la littérature.Afin de comprendre comment un Douglas rougit, nous avons d'abord, souligné les lacunes de connaissances sur le rougissement hivernal et proposé des mécanismes potentiels pouvant, seuls ou en interaction, induire ce désordre physiologique à savoir ; 1) une sécheresse hivernale induisant des défaillances hydrauliques, 2) un stress photo-oxydatif et 3) une désacclimatation précoce. En conditions contrôlées, nous avons exposé des jeunes Douglas à une sécheresse hivernale à travers un différentiel thermique entre les racines et le houppier de l'arbre (TSOIL < 5°C ; TMOY_AIR ~ 14°C). Une partie d'entre eux a été exposée à des intensités lumineuses susceptibles d'induire un stress photo-oxydatif (> 1800 PPFD). Les températures froides du sol ont induit un stress hydrique modéré en limitant l'absorption d'eau racinaire alors que les températures chaudes de l'air ont favorisé les pertes hydriques au niveau des aiguilles. Cependant, le Douglas a pu s'acclimater à ce nouvel environnement en reprenant même leur croissance. L'exposition à une intensité lumineuse élevée n'a pas généré de dommages irréversibles sur le PSII, ni de stress photo oxydatif. Aucun rougissement du Douglas n'a pas été observé - invalidant l'hypothèse 2 mais partiellement la 1, le houppier n'ayant été exposé à aucune contrainte gélive. In natura, nous avons mesuré en continu de décembre 2020 à juin 2023 les variations de diamètre de jeunes douglas couplées avec les températures/hygrométrie de quatre parcelles dans le Massif Central. Les gels printaniers d'avril 2021 sur des Douglas désacclimatés n'ont pas été suivi de rougissement de l'aiguille ni de dommages cambiaux, ce qui n'a pas permis de valider l'hypothèse 3. Néanmoins, la comparaison d'un hiver sans rougissement (2021) avec un hiver à rougissement (2022) a permis de souligner une forte contrainte hydrique générée depuis l'apex, en lien avec une période anticyclonique en janvier 2022. La défaillance hydraulique serait favorisée par une transpiration quotidienne à laquelle s'ajoutent des cycles gel-dégel qui amplifient la contrainte hydrique et créent des défaillances hydrauliques dans le houppier, pouvant expliquer le dessèchement et le rougissement de l'aiguille. Ainsi, nous retiendrons l'hypothèse 1, qu'il faudrait tester en conditions contrôlées
The Douglas fir is the first reforestation species in the Auvergne-Rhône-Alpes region and the second in France as a whole, and is of considerable economic importance in France, where 13 million trees are produced each year. Winter reddening affects young Douglas-fir (< 15 years old), affecting up to 80% of the plantation. A reddening tree has no silvicultural future and typically dies within a year after reddening. The objectives of my PhD thesis were to have a better understanding of winter reddening by identifying the climatic parameters that trigger reddening and, more importantly, the physiological mechanism(s) that cause needle reddening.A thorough literature review and bioclimatic analysis were undertaken to identify critical climatic factors. The literature synthesis identified certain climatic conditions characteristic of 'reddening' years, including anticyclonic periods after winter and/or alternating cold and warm periods. Both the literature synthesis and the bioclimatic analysis identified a combination of climatic variables: warm daily temperatures, high daily temperature amplitude, at least moderate wind speeds and relative humidity. However, the freeze-thaw cycles with cold night temperatures did not emerge from the climate analysis, although they are mentioned in the literature.In order to understand how Douglas fir reddens, we first identified gaps in our knowledge of winter reddening and proposed potential mechanisms, either single or interacting, that cause this physiological disorder: 1) winter drought leading to hydraulic failure, 2) photo-oxidative stress, and 3) premature deacclimation. Under controlled conditions, young Douglas fir trees were exposed to winter drought through a temperature differential between roots and canopy (TSOIL < 5°C; TMOY_AIR ~ 14°C). Some of these trees were exposed to light intensities that could induce photooxydative stress (> 1800 PPFD). Cold soil temperatures induced moderate water stress by limiting root water uptake, while warm air temperatures caused water loss at the needle level. However, Douglas fir was able to acclimate to this new environment and even resumed growth. Exposure to high light intensity did not cause irreversible damage to PSII or photooxydative stress. No reddening of the Douglas fir was observed, thus refuting hypothesis 2, but partially supporting hypothesis 1, as the canopy was not exposed to freezing stress. In the field, continuous measurements of young Douglas fir diameter variation were coupled with temperature/humidity measurements from four plots in the Massif Central from December 2020 to June 2023. Spring frosts in April 2021 on deacclimated Douglas fir did not result in needle reddening or cambial damages, thus failing to validate hypothesis 3. Nevertheless, comparison of a asymptomatic winter (2021) with a asymptomatic winter i.e. with winter reddening (2022) revealed significant hydraulic stress generated from the apex, associated with an anticyclone period in January 2022. Hydraulic failure could be exacerbated by daily transpiration, combined with freeze-thaw cycles that increase hydraulic stress, leading to canopy hydraulic failure that could explain needle desiccation and reddening. We therefore favour hypothesis 1, which should be tested under controlled conditions

AbstractOur study focuses on a slow-moving landslide in the Thompson River valley, south-central British Columbia, Canada, that has posed a hazard to the national railway transportation corridor since 1880. Real-time kinematic global navigation satellite systems, unoccupied aerial vehicles, and satellite synthetic aperture radar interferometry time-series show significant displacement encroaching on railway infrastructure. In this paper, geospatial relationships between landslide distribution and specific terrain features, and the environmental conditions triggering instability are determined from field-based geological observations. We describe how earth material stratigraphy, textures, and penetrative planar structures are important controls on sub-surface drainage, and how these factors influence the style, timing, and rate of slope displacement. West of the railway tracks, slide scarps extend across the toe slope, corresponding to narrow zones of high displacement, presence of perennial springs and seepage, and cutbank erosion along the river channel. Fluvial incision exposes weak, failure-prone units at the base of the fill sequence, and with ongoing channel migration promotes instability by altering landslide toe geometry. Currently, the zone of potential displacement does not extend upslope into the inactive (1880) main slide body, east of the tracks. Seasonal variations in hydrogeological conditions influence the spatial and temporal patterns of surface water and groundwater flow, in turn controlling the distribution of translational-rotational displacement of slide blocks, and rates of movement on reactivated shear surfaces that extend under Thompson River. Slope failure occurs along weak, sub-horizontal shear zones within poorly drained glaciolacustrine clay and silt units, overlain by rapidly drained glaciofluvial outwash gravel, and imperfectly drained till diamicton. River levels exert a complex control on landslide stability, influencing hydraulic gradients within the basal glaciolacustrine unit, particularly along rupture surfaces within it. Ground displacement occurs while river levels are at their lowest between February and March, before peak flows in June, or after July until December while storm-fed river levels progressively lower to the next winter minimum. Groundwater levels remain elevated in the slide body throughout the year, contained in porous gravel and sand beds, and along brittle fractures and sub-horizonal shear zones in silt-clay varve beds. Geospatial and temporal change-detection monitoring of active landslides and at-risk infrastructure, when benchmarked with terrain and hydrogeological observations, is a cost-effective hazard management practice that provides important geoscience information to help develop appropriate early warning, mitigation, adaptation, and risk reduction measures.

ABSTRACT The very low permeability of intact salt rocks makes them promising media for the geologic disposal of nuclear waste. However, permeating flow can occur through fractures in rock salt. These fractures can be induced by excavation operations that create a localized damage rock zone where brine could migrate towards the excavation, or by strong temperature changes, around a high-heat emitting nuclear waste package, causing compressive (during heating) or tensile (during cooling) thermal stresses that could cause rock salt damage and a potential brine migration towards the heat source. Coupled thermo-hydro-mechanical simulations were performed to predict quantitatively the brine flow into a borehole excavated in rock salt as a result of excavation, heating/cooling and damage. The rate of water release was shown to rise with any change in temperature, with the greatest increase occurring during the cooling phase. Heating-induced compressive thermal stresses and creep caused the initial mechanical damage of rock salt, leading to the creation of higher-permeability zones (e.g., fractures) for pore water flow. The subsequent cooling led to an enhancement of these zones and the formation of additional ones as a result of tensile rock failure. INTRODUCTION Rock salt has been identified as a suitable medium for nuclear waste disposal due to its low permeability, high thermal conductivity, and self-sealing capacity (Sweet and McCreight, 1983; Cosenza et al., 1999; Winterle et al., 2012). However, micro-fractures in the salt host rock can compromise the hydraulic integrity of the disposal facility by providing pathways for brine migration (Hansen and Leigh, 2011). Micro-fracturing is often initiated by two phenomena: shear-induced dilatancy (Stormont, 1997) and tensile stresses exceeding the tensile strength of salt which is around 1 MPa (Hoffman and Ehgartner, 1998). Several laboratory and in situ tests have been conducted in the 1990s or earlier to characterize the movement of brine in rock salt under isothermal and heated conditions (Hohlfelder and Hadley, 1979; Hohlfelder, 1980; Ewing, 1981; Krause, 1983; McTigue and Nowak, 1987; Finley et al., 1992). In the absence of heating, the brine inflow response varies from one experiment to another, mainly due to the heterogeneity of the tested rock salt formation that the excavation intersects (Finley et al., 1992). In the presence of a heating phase, the experiments show that brine inflow rates increase with an increasing borehole temperature (Hohlfelder and Hadley, 1979; Hohlfelder, 1980; Ewing, 1981; McTigue and Nowak, 1987). Additionally, some of these tests have shown that a considerable amount of brine was released during the heater shut-down (Hohlfelder and Hadley, 1979; Ewing, 1981).