Storage tank | EPFL Graph Search

Storage tanks are containers that hold liquids, compressed gases (gas tank; or in U.S.A "pressure vessel", which is not typically labeled or regulated as a storage tank) or mediums used for the short- or long-term storage of heat or cold. The term can be used for reservoirs (artificial lakes and ponds), and for manufactured containers. The usage of the word tank for reservoirs is uncommon in American English but is moderately common in British English. In other countries, the term tends to refer only to artificial containers. In the USA, storage tanks operate under no (or very little) pressure, distinguishing them from pressure vessels. Storage tanks are often cylindrical in shape, perpendicular to the ground with flat bottoms, and a fixed frangible or floating roof. There are usually many environmental regulations applied to the design and operation of storage tanks, often depending on the nature of the fluid contained within. Above-ground storage tanks (ASTs) differ from undergrou

Determination of variables influencing the effectiveness of disinfection of surface water used for human consumption in Costa Rica

Clara Barret

Disinfection of water for human consumption is a challenge to ensure that water is free of pathogens and pollutants while avoiding the formation of potentially harmful undesirable products. The establishment of disinfection facilities must take into account the local context as well as technical and economic feasibility to ensure their sustainability. Chlorination is a disinfection technique that is widely used throughout the world and can take several forms. However, this technique can lead to the formation of disinfection by-products, some of which are harmful to human health and are a source of growing concern. This present report focuses on chlorination using tablets that release chlorine when eroded by contact with water. This study aimed at improving the understanding of the effect of various parameters on the efficiency of water chlorination in the Cartago region (Costa Rica). First a chlorination facility located in a village near Cartago was studied. The purpose of this assessment was to diagnose the current situation, determine the changes needed to improve it and implement them. It was showed that the chlorine concentration delivered by this facility was too low and variable. A new chlorinator and a tank allowing a better mixing of the chlorinated solution have been installed. These modifications have resulted in a higher and more homogeneous chlorine concentration in the storage tanks and an improvement in some water quality parameters. On the basis of the results, recommendations were made to ensure the proper functioning of the facility and the continuation of measurements during future campaigns. It should be noted that this was a short-term study, measurements over a longer period would allow more precise conclusions to be drawn. The second part of the project concerned 10 chlorination facilities in the Cartago region. The purpose was to compare the results of various parameters of surface and groundwater samples collected in the rainy/transition season in 2018 with those of the 2019 dry season. For the moment there were thus only two series of data but this has nevertheless allowed us to observe an improvement in certain parameters during the dry season. Future measurements campaigns will consolidate these results.

2019

Experimental Determination of the Capacity of Wall-to-Base Connections in Storage Tanks

Gustavo Cortes, Eric Lattion, Alain Nussbaumer

Earthquakes around the world have affected many unanchored tanks used for storage of gasoline. When these unanchored tanks are subjected to strong motion, the moment generated at the base, by the mass of liquid contained in the tank, will cause partial uplift of the base (i.e. rocking of the tank), inducing cycles of rotation at the wall-to-base connection. Actual codes of standard practice used in Europe and New Zealand limit the rotation that may be allowed at this connection to 0.2 radians. This limit was based on a series of assumptions since no realistic tests had been conducted. This paper presents the experimental research conducted to determine the real rotational capacity of these connections. The tests were carried out considering the bending stresses and the membrane stresses that develop at the base plate when uplift occurs. Specimens from an old existing tank (dismantled) were used. New specimens were also fabricated and used to allow for a more comprehensive study. Results from this research are presented in the form of plots of maximum rotation vs. number of cycles to failure, called RN curves. These curves revealed that the current Eurocode limit of 0.2 radians is overly conservative. Based on the limited data, a limit of 0.4 radians would be more realistic.

Elsevier2011

Experimental Study on the Seismic Behavior of Shell-Base Connections in Large Storage Tanks

Gustavo Cortes, Alain Nussbaumer

When an unanchored tank is subjected to strong motion, the impulsive mass of the contained liquid generates a moment which if strong enough could cause partial uplifting of the base plate. As the tank undergoes uplifting, the shell-base welded connection is subjected to cycles of rotation which could lead to its failure. To address this issue, the Eurocode and the New Zealand’s recommendations limit the rotation amplitude that the shell-base connection of a tank may undergo to 0.2 radians. This limit is obtained from the following two assumptions: (1) a plastic hinge with a length equal to twice the thickness of the base plate forms at the base plate, next to the connecting weld, and (2) the maximum strain that can be sustained by the base plate is 5%. While these two assumptions are reasonable and have been the state of practice for many years, no research work is believed to exist backing these two assumptions and therefore the 0.2 radians limit. For this reason, an experimental research was conducted to determine the real rotational capacity of shell-base welded connections found in tanks. A total of 24 shell-base connections were tested considering the bending and membrane stresses that develop at the base plate when uplift occurs. Constant amplitude tests were carried at different amplitudes of rotation in order to create curves of rotation versus number of cycles to failure. The main finding from this investigation is that the current limit of 0.2 radians is very conservative and that a limit of 0.4 radians would be more realistic.

2011

Determination of variables influencing the effectiveness of disinfection of surface water used for human consumption in Costa Rica

Clara Barret

2019