CA2978297A1 - Water storage containers exhibiting reduced corrosion, and devices and methods for reducing rate of corrosion in water storage containers - Google Patents

Abstract

A water storage tank includes: a tank containing water; a roof positioned over the tank; a headspace region formed between the roof and a surface of the water contained in the tank;
and a corrosion reduction system. The corrosion reduction system includes (i) a port that enables air to flow out of the water storage tank, and (ii) an active air ventilation system having at least one device configured to facilitate movement of air exterior of the water storage tank into the headspace region. The corrosion reduction system reduces a rate of corrosion of the water storage tank. A method of reducing a rate of corrosion of a water storage tank is also included.

Description

WATER STORAGE CONTAINERS EXHIBITING REDUCED CORROSION, AND
DEVICES AND METHODS FOR REDUCING RATE OF CORROSION IN WATER
STORAGE CONTAINERS
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of United States Provisional Application No.
62/384,074, filed September 6, 2016, which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention

[0002] The present invention is directed to water storage containers that provide reduced corrosion rates, and devices and methods of reducing corrosion rates in storage containers.
Description of Related Art

[0003] Elevated storage containers and other large water storage containers are an integral part of many municipal water distribution systems. These containers are intended to ensure adequate hydrostatic pressure to enable effective water delivery and to store water hygienically. Water storage tanks also provide relief from water surges and provide emergency supplies for fire and other emergencies. As components of municipal water systems, these containers are expected to have long, useful lives, often from 15 to 25 years, or 50 years or greater.

[0004] Achievement of the expected long lifespans of water storage tanks is made difficult by the very nature of their structure and function. For example, water storage tanks are often made of steel, which is subject to corrosion that will eventually cause failure of the storage tanks. Water storage tanks may be particularly susceptible to corrosion because interior tank temperatures are often in excess of exterior air temperatures in that the steel (or concrete) structure absorbs heat from the sun and re-radiates the heat into the interior of the tank and, with a volume that holds large amounts of water, the interior humidity ("RH") inside a water storage tank is almost always 100%. Furthermore, the drinking water (and water held for other processes) is often treated with disinfectant chemicals, such as chlorine, that produces vapors which can also accelerate corrosion rates.

[0005]
Forced air ventilation is a process of controlling the interior humidity of enclosed structures (buildings, storage vessels). However, when controlling interior conditions to lower rates of corrosion, it has commonly been assumed that ventilating exterior atmosphere into an enclosed structure is counter-productive. For example, corrosion-susceptible equipment is commonly stored in an enclosure that prevents the ingress of outside air. In extreme cases (e.g.
the storage of military equipment in tropical climates), structures are built that include active de-humidification.

[0006] Typically, water storage tanks are designed to minimize the exchange of air with the outside. However, it is appreciated that at least some air must be exchanged as water levels rise or fall within the tank (for example in order to prevent de-pressurization of the tank during draining and buckling of the tank structure). Beyond permitting the minimum amount of air required to equilibrate air pressure inside the tank, no further ventilation is desired.
In fact, excess ventilation/air access/air exchange is viewed as a liability because additional air vents are: (i) potential sources of sanitary defects and can increase the risk of contamination of the interior of the tank by the outside (e.g. bird droppings, insects, dust); and (ii) allow greater air exchange inside the tank and accelerate interior corrosion.

[0007] A common approach to controlling corrosion of water storage tanks is to coat the interior surfaces of the water storage tanks with epoxy paints to prevent direct exposure of the steel to corrosion-inducing conditions. However, 100% coverage with no gaps is essentially impossible to achieve. Even if a complete epoxy coating is achieved, the coating will be subject to stresses due to thermal cycling of the structure which will produce cracks in the coating, thereby allowing the underlying steel to become exposed to air or water that causes corrosion.
Similarly, VOC-compliant coatings are not as resilient and must be reapplied more frequently.
Coating performance has also been reduced by the requirements to remove toxic materials, such as lead, from the coatings. Thus, coating failure is a common problem in water storage containers and reapplication on a regular basis of these coatings is necessary.

[0008] Further, reapplication of a coating during tank interior refurbishment is prone to even greater potential for gaps. For example, tight corners and areas where roof panels rest atop beams, but which are not seal-welded, are not accessible for recoating and are susceptible to corrosion.
Moreover, the ideal time to reapply the coating materials is in the summer months such that routine maintenance is necessary just at the time the water storage tanks are needed most.

[0009] It is also appreciated that not all surfaces are subjected to the same conditions.
Most facilities focus on protection of water storage tank interiors where liquid water is in contact with the surface. The coatings best to protect water container interior surfaces from corrosion where liquid water is in contact are not necessarily the same as those best to protect surfaces from vapors that comprise corrosive chemicals. The areas exposed to chemical vapors is often referred to as headspace. Further, headspace volume will fluctuate according to the amount of water stored in the tank at various times. Thus, it is difficult, if not impossible, to apply different coatings to the various portions of the interior of the water storage tank and achieve satisfactory corrosion proofing.

[0010] Thus, it is desirable to provide water storage tanks having a headspace region with a reduced propensity to corrode and which do not require additional maintenance and costs to reduce such corrosion overtime.
SUMMARY OF THE INVENTION

[0011] In certain non-limiting and preferred embodiments, the present invention is directed to a water storage tank comprising: a tank containing water; a roof positioned over the tank; a headspace region formed between the roof and a surface of the water contained in the tank; and a corrosion reduction system comprising: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into the headspace region, in which the corrosion reduction system reduces a rate of corrosion of the water storage tank.

[0012] In some non-limiting and preferred embodiments, the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region in a direction that is non-perpendicular to the water surface. The device of the active air ventilation system can also be configured to facilitate the movement of air exterior of the water storage tank into the headspace region substantially laterally across an interior surface of the roof.

[0013] In certain non-limiting and preferred embodiments, the device of the active air ventilation system comprises air vent openings that fluidly connect the air exterior of the water storage tank to the headspace region. The device of the active air ventilation system can further comprise at least one screen that is positioned over at least one of the air vent openings.

[0014] In some non-limiting and preferred embodiments, the active air ventilation system further comprises an air-moving device that facilitates an exchange of air between an interior and exterior of the water storage tank. The active air ventilation system can also comprise a deflector that directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof. In some non-limiting and preferred embodiments, the active air ventilation system includes both an air-moving device and a deflector. In such embodiments, the deflector is in fluid communication with the air-moving device, and the deflector directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

[0015] In certain non-limiting and preferred embodiments, the water storage tank further comprises a mixing device configured to bring cooler water to a top portion of the tank. Further, at least a portion of the water storage tank and/or at least a portion of an interior of the roof can be formed from a material that is prone to corrosion. The material that is prone to corrosion can comprise a metal.

[0016] In some non-limiting and preferred embodiments, the corrosion reduction system of the present invention reduces the rate of corrosion of the water storage tank by at least about 10% to at least about 90% as measured by ASTM G50-10(2015).

[0017] In certain non-limiting and preferred embodiments, the present invention is also directed to a method of reducing a rate of corrosion of a water storage tank comprising actively exchanging air outside of the water storage tank with air inside the water storage tank with a corrosion reduction system to reduce the rate of corrosion of the water storage tank, in which the corrosion reduction system comprises: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into a headspace region formed between a roof positioned over the water storage tank and a surface of water contained in the tank.

[0018] In some non-limiting and preferred embodiments, the corrosion reduction system is retrofitted into the water storage tank. In certain non-limiting and preferred embodiments, the water storage tank comprises a mixing device, and the method further comprises actively mixing with the mixing device such that cooler water is brought to a top of the water storage tank. It is appreciated that the water storage tank used in the method of the present invention can also comprise any of the previously described features.

[0019] In certain non-limiting and preferred embodiments, the corrosion reduction system reduces air temperature, humidity, and levels of oxidizing vapors in the headspace region of the tank. In addition, the method of the present invention reduces the rate of corrosion of the water storage tank by at least about 10% to at least about 90% as measured by ASTM
G50-10(2015).

[0020] The present invention is also directed to the following clauses.

[0021] Clause 1: A water storage tank comprising: a tank containing water; a roof positioned over the tank; a headspace region formed between the roof and a surface of the water contained in the tank; and a corrosion reduction system comprising: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into the headspace region, wherein the corrosion reduction system reduces a rate of corrosion of the water storage tank.

[0022] Clause 2: The water storage tank of clause 1, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region in a direction that is non-perpendicular to the water surface.

[0023] Clause 3: The water storage tank of clauses 1 or 2, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region substantially laterally across an interior surface of the roof.

[0024] Clause 4: The water storage tank of any of clauses 1 to 3, wherein the device of the active air ventilation system comprises air vent openings that fluidly connect the air exterior of the water storage tank to the headspace region.

[0025] Clause 5: The water storage tank of clause 4, wherein the device of the active air ventilation system comprises at least one screen that is positioned over at least one of the air vent openings.

[0026] Clause 6: The water storage tank of any of clauses 1 to 5, wherein the active air ventilation system further comprises an air-moving device that facilitates an exchange of air between an interior and exterior of the water storage tank.

[0027] Clause 7: The water storage tank of any of clauses 1 to 6, wherein the active air ventilation system comprises a deflector that directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

[0028] Clause 8: The water storage tank of clause 6, wherein the active air ventilation system comprises a deflector that is in fluid communication with the air-moving device, and wherein the deflector directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

[0029] Clause 9: The water storage tank of any of clauses 1 to 8, further comprising a mixing device configured to bring cooler water to a top portion of the tank.

[0030] Clause 10: The water storage tank of any of clauses 1 to 9, wherein at least a portion of the water storage tank and/or at least a portion of an interior of the roof is formed from a material that is prone to corrosion.

[0031] Clause 11: The water storage tank of clause 10, wherein the material that is prone to corrosion comprises a metal.

[0032] Clause 12: The water storage tank of any of clauses 1 to 11, wherein the corrosion reduction system reduces the rate of corrosion of the water storage tank by at least about 10% to at least about 90% as measured by ASTM G50-10(2015).

[0033] Clause 13: A method of reducing a rate of corrosion of a water storage tank comprising actively exchanging air outside of the water storage tank with air inside the water storage tank with a corrosion reduction system to reduce the rate of corrosion of the water storage tank, wherein the corrosion reduction system comprises: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into a headspace region formed between a roof positioned over the water storage tank and a surface of water contained in the tank.

[0034] Clause 14: The method of clause 13, wherein the corrosion reduction system is retrofitted into the water storage tank.

[0035] Clause 15: The method of clauses 13 or 14, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region in a direction that is non-perpendicular to the water surface.

[0036] Clause 16: The method of any of clauses 13 to 15, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region substantially laterally across an interior surface of the roof.

[0037] Clause 17: The method of any of clauses 13 to 16, wherein the active air ventilation system further comprises an air-moving device that facilitates an exchange of air between an interior and exterior of the water storage tank.

[0038] Clause 18: The method of clause 17, wherein the active air ventilation system comprises a deflector that is in fluid communication with the air-moving device, and wherein the deflector directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

[0039] Clause 19: The method of any of clauses 13 to 18, wherein the water storage tank comprises a mixing device, and wherein the method further comprises actively mixing with the mixing device such that cooler water is brought to a top of the water storage tank.

[0040] Clause 20: The method of any of clauses 13 to 19, wherein the corrosion reduction system reduces air temperature, humidity, and levels of oxidizing vapors in the headspace region of the tank.

[0041] Clause 21: The method of any of clauses 13 to 20, wherein the method reduces the rate of corrosion of the water storage tank by at least about 10% to at least about 90% as measured by ASTM G50-10(2015).
BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG.
1 is a partial front view of a roof portion of a water storage tank having a corrosion-reduction system according to a non-limiting embodiment of the invention; and

[0043] FIG. 2 is a cross-sectional front view of the anti-corrosion device shown in FIG. 1.
DESCRIPTION OF THE INVENTION

[0044] For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about".
Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0045] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

[0046] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

[0047] Further, the terms "upper," "lower," "right," "left," "vertical,"
"horizontal," "top,"
"bottom," "lateral," "longitudinal," and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the specification, are simply exemplary embodiments of the invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting.

[0048] In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of "or" means "and/or" unless specifically stated otherwise, even though "and/or" may be explicitly used in certain instances.

[0049] The phrases "water storage tanks", "water storage containers", "water-containing storage tanks" and the like are used interchangeable and mean the same thing. In addition the term "water"
when used to describe "water storage tanks/containers" encompasses both water and compositions comprising water, in which water is the majority of the composition.

[0050] The present invention relates to systems and methods for reducing the rate of corrosion in the headspace region of water-containing storage tanks, such as municipal water storage tanks for example. Although the systems and methods are non-coating based, the systems and methods of the present invention may be used together with coating-based approaches for reducing the rate of corrosion. As such, the systems and methods of the present invention may be used with coating-based water storage tanks or non-coating based water storage tanks. In general, the systems and methods of the present invention are designed to reduce at least one of the temperature, humidity, and levels of oxidizing vapors in the interior of the water storage tanks, for example by actively exchanging air from outside the tank with air inside the tank. In some non-limiting and preferred embodiments, the system reduces temperature and humidity levels in the interior of the water storage tank. In some other non-limiting and preferred embodiments, the system reduces temperature, humidity and oxidizing vapor levels in the interior of the water storage tank.

[0051] The present invention also relates to water-storage tanks, including municipal water-storage tanks, fitted or retrofitted with non-coating based corrosion-reduction systems that provide a reduced rate of corrosion. The corrosion-reduction system is an active ventilation system adapted for use with a water storage tank. In certain non-limiting and preferred embodiments, the active ventilation system is configured to move air in a direction that is non-perpendicular to the surface of the water in the storage tank, which surface defines a boundary of the headspace region. In certain further non-limiting and preferred embodiments, the active ventilation system is configured to move air laterally (substantially laterally) across the roof of the water storage tank.

[0052] In some non-limiting and preferred embodiments, the water-containing storage tank 100 of the present invention is a municipal water storage tank. Municipal water storage tanks typically have a capacity of about 500 gallons of water or greater, or about 1000 gallons of water or greater, or about 100,000 gallons of water or greater, or about 1,000,000 gallons of water or greater.
Smaller water storage tanks (for example, having a capacity of 500 gallons or less) may be made from non-corrosive materials such as plastic. Larger storage tanks, on the other hand, typically comprise materials that are susceptible to corrosion such as metal (for example steel). The systems and devices of the present invention can be used with water-containing storage tanks 100 that are made of various materials including, but not limited to, the previously described materials. The systems and devices of the present invention are particularly useful when used with water-containing storage tanks comprising interior surfaces made at least partially from materials susceptible to corrosion such as a metal, regardless of whether the surface is protected by a corrosion-resistant coating.

[0053] In certain non-limiting and preferred embodiments, referring to FIG. 1, the water-containing storage tank 100 comprises a headspace region 5 formed between a roof portion 3 and the surface of the water contained in the water-containing storage tank 100.
As used herein, the term "headspace region" refers to a region in a water-containing storage tank 100 that does not contain water. It is appreciated that the volume of headspace region 5 fluctuates with respect to the amount of water stored in the water-containing storage tank 100.

[0054] The headspace region 5 is particularly vulnerable to corrosion since the interior conditions inside a water storage tank 100 are often worse (in terms of corrosion rates) than conditions outside the tank. For example, interior air temperatures are often greater than exterior air temperatures because the tank 100 materials (e.g. steel or concrete) absorb heat from the sun and re-radiate the heat into the interior of the tank 100. Furthermore, with a volume that holds large amounts of water, the interior humidity ("RH") inside a water storage tank 100 is almost always 100%. That is, air in the headspace region 5 generally exhibits a higher relative humidity than air on the exterior of the tank 100. The drier exterior air induces vapor flow from the water surface into the headspace region 5. Because drinking water (and water held for other processes) is often treated with disinfectant chemicals such as chlorine (a powerful oxidizer), the vapors will include such disinfectant chemicals that further accelerate corrosion rates.
In locations with low relative humidity and high daytime temperatures, such as in the U.S.
Southwest, it can be expected that corrosion-inducing vapors will be more prevalent because more evaporation will occur under these conditions. However, it is appreciated that corrosion from water vapors occurs in water-containing storage tanks 100 located in other geographic regions because, under most environmental conditions, evaporation of water stored in the tank 100 will occur.

[0055] In accordance with the present invention, and as shown in FIGS. 1 and 2, the water storage tank 100 is fitted with a corrosion reduction system 50 comprising a port 1 and an active air ventilation system 2. As used herein, a "corrosion reduction system"
refers to a system that reduces the rate of corrosion of a target water storage tank 100. As such, water-containing storage tanks 100 comprising the corrosion-reduction systems 50 of the present invention exhibit a reduced rate of corrosion as compared to similar water-containing storage tanks 100 without the corrosion-reduction systems 50. The water storage tanks 100 may be originally manufactured with the corrosion-reduction system 50, or may be retrofitted to include corrosion-reduction systems 50.

[0056]
Further, the port 1 and an active air ventilation system 2 enter or are in fluid communication with the headspace region 5. For example, and as shown in FIGS.
1 and 2, the port 1 and an active air ventilation system 2 are positioned through the roof 3 of the water containing storage tank 100 such that the port 1 and the active air ventilation system 2 are in fluid communication with the headspace region 5.

[0057] In general, current water-containing storage tanks 100 are designed to minimize exchange of air to only that which is necessary to equilibrate the air pressure. By contrast, the active air ventilation system 2 of the corrosion reduction system 50 of the present invention is configured to increase ventilation/air access/air exchange beyond that required to equilibrate air pressure in the tank 100, for example by lowering the temperature, humidity, and/or levels of oxidizing vapors in the interior of the water storage tank 100.

[0058] In some non-limiting and preferred embodiments, the corrosion reduction system 50 permits powered introduction of exterior air 6 into the headspace region 5 of the water storage tank 100. In certain embodiments, the water-storage tanks 100 may exist with installed volatile organic chemical ("VOC") reduction devices such as described in U.S. Patent Application Publication No.
2015-0167993, which is hereby incorporated by reference in its entirety, and which may serve the function of the air ventilation system 2 for the present corrosion-reduction system 50. In some non-limiting and preferred embodiments, the corrosion reduction system includes at least the port 1, the active ventilation system 2, and a (re)-configuration of the active ventilation system 2 to reduce the rate of corrosion as compared to a water storage tank having only the VOC
device installed.
For example, the rate of corrosion may be reduced by modifying the angle at which the VOC
device is installed and/or including a deflector 4 as shown in FIG. 2 with the corrosion reduction system 50 to direct airflow from the exterior of the tank 100 into the headspace region 5 in a direction that is non-perpendicular to the surface of the water in the tank 100. In some non-limiting embodiments, air is directed from the exterior laterally along the interior surface 12 of the roof of the tank 100.

[0059] In certain non-limiting and preferred embodiments, and referring to FIG. 2, the corrosion reduction system 50 includes an active ventilation system 2. The active ventilation system 2 is configured to control one or more parameters influencing air exchange including airflow rate, airflow direction, and frequency of active exchange (e.g. constant or intermittent) and, contrary to current teachings and understandings, the active ventilation system 2 is configured to increase ventilation/air access/air exchange beyond that required to equilibrate air pressure in the tank, for example by lowering the temperature, humidity, and/or levels of oxidizing vapors in the interior of the water storage tank. In some non-limiting embodiments, the active ventilation system 2 is configured to accomplish at least approximately 5 to 10 air exchanges/day. For example, for a 1MG tank with approximately 15 feet of headspace, a minimum of 5 to 10 air exchanges per day would correspond to 250 to 500 cfm.

[0060]
Referring to FIG. 2, the active ventilation system 2 comprises a ventilation device 8, which impacts airflow rate and frequency, and optionally a deflector 4, which impacts airflow direction. The ventilation device 8 is configured to facilitate exchange of air exterior 6 to the water storage tank 100 with air interior to the water storage tank 100 by fluidly connecting the interior headspace region 5 with the exterior environment by way of air vent openings 9. To alleviate and/or prevent contamination of water stored within the tank 100, for example to alleviate or prevent ingress of animals, leaves and/or other debris into the tank 100, screens 10 may be provided to cover the vent openings 9. In addition, the active ventilation system 2 is an "active" system, and accordingly provides input energy (e.g. mechanical or electrical) to assist the air exchange process.
In certain non-limiting and preferred embodiments, the input energy is provided by an air-moving device 11 such as a fan. In some non-limiting embodiments, for example where there may be a desire to achieve additional energy savings, a humidity switch may be included which automatically shuts off the air-moving device 11 if the interior humidity falls below a pre-determined amount such as below 100%.

[0061] The air-moving device 11 specifications and the dimensions of the air ventilation device 8, including the relative dimensions of the air ventilation device 8 as compared to the air-moving device 11, determine the airflow rate (or range of airflow rates). It is appreciated that the angle of the device 8 connected to the water storage tank 100 relative to the surface of water defining the lower boundary of the headspace region 5 will impact airflow direction.
Although the air-moving device 11, in this example a fan, is shown in FIG. 2 mounted within the ventilation device 8 formed on the roof 3 of the water storage tank 100, it need not be mounted on the roof 3 or in the device 8, but, for example, could be ducted from the ground.

[0062] In certain non-limiting and preferred embodiments, a deflector 4 may be used in connection with the air ventilation device 8 to control the airflow direction.
The use of a deflector 4 may be desirable where the airflow direction is otherwise perpendicular to the water surface 12.
Generally, the rate of corrosion is reduced as the direction of airflow is closer to lateral movement across the interior surface 12 of the roof 3 of the water storage tank 100.

[0063] In use, and without wishing to be bound by theory, the corrosion-reduction systems 50 according to the present invention lowers the temperature, humidity, and/or oxidizing vapor levels by active ventilation alone (exchanging tank air with the outside air), or by combining active ventilation with active mixing (not shown) (which brings cooler water to the top of the tank 100, lowering air temperature and humidity levels), or by active mixing alone (which lowers the headspace region 5 temperature by bringing cooler water to the surface). That is, the corrosion-reduction systems 50 according to the present invention, reduce the propensity of the interior surface of the water storage tank 100 at the headspace region 5 to corrode, for example by engaging an air-moving device 11 that is in fluid communication with the interior and the exterior of the tank 100 to circulate air within the headspace region 5, thereby reducing the relative humidity of the headspace region 5 and/or enabling at least some of the corrosion-inducing vapors to exit through one or more ports 1 positioned in the headspace region 5 (for example the upper portion of the headspace region 5), where the one or more ports 1 serve to vent vapors from the headspace region 5 to the exterior of the water storage tank 100 and/or to charge the headspace region 5 with exterior air, which may serve to reduce the concentration of corrosion-inducing vapors in the headspace region 5. Such lower concentration of vapors (and lower temperature) results in a reduced rate of corrosion of the exposed corrosion-susceptible materials in the headspace region 5.

[0064]
Consequently, the present invention provides water storage tanks 100 that exhibit reduced corrosion rates as compared to those not configured as described herein. In some non-limiting embodiments, the water storage tanks 100 exhibit a rate of corrosion in the headspace region 5 that is markedly less than that seen in water storage tanks 100 that do not include the features of the present invention. As such, the present invention can reduce the rate of corrosion by at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90% as compared to water storage tanks 100 that do not include the features of the present invention. As used herein, the rate of corrosion is measured by AST G50-10(2015), Standard Practice for Conducting Atmospheric Corrosion Tests on Metals, ASTM international, West Conshohocken, PA, www.astm.org (retrieved March 26, 2016), the disclosure of which is hereby incorporated in its entirety herein by reference.

[0065] Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.

Claims (21)

THE INVENTION CLAIMED IS

1. A water storage tank comprising:
a tank containing water;
a roof positioned over the tank;
a headspace region formed between the roof and a surface of the water contained in the tank; and a corrosion reduction system comprising: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into the headspace region, wherein the corrosion reduction system reduces a rate of corrosion of the water storage tank.

2. The water storage tank of claim 1, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region in a direction that is non-perpendicular to the water surface.

3. The water storage tank of claim 1, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region substantially laterally across an interior surface of the roof.

4. The water storage tank of claim 1, wherein the device of the active air ventilation system comprises air vent openings that fluidly connect the air exterior of the water storage tank to the headspace region.

5. The water storage tank of claim 4, wherein the device of the active air ventilation system comprises at least one screen that is positioned over at least one of the air vent openings.

6. The water storage tank of claim 1, wherein the active air ventilation system further comprises an air-moving device that facilitates an exchange of air between an interior and exterior of the water storage tank.

7. The water storage tank of claim 1, wherein the active air ventilation system comprises a deflector that directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

8. The water storage tank of claim 6, wherein the active air ventilation system comprises a deflector that is in fluid communication with the air-moving device, and wherein the deflector directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

9. The water storage tank of claim 1, further comprising a mixing device configured to bring cooler water to a top portion of the tank.

10. The water storage tank of claim 1, wherein at least a portion of the water storage tank and/or at least a portion of an interior of the roof is formed from a material that is prone to corrosion.

11. The water storage tank of claim 10, wherein the material that is prone to corrosion comprises a metal.

12. The water storage tank of claim 1, wherein the corrosion reduction system reduces the rate of corrosion of the water storage tank by at least about 10%
to at least about 90%
as measured by ASTM G50-10(2015).

13. A method of reducing a rate of corrosion of a water storage tank comprising actively exchanging air outside of the water storage tank with air inside the water storage tank with a corrosion reduction system to reduce the rate of corrosion of the water storage tank, wherein the corrosion reduction system comprises: (i) a port that enables air to flow out of the water storage tank; and (ii) an active air ventilation system comprising at least one device configured to facilitate movement of air exterior of the water storage tank into a headspace region formed between a roof positioned over the water storage tank and a surface of water contained in the tank.

14. The method of claim 13, wherein the corrosion reduction system is retrofitted into the water storage tank.

15. The method of claim 13, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region in a direction that is non-perpendicular to the water surface.

16. The method of claim 13, wherein the device of the active air ventilation system is configured to facilitate the movement of air exterior of the water storage tank into the headspace region substantially laterally across an interior surface of the roof.

17. The method of claim 13, wherein the active air ventilation system further comprises an air-moving device that facilitates an exchange of air between an interior and exterior of the water storage tank.

18. The method of claim 17, wherein the active air ventilation system comprises a deflector that is in fluid communication with the air-moving device, and wherein the deflector directs air exterior of the water storage tank into the headspace region in a direction that is: (i) non-perpendicular to the water surface; or (ii) substantially laterally across an interior surface of the roof.

19. The method of claim 13, wherein the water storage tank comprises a mixing device, and wherein the method further comprises actively mixing with the mixing device such that cooler water is brought to a top of the water storage tank.

20. The method of claim 13, wherein the corrosion reduction system reduces air temperature, humidity, and levels of oxidizing vapors in the headspace region of the tank.

21. The method of claim 13, wherein the method reduces the rate of corrosion of the water storage tank by at least about 10% to at least about 90% as measured by ASTM G50-10(2015).