Patent Description:
Water collection systems are typically used to provide water to end users such as manufacturing plants, cities, irrigation systems, and power generation facilities located adjacent a body of water such as a river, lake, or salt water bodies. The end users can employ this type of system as an alternative to drilling water well or buying water from a municipality. Many of these systems are also made necessary based on the location of the end user, for example remote locations where water from a municipal source and/or electrical power to operate pumps is not readily available. These water collection systems have the ability to adapt to varying conditions and deliver water efficiently and economically.

Typically, these water collection systems use an inlet pipe adapted to transport water from a position submerged in the body of water to the end user at a location adjacent the body of water. An inlet pipe is submerged in the body of water and the end of the inlet pipe is typically coupled to an intake screen. The intake screen functions as a rough filter, for example, using such as ribs, wire mesh, or perforated screens disposed on an outer surface to prevent the introduction of large waterborne debris and/or aquatic life of a certain size, from entering the inlet pipe.

During normal operation, the intake screen can become plugged and/or blinded so as to negatively impact intake performance. For example, the intake screen can become entrained with debris such as, for example, sticks or logs ore even trash. When the intake screen is used in cold weather climates, temperatures can be low enough to form frazil ice, which can similarly coat or plug the intake screen. If the intake screen is not cleared of this debris, water flow through the intake screen can eventually be halted.

A variety of cleaning systems have been utilized to remove debris including physical scraping devices. While these scraping devices can be effective, the inherent problems associated with maintenance and repair of these submerged scraping devices can make them expensive to operate and lead to significant downtime of the inlet pipe.

An alternative design known as a Hydroburst™ system available from the Johnson Screens® division of the Aqseptence Corporation uses one or more pulses of pressurized air delivered to the interior of the intake screen to expel debris from the exterior of the intake screen. While these air burst systems are very effective, their performance can be hindered as filtering locations move further off shore and away from a supply of pressurized air. In order to have the greatest cleaning success, the submerged supply piping that provides the pressurized air to the interior of the intake screen must be cleared of water prior to pulsing the pressurized air. As the location of the intake screen moves further offshore, the total volume of water that must be cleared from the submerged supply piping continues to increase, which can limit the volume of pressurized air available for the pulses as well as increasing air pressure recharging times between pulses.

As such, it would be advantageous to improve upon current air burst systems for cleaning screen intakes such that debris removal performance can be maintained as filtering locations move further offshore and way from onshore air supplies.

<CIT> describes a method of backwashing a membrane filtration system comprising at least one permeable membrane, the method comprising the step of applying a pressurized gas at a variable pressure to permeate the remaining present in the system when filtration process is stopped or suspended to provide liquid for backwashing pores of the permeable membrane during a backwashing process.

<CIT> describes a screen intake apparatus for a water intake system which uses a cleaning system to clean one or more screen intakes.

<CIT> describes a self-cleaning, back-washable filter apparatus and method for use with a pumping apparatus which is lowered into a well casing.

<CIT> describes a method and apparatus for a backwash system for cleaning an underwater tank coupled on one end to a source of compressed fluid and on the other end to the intake screen assembly.

<CIT> describes a fish screen device which is adapted to be lowered to the bottom of a body of water such as a lake, river or the like and to be raised therefrom.

Representative embodiments of the present invention are directed to systems and methods for purging air burst supply piping of accumulated water prior to delivering pulses of pressurized air to an interior of a screen intake through the air burst supply piping. Generally, the present invention is directed to the removal of accumulated water in the air burst supply piping prior to delivering one or more pulses of pressurized air to the screen intake through the air burst supply piping. In one representative embodiment, the systems and methods of the present invention can include a purge compressor delivering a purging air supply at a head pressure slightly above a head pressure of water in the air burst supply piping, wherein the head pressure of the water is equivalent to a depth at which the intake screen. In another representative embodiment, the systems and methods can include a purge line arranged in a parallel orientation to an air burst supply line, wherein both the purge line and the air burst supply line are operably coupled to a pressurized air tank.

As used throughout the present application, the term "onshore" refers not only to its conventional usage of situated or occurring on land but will also refer to other locations in which screen intakes and their accompanying systems and methods are utilized. These can include both temporary and permanent installations making use of floating barges, either docked, anchored or otherwise free-floating, as well as offshore structures such as oil and natural gas rigs.

Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which:.

While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

As shown in <FIG>, a conventional air burst system <NUM> according to the prior art generally includes an onshore air system <NUM>, a distributor system <NUM> and a submerged screen intake <NUM>. Typically, onshore air system <NUM> will include a receiver tank <NUM> for storing compressed air and a burst compressor <NUM> that charges/fills the receiver tank <NUM> with the compressed air. Generally, the burst compressor <NUM> and receiver tank <NUM> are selected such that the compressed air within the receiver tank <NUM> is pressurized to within the range of <NUM>-<NUM> PSIA. Onshore air system <NUM> can also include a control panel <NUM> that allows an onshore operator to set a burst frequency for the onshore air system <NUM>. The control panel <NUM> can include necessary components for setting the burst frequency including, for example, a digital or mechanical timer, a microprocessor based controller, a programmable logic controller or similar control element and can include an input device such as for example, a keyboard, mouse, display, touch screen display and the like. Distributor system <NUM> generally comprises a length of air supply piping <NUM> having an onshore end <NUM> that is operably connected to the receiver tank <NUM> and an offshore end <NUM> that operably connected to an airburst manifold <NUM> that is located within the submerged screen intake <NUM>.

Typically, an operator will specify a burst frequency of the onshore air system <NUM> using the control panel <NUM>. The burst frequency can vary based on factor including, for example, the water quality in which the submerged screen intake <NUM> resides, the amount of solid contaminants, particles and objects within the water and time of year, for example summer versus winter when frazil ice may be present. Generally, the control panel <NUM> opens a supply valve <NUM> that releases pressurized air from the receiver tank <NUM> into the air supply piping <NUM>. Due to the submerged location of the air supply piping <NUM>, the pressurized air must push any accumulated water out of the air supply piping <NUM> prior to releasing a pressurized burst through the airburst manifold <NUM>. As such, the receiver tank <NUM> must be sized not only to provide the necessary pressurized burst but also to force any accumulated water from the air supply piping <NUM>. This increases the required size and volume of the receiver tank <NUM>, which will consequently increase costs for the air burst system <NUM> and possible make the air burst system <NUM> impractical for use in remote locations.

Referring now to <FIG>, an improved air burst system <NUM> according to an embodiment of the present invention is illustrated. Generally, air burst system <NUM> can comprise an onshore air system <NUM>, a distributor system <NUM> and a submerged screen intake <NUM>.

Onshore air system <NUM> generally comprises a receiver tank <NUM>, a primary compressor <NUM>, a secondary compressor <NUM> and a control panel <NUM>. Primary compressor <NUM> generally compresses air and fills receiver tank <NUM> for use in providing a pressurized burst of air to the distributor system <NUM> through a burst line <NUM>. Secondary compressor <NUM> can be connected directly to the distributor system <NUM> through a purge line <NUM>. Generally, the primary compressor <NUM> and receiver tank <NUM> are selected such that the compressed air within the receiver tank <NUM> is pressurized to within the range of <NUM>-<NUM> PSIA. The secondary compressor <NUM> is generally sized for the removal of accumulated water from the distributor system <NUM> and will be dependent upon the depth at which the distributor system <NUM> and submerged screen intake <NUM> are submerged. For example, the second compressor <NUM> can be sized so as to provide compressed air at greater than <NUM>-<NUM> feet of head pressure. Onshore air system <NUM> can also include a controller <NUM> in the control panel <NUM> that allows an onshore operator to set a burst frequency for the onshore air system <NUM>. The controller <NUM> can include necessary components for setting the burst frequency including, for example, a digital or mechanical timer, a microprocessor based controller, a programmable logic controller or similar control element and can include an input device such as for example, a keyboard, mouse, display, touch screen display and the like. Controller <NUM> will selectively open and close a purge valve <NUM> and a burst valve <NUM>, located within the purge line <NUM> and burst line <NUM> respectively, so as to selectively provide purge air or burst air to the distributor system <NUM>.

Distributor system <NUM> generally comprises a length of air supply piping <NUM>. The air supply piping <NUM> generally includes an onshore end <NUM> that is fluidly coupled to both the burst line <NUM> and the purge line <NUM>. The air supply piping <NUM> further comprises an offshore end <NUM> that is operably coupled to an airburst manifold <NUM> that is located within the submerged screen intake <NUM>. The air supply piping <NUM> can further comprise a supply bend <NUM> located between the onshore end <NUM> and the offshore end <NUM> to help ensure that the air supply piping <NUM> is cleared of water prior to supplying burst air to the airburst manifold <NUM>. Air supply piping <NUM> can further comprise a pressure senor <NUM> proximate the offshore end <NUM>, wherein the pressure sensor <NUM> can supply pressure data to the control panel <NUM> indicating when a pressure reading in the air supply piping <NUM> is equal to the pressure of the purging air supplied by the second compressor <NUM> such that confirmation is provided that any water in the air supply piping <NUM> has been removed and the air burst can be provided from the receiver tank <NUM>. In some embodiments, air supply piping <NUM> can further comprise a screen valve <NUM> located in proximity to the offshore end <NUM>, wherein the screen valve <NUM> can be selectively opened and closed at the direction of the control panel <NUM>. Screen valve <NUM> can allow air supply piping <NUM> to be fully pressurized throughout its length, for example, between the onshore air system <NUM> and the offshore end <NUM>. As illustrated, screen valve <NUM> can be external to the submerged screen intake <NUM> or alternatively, screen valve <NUM> can be in proximity to the airburst manifold <NUM> that is located within the submerged screen intake <NUM>.

In operation, an operator will specify a burst frequency of the onshore air system <NUM> using the control panel <NUM>. The burst frequency will vary based on the factors previously discussed with respect to air burst system <NUM> and can include, for example, water quality including the presence of solid contaminants, particles and objects within the water and time of year, for example summer versus winter when frazil ice may be present. In contrast to the prior art, the air burst system <NUM> of the present invention undergoes a purge cycle prior to providing pressurized air from the receiver tank <NUM>.

During the purge cycle, the control panel <NUM> causes the purge valve <NUM> to be opened such that the secondary compressor <NUM> can supply purge air through the purge line <NUM> and into the air supply piping <NUM>. As mentioned previously, the pressure at which the secondary compressor <NUM> operates is dependent upon the submerged depth of the air supply piping <NUM> and the submerged screen intake <NUM>. For example, the head pressure of the purge air will typically be greater than <NUM>-<NUM> feet of head and in all cases should exceed the submerged depth of the air supply piping <NUM> and the submerged screen intake <NUM>, any accumulated water within the air supply piping <NUM> and submerged screen intake <NUM> is expelled through the airburst manifold <NUM> such little to no water remains within the air supply piping <NUM> and the submerged screen intake <NUM>. With the water evacuated from the air supply piping <NUM> and the submerged screen intake <NUM>, the pressure sensor <NUM> transmits a signal to the control panel <NUM> indicating that the pressure within the air supply piping <NUM> exceeds the depth pressure so as to provide the control panel <NUM> with confirmation that the purge cycle has been completed. Either prior to or during the purge cycle, primary compressor <NUM> can be operating independently as directed by the control panel <NUM> to fill the receiver tank <NUM> with pressurized air at a desired air burst pressure. In the event that the air supply piping <NUM> includes the screen valve <NUM>, screen valve <NUM> can be closed following completion of the purge cycle to maintain the pressurized purge air within the air supply piping <NUM> until an air burst is requested.

Following the completion of the purge cycle, the control panel <NUM> closes the purge valve <NUM> and causes the burst valve <NUM> to open. With the burst valve <NUM> open, burst air from the receiver tank <NUM> is supplied into now evacuated distributor system <NUM>. The burst air supplied from receiver tank <NUM> is provided at a pressure of <NUM>-<NUM> PSIA. As no water is present within the air supply piping <NUM> and the submerged screen intake <NUM>, the volume of burst air necessary to achieve a pressurized burst through the airburst manifold <NUM> is significantly reduced as compared to the prior art and may constitute less than half of the air volume necessary with the prior art. As such, the capacity of both receiver tank <NUM> and primary compressor <NUM> can both be significantly reduced in comparison to conventional designs resulting in significant savings and making the air burst system <NUM> practical in some remote locations that otherwise may be impractical. For example, the design capacity of receiver tank <NUM> can shrink by <NUM>% or more, for example, from about <NUM>,<NUM> gallons to about <NUM>,<NUM> gallons or less leading to significant savings in both construction and transportation. In addition, the reduced size of the primary compressor <NUM> as compared to conventional designs can allow for the air burst system <NUM> to utilize solar power making the air burst system <NUM> even more advantageous for remote locations. Furthermore, the evacuation of water from the distributor system <NUM> during the purge cycle can allow for the offshore distance of the submerged screen intake <NUM> to be increased, for example, from a current maximum of about <NUM>,<NUM> feet offshore to an extended distance of <NUM>-<NUM> offshore. Finally, the purge cycle allows for the diameter of the air supply piping <NUM> to be decreased which can lead to significant cost savings, especially when the submerged screen intake <NUM> is located a significant distance offshore.

Referring now to <FIG>, an alternative embodiment of air burst system <NUM> can include the addition of a secondary tank <NUM> that is filled by the secondary compressor <NUM> and which is directly connected to the purge line <NUM>. Operation is otherwise similar to air burst system <NUM> but with the exception that the purge air comes from the secondary tank <NUM> as opposed to directly from the secondary compressor <NUM>. This can allow the secondary compressor <NUM> to be reduced in size/capacity as the secondary compressor <NUM> can fill the secondary tank <NUM> over an extended time as opposed to being sized to purge all of the air supply piping <NUM> directly. In addition, secondary tank <NUM> is not required to be fabricated to withstand the high pressures of the receiver tank <NUM> and the corresponding air burst pressures such that the costs of fabricating the secondary tank <NUM> can be reduced.

Referring now to <FIG>, an alternative embodiment of an air burst system <NUM> can similarly make use of a purge cycle prior to providing pressurized air to the submerged screen intake <NUM>. The performance and advantages of air burst system <NUM> can be substantially the same as air burst system <NUM> but using a different configuration. In air burst system <NUM>, secondary compressor <NUM> is essentially by directly connecting the purge line <NUM> to a pressure regulating valve <NUM> that is fluidly connected to the receiver tank <NUM>. As directed by the control panel <NUM>, the pressure regulating valve <NUM> bleeds the high pressure air contained within the receiver tank <NUM> to the desired purge pressure where it is directed into the distributor system <NUM>. As such, pressure regulating valve <NUM> can further perform the function of purge valve <NUM>. Following the purge cycle, the control panel <NUM> closes the pressure regulating valve <NUM>, whereby the burst valve <NUM> is opened and the burst air is provided from the receiver tank <NUM> in a manner similar to that as described with respect to air burst system <NUM>.

With respect to air burst system <NUM> and air burst system <NUM> as previously discussed, a means for purging a distributor system will generally comprise the components described relative to the purge line <NUM>. For example, the means for purging a distributor system relative to air burst system <NUM> will generally comprise the secondary compressor <NUM>, the purge line <NUM>, the purge valve <NUM> and the operational control provided by the control panel <NUM>. Relative to air burst system <NUM>, the means for purging the distributor system can comprise the receiver tank <NUM>, the purge line <NUM>, the purge valve <NUM>, the pressure regulating valve <NUM> and the operational control provided by the control panel <NUM>.

Claim 1:
An air burst system for cleaning submerged screen intakes, comprising:
an onshore air system (<NUM>);
a submerged screen intake (<NUM>); and
a length of air supply piping (<NUM>) fluidly connecting the onshore air system and the submerged screen intake, said length of air supply piping including a pressure sensor (<NUM>) for monitoring pressure within the length of air supply piping,
wherein the onshore air system includes a burst line (<NUM>) for introducing one or more pulses of pressurized air to the length of air supply piping for cleaning debris from the submerged screen intake and a purge line (<NUM>) for introducing purge air to the length of air supply piping for purging water from the length of air supply piping, the purge line being fluidly connected to the submerged screen intake, ,
wherein the onshore air system is configured to receive pressure data from the pressure sensor indicating that a pressure reading in the length of air supply piping exceeds a maximum depth pressure of the length of air supply piping and, in response to this indication, commencing delivery of one or more pulses of pressurized air to the length of air supply piping.