Patent Application
20170203917
The embodiments herein relate generally to systems and methods for safely transporting granular material, and, more specifically, to improved systems and methods for safely transporting granular agricultural and industrial materials such as cement, barite, and sand for use in hydrocarbon fracking operations.
Working with certain types of granular material can pose significant health risks. According to the U.S. Occupational Safety & Health Administration (“OSHA”), inhalation of small crystalline silica particles puts workers at risk for silicosis, lung cancer, chronic obstructive pulmonary disease, as well as liver, heart, and kidney disease. With the increase of hydraulic fracturing (“fracking”) over the past 5-10 years, the instances of sicknesses and deaths due to silica inhalation have rapidly increased. Many fracking sites fail to meet current OSHA standards. Moreover, OSHA has proposed a new rule lowering the permissible exposure limit of respirable crystalline silica per cubic meter of air. This lower limit will impact almost any industry that involves transporting or otherwise using silica.
Fracking is a process for stimulating an oil well by fracturing underground rock using a pressurized liquid. The pressurized liquid consists primarily of water mixed with a proppant. A typical proppant is sand, such as “frac sand,” although other granular materials can be used as well. The proppant functions to maintain an induced hydraulic fracture open such that the desired oil or gas can be extracted. A single fracking well can require several thousand tons of frac sand.
Frac sand is mined and processed in a plant to improve its performance characteristics. The sand then gets transported from the plant to the fracking site. This transportation process can involve trains, ships, trucks, conveyors, and other transportation methods. Pneumatic pipe systems and conveyors are routinely used to transport sand from one container to another—for example, from a rail car to a truck or from a truck to a storage facility. Pneumatic and conveyor transfers allow silica particles to permeate the air in the surrounding area, causing a potential health hazard to any workers nearby.
In addition to the health hazards, the typical processes for transporting frac sand have additional drawbacks. For example, a container (e.g., a rail car or a truck) designed to hold frac sand may not be useful for carrying other items. That is, once the load of frac sand has been deposited, the rail car or container cannot be used for another purpose; instead, it must be returned to a location where it can be refilled with frac sand. The lack of reusability increases transportation costs and, as a result, the overall cost of fracking.
Therefore, a need exists for systems and methods for safely and efficiently transporting granular material. More specifically, a need exists for systems and methods for transporting granular material in a manner that limits respirable silica emissions, eliminates harmful pneumatic transfers, and provides lower transport costs.
Embodiments described herein include systems and methods for safely and efficiently transporting granular material. In one embodiment, a method includes providing an expandable container in an unexpanded state, expanding the expandable container from the unexpanded state to an expanded state, and depositing granular material within the expandable container via an input valve. In this embodiment, the expandable container includes at least a top plate, a bottom plate, an outer material coupled to the top and bottom plates, an input valve associated with the top plate, and a discharge valve associated with the bottom plate. The expandable container can also include a containment bladder for holding of the granular material within the container and protecting it from the elements, and a discharge bladder for assisting in discharging the granular material from the container.
In another embodiment, the method also includes transporting the expandable container. The method can further include discharging granular material from the expanded container via the discharge valve. The discharge bladder may be inflated in a manner that urges or biases the granular material within the containment bladder toward the discharge valve. Discharging the granular material may cause the expandable container to return to its unexpanded state. Once in its unexpanded state, the expandable container may be stacked on top of a similar expandable container, also in an unexpanded state, for transporting. This can, for example, require half or fewer train cars to return the expandable containers than is needed for transporting the full containers.
In one embodiment, the expandable container includes a restraint device removably coupled to the top and bottom plates and/or support members associated with the top and bottom plates. Expanding the expandable container may include the step of removing the restraint device.
In yet another embodiment, an expandable container is provided for safely transporting granular material. The expandable container can include a top plate, a bottom plate, an outer material coupled to the top and bottom plates, an input valve associated with the top plate, and a discharge valve associated with the bottom plate. Furthermore, the expandable container can be expanded by applying opposing forces to the top and bottom plates, respectively.
The expandable container may include a containment bladder coupled to the top and bottom plates. The outer material may include at least one Kevlar or Kevlar-reinforced band, and/or may be coupled to the top and bottom plates via retaining rings. The input valve and/or discharge valve may include a spring-loaded plate. A discharge bladder may be included, and can be positioned outside the containment bladder and inside the outer material. The discharge bladder can be configured to be inflated via an inflation port. Once inflated, the discharge bladder can provide a shape that biases the granular material within the containment bladder toward the discharge valve.
The expandable container can also include a restraint device that can be removably coupled to the top and bottom plates, thereby limiting the vertical expansion of the container. The top and/or bottom plates of the expandable container can also include reinforcement members. These reinforcement members can be coupled to the input and/or discharge valves, respectively.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to restrict the scope of the invention as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate various embodiments and aspects of the present invention. In the drawings:
Reference will now be made in detail to the present exemplary embodiments, including examples illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The expandable containers described herein may be used to store and transport granular material, such as frac sand. In one example embodiment, the expandable container may have a containment volume of about 500 cubic feet. In that example the expandable container may be about 10 feet tall in its expanded state and have a diameter of about 8 feet. The height and diameter, and therefore the containment volume, of the container may be varied according to the particular transportation needs of a project. For example, the container may have an expanded height of between 6-14 feet, and may have a diameter of between 4-12 feet. Other sized may be used as well, and these examples are not intended to limit this disclosure in any way.
The outer material 130 can be constructed from a robust yet flexible material such as, for example, Kevlar or other material having similarly high elastic modulus and/or tensile strength measurements. For example, the outer material 130 can be made from a fabric having an elastic modulus of between about 100 and 200 GPa. In some examples, the outer material 130 can be made from a material having a tensile strength of between about 2000 and 4000 MPa. In other examples, material having characteristics outside of these ranges can be used. However, a material with these characteristics can prevent bulging and thereby maintain the uniform cross-sectional diameter of the container as the outer material. The outer material 130 functions to contain the contents of the expandable container 100, including any internal bladders or containment vessels. The outer fabric material 130 can be stronger than steel, on a per-weight basis. However, it also provides flexibility such that the expandable container 100 can be expanded or contracted in an efficient and reliable manner. At the same time, however, the outer material 130 is strong enough to resist tearing or rupturing during use, which may involve heavy machinery and large forces or loads.
For increased strength and overall robustness of the container, support members 160 may be coupled to the top plate 110 and/or bottom plate 120. The support members 160 provide increased rigidity of the top and bottom plates 110, 120, and enable multiple expandable containers 100 to be stacked on top of one another. The support members 160 also provide a mechanism to manipulate the expandable container 100 itself. For example, the loading process may require the top plate 110 to be lifted and/or vibrated to efficiently fill the containment volume with granular material. In this scenario the top plate 110 can be gripped via support members 160 and manipulated as needed. The container 100 can be filled with sand while lifted, allowing the weight of the sand to expand the container 100 downward. Then the full container 100 can 100 can be placed on a train car or other transport.
Additionally, support members 160 can be used to temporarily fix the height of the expandable container 100. As discussed further with respect to
With respect to
A valve plate 210 can be used to control the flow of material into or out of a valve. The valve plate 210 can be provided as a circular disk with a hole that accommodates valve shaft 220, such that the valve plate 210 can slidably move along the valve shaft 220. A biasing mechanism, such as a spring 240, can be used along at least a portion of the valve shaft 220. Spring 240 biases the valve plate 210 in a manner that will cause the valve plate 210 to sit flush with the top plate 110 in its resting position (i.e., when no external forces are being applied to the valve plate 210). A valve pin 230 can be provided along the valve shaft 220 to abut one end of the spring 240, while the other end of the spring 240 abuts the valve plate 210.
To operate the input valve 140, the valve plate 210 is depressed such that it moves along the valve shaft 220 toward the valve pin 230, compressing the spring 240. In practice, the valve plate 210 can be depressed by a loading apparatus. For example, the nozzle of a hopper, tube, or pipe carrying granular material can be shaped to contact and depress the valve plate 210. In some embodiments one mechanism is used to depress the valve plate 210 while a separate component provides the granular material. Any device that depresses the valve plate 210 toward the valve pin 230 can be used to open the input valve 140.
As mentioned above, a discharge valve may incorporate the same, or similar, components described in
Discharge bladder 340 can be inflated during the discharge process when the granular material 350 begins to run low. One purpose of the discharge bladder 340 is to prevent granular material 350 from remaining trapped inside the containment bladder 330 due to the flat-bottomed shape of the expandable container 100. Discharge bladder 340 fills in the areas that may trap the granular material 350, thereby urging the remaining granular material 350 to exit the discharge valve 320.
Discharge bladder 340 may inflate automatically, for example by using input from a sensor that determines the amount of granular material 350 remaining in the expandable container 100. In this embodiment discharge bladder 340 may be connected to a built-in pump provided within, or attached to, the expandable container 100. In other embodiments the discharge bladder 340 can be inflated manually by attaching an air hose to the discharge bladder valve 170.
The unexpanded state of
To prepare the expandable container 100 of
If a restraint device is installed such that the container is prevented from expanding, the restraint device is removed at step 520.
At step 530, the expandable container is expanded. This may involve, for example, lifting the expandable container using the top plate, or support members attached to the top plate, and allowing the container to expand via the weight of the bottom plate. This step may also involve some amount of vibration or movement to encourage the container to expand sufficiently.
At step 540, granular material is deposited into the expandable container via an input valve. This step may occur simultaneously with step 530, or may occur after step 530. For example, when the expandable container is lifted from the top plate, pouring sand into the lifted container can provide enough weight to cause the bottom of the container to expand downward. Step 540 includes accessing the input valve by depressing the valve plate, as described with respect to
Step 540 may also include vibrating or otherwise applying force to the expandable container as the granular material is deposited. The application of force spreads the granular material within the expandable container and allows for an uninterrupted flow of material into the container.
At step 550, the filled expandable container is transported to its destination. Because a filled container can be quite heavy, machinery may be used to lift the filled container and place it on a truck, ship, train car, or other transportation device. In some embodiments, the same machinery is used to expand the container at step 530 and load the container at step 550. In other embodiments separate machines are used at each step.
At step 560, the granular material is discharged from the expandable container at its desired location. Depending on the type of transport vehicle used, the filled containers may need to be removed from the transport vehicle before the granular material is discharged. To discharge the material, the container is positioned in the desired location and the valve plate of the discharge valve is depressed, as shown in
Step 570 includes inflating the discharge bladder (or bladders, if the container is equipped with more than one) such that any remaining granular material is expelled through the discharge valve. As described with respect to
At step 580, the now-empty expandable container is provided in an unexpanded state due to its lack of contents. At this step the restraint device may be installed, or reinstalled, such that it connects to at least one support member along the top plate and one support member along the bottom plate. Once secured, the restraint device maintains the unexpanded geometry of the container. This allows for multiple unexpanded containers to be stacked on top of one another—for example, on a truck or other shipping vehicle. Once the unexpanded containers are returned to the storage location for the granular material, they may be filled again starting with Step 510.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
