ES3004307T3 - Suction device for the removal of muddy and/or viscous sediment stratified on the bottom of a storage tank bottom - Google Patents

Abstract

This is a suction device (1) for removing stratified muddy and/or viscous sediment from the bottom of storage tanks. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Suction device for removing stratified muddy and/or viscous sediments from the bottom of storage tanks

The object of the present invention is a suction device for the removal of stratified muddy and/or viscous sediments at the bottom of storage tanks.

State of the art

In large industrial plants, petroleum product storage tanks are often found, usually above ground, with vertical cylindrical walls. These tanks are sometimes very large, up to 100 meters in diameter, and usually have a flat or slightly sloped bottom, made of carbon steel with a painted surface or a fiberglass or similar lining.

Over time, a heavy, muddy, bituminous sediment forms inside the tank, so viscous that it cannot be pumped or removed using the systems designed for normal process flow. For this reason, it is necessary to periodically shut down the tank to empty the liquid phase to remove this sediment and restart the normal storage process. These activities typically require the entry of personnel and machinery from the side of the cylindrical mantle through cylindrical doors with an internal diameter of approximately 600 mm; in fact, this size is the standard required by the market for this type of equipment.

There is also a need for this technology not only in hydrocarbon storage tanks, but in many other closed or open flat-bottom tank situations where there are problems with toxicity, explosiveness, chemical or biological hazards, or radioactivity.

The tanks inside are confined spaces classified as ATEX zone 0 with risk of explosion, so the use of no-entry solutions with appropriate ATEX marking is mandatory for sediment removal and subsequent cleaning activities.

Currently, sediment is removed using pneumatic suction conveying systems generated by self-expelling vacuum pumps, or by volumetric transfer pumps placed outside near the tank inlet doors.

Commercially available remote-controlled robots operate connected by a flexible suction hose to self-expelling blowers, placed far from the tank because they are not ATEX certified and therefore cannot enter environments, such as tanks, that pose a risk of explosion.

Positive displacement pumps are sometimes used outside the tanks, as they are not classified as ATEX Zone 0. Their suction line is moved manually inside the tanks. This solution, not only from a technical perspective, but also from a limited operating radius, is also often challenged by people inside the tanks.

The practice of using mechanical transport systems, such as skid steer loaders or other manual loading systems, is much less common today due to the risk to human personnel.

From a technical standpoint, the manual solution using mechanical earthmoving vehicles (converted to adapt to the different conditions found inside the tanks in terms of size and gas emissions) would be the most efficient, since the sediment, with a consistency very similar to a very dense, pasty solution, is separated from the mass and loaded onto mini-loaders for transport to the outside. However, it is not productive due to the considerable size of the bottom, which requires long times to repeatedly transport small fractional quantities to the outside. It is also only conceivable for situations where there is free access from the outside (and not restricted by the limited inlet passage), there is no danger of explosion, and the atmosphere is breathable.

Unlike the solution described above, there is an alternative solution that uses vacuum, with a maximum limit of 0.9 bar, to transport the sludge through a long flexible rubber hose (which can be extended up to 50-75 meters depending on capacity) until it self-flushes. However, the productivity of this solution can be very limited because it depends on:

• length and diameter of the suction tube;

• suction air flow generated by self-discharge;

• temperature and viscosity conditions of the sludge.

Any solution on the suction side requires that once the sedimentation tank is full, it must be emptied, and therefore the suction process must be interrupted.

A different possibility is the use of a positive displacement pump (which instead has a maximum limit of 5-6 bar), which has the advantage of continuous operation for as long as the pump can work without stops due to the movement of material out of the tank. This greater efficiency provides a considerable reduction in the time required to empty a tank, but is limited by the fact that the suction port of the suction pipe must be under a constant height.

However, both the solution using depression and the solution using a positive displacement pump have proven to be unsuitable for expelling the sludge sediment directly to the outside, since it is excessively dense and viscous. WO 2015/026019 A1, EP 3048220 Al and CN 200 960 518 Y disclose a suction device according to the preamble of claim 1. EP 0 140778 Al also discloses a suction device for removing stratified muddy and/or viscous sediments at the bottom of a storage tank.

Object of the invention

The object of this invention is to overcome the drawbacks of the prior art.

A main object of the present invention is to provide a system capable of intelligently and continuously transporting the material deposited at the bottom of the tank to the suction port of the pump without having to be inside the tank to be cleaned.

Another objective is to provide a system that makes said material manageable by said pump.

An important object of the present invention is to provide a system that makes the handleable material continuously available at the suction port of the pump.

Another important object of the present invention is to have a system that can operate continuously without stopping to change the external storage tank.

An important object of the present invention is a system that may not be limited by the dimensions of the inlet mouth.

Another object of the present invention is to provide a system that can adapt to the consistency and quantity characteristics of the sediment.

An important object of the present invention is a system that can operate even in the presence of explosive atmospheres.

Another object of the present invention is a system that is not limited by the distance at which bottom sludge removal operations must be carried out.

All the aforementioned objects and others that will become more apparent from the continuation of the description are obtained with this invention, characterized by the features highlighted in the claims.

Explanation of the invention

The invention consists of a suction device for removing stratified muddy and/or viscous sediments at the bottom of a storage tank according to claim 1.

In other words, the present invention allows a tank to be cleaned without operator supervision with all the necessary automatic adjustment devices for transferring bottom sludge mounted on board, and is configured as an automatic system for pretreatment of bottom sludge, mounted on board a self-propelled vehicle that can move within the tank to transfer the sludge to the outside through a cavity pump.

The device of the invention comprises a self-propelled vehicle carrying a cavity pump specifically designed to operate in an environment with a continuous presence of flammable gases and vapors; the device is controlled remotely without the presence of an operator, using an automatic priming system that keeps the pump's suction port supercharged to maximize productivity and allow the pump to operate under specific conditions without dry running or loss of suction. Indeed, proper priming of the pump is essential for it to operate in the absence of cavitation and the resulting mechanical and dynamic vibrations of the flow. The cavity pump has a good priming capacity and can generate a high pumping pressure (5-6 bar), but it is essential that the material be mechanically conveyed until the suction pipe is filled to avoid losing priming and to operate with a full pipe.

To achieve this effect, a system has been provided consisting of at least one arm opened by hydraulic cylinders carrying at least one rotating tool, for example, a rotating vertical auger, to draw the viscous fluid towards the suction mouth.

Typically, crude oil or its derivatives form a sludge that typically has high viscosity and a mechanical consistency similar to a bituminous product, which resists suction or pumping with normal systems. For this sludge (often referred to as SLOP OIL) to be pumped or suctioned through a flexible rubber tubing, it must be mechanically worked with systems that shear and mix it at high speed, bringing it close to a slurry with a viscosity suitable for pumping.

Advantageous features of the invention

Advantageously, said rotating tool has a vertical axis with the suction mouth located near the bottom of the tank to be cleaned, ensuring that the pre-treated sludge, which has acquired a consistency that can now be sucked up, keeps the pump continuously primed.

Advantageously, the mobile arm, moved by a hydraulic cylinder, is articulated with an axis parallel to the axis of rotation of the rotating tool, thus being able to extend the radius of action of said tool and confer an additional action of bringing the pretreated sludge closer to the suction mouth.

Advantageously, said rotating tool can slide in a controlled manner along said movable arm so as to widen or narrow the cross-section of the removal device's attachment depending on the nature, consistency, and quantity of sludge present. Advantageously, at the end of the movable arm, with a profile approximately parallel to the axis of rotation of said arm, there is a cutting/separating/detaching blade for cutting the material to be pretreated from the solid mass of untreated sludge, thereby achieving the appropriate amount of material to be treated by the rotating tool, mechanically detaching it from the viscous bond with the rest of the sludge.

Advantageously, said rotary tool is provided with a series of fixed combs, interposed between said rotating discs or with a mobile oscillating blade that detaches from the auger to clean and detach the material that was adhering to it, maintaining the same rotation speed.

Finally, a free-rotating orthogonal cutting system is provided, which separates the material from the auger and forces it towards the pump suction port.

Advantageously, the direction of rotation of the rotating tool is reversible on command, due to the need to detach and/or bring the pre-treated sludge closer to the suction inlet.

The movable arm has a continuous confining wall that extends for at least one of the longitudinal extension of the rotating tool, and is positioned on the side opposite the suction mouth (with respect to the rotating tool), establishing a confined space for continuous and prolonged treatment of the sludge, bringing it to the appropriate consistency.

This confinement wall extends from the moving arm to the bottom of the tank, and ends with a flexible rubber/plastic scraper profile that scrapes along the bottom of the tank to bring the pretreated material closer to the suction inlet.

Advantageously, said movable arms, during their movement, open in a position at a certain distance from the suction mouth, and counteract the overturning moments that may occur due to operation and/or disconnected or irregular bottom, acting as stabilizers, resting with their ends facing the bottom and away from the center of gravity of the device, and counteracting said overturning moments.

All the advantages mentioned and others that will appear in the following description are illustrated more clearly with reference to the drawings and to an exemplary and non-limiting embodiment shown below.

Brief description of the drawings

The technical characteristics of the invention, in accordance with the aforementioned objects, are clearly apparent from the content of the claims below, and the relative results will be evident from the detailed description that follows with reference to the drawings, which illustrate a purely exemplary and non-limiting embodiment, in which:

Fig. 1 shows the suction device for removing stratified muddy and/or viscous sediments at the bottom of a storage tank, object of the invention, according to a perspective view from above;

Fig. 2 shows the device of Fig. 1 in a top plan view;

Fig. 3 shows the device of Fig. 1 from a side plan view;

Fig. 4 shows the front of the device in Fig. 1 enlarged;

Fig. 5 shows the front of the device in Fig. 1 enlarged, viewed from a different perspective than that shown in Fig. 4;

Fig. 6 shows the device of the invention according to a front and top perspective view, in which the movable arms stand out in an open configuration and with the rotating tools supported on the free ends of said movable arms extended to their maximum extension;

Fig. 7 shows the same as Fig. 6 with the movable arms slightly rotated towards a closed position;

Fig. 8 shows the same as Fig. 6 with the movable arms retracted to the minimum extension, bringing the movable tools closer to the suction mouth;

Fig. 9 shows what is shown in Fig. 6 with the movable arms fully rotated to the closed configuration, in which the movable tools are placed close to each other in a juxtaposed manner;

Fig. 10 shows what is shown in Fig. 6, but equipped with a rotating tool having screw-type cutting edges, with respect to what is shown in Figs. 6 to 9, where the rotating tool has cutting edges configured as rotating discs.

Detailed description of a preferred exemplary embodiment. The drawings show a double-faced rotary auger system with metal cutting edges that demolish the compacted sediment face, pushing the material toward the double suction face corresponding to the two suction ports of the pump.

The system shown has mechanical protections certified to operate in the presence of an explosive atmosphere, and has two degrees of freedom to maximize the working front under all conditions:

• Horizontal opening of the two arms (right and left) to work on a surface wider than the width of the machine; the working width is adjustable by horizontally shifting the working axis of the rotating auger relative to the arm's rotation axis. The closing movement of the arm itself induces an additional pushing effect of the muddy material toward the two suction pipes;

• Clockwise and counterclockwise rotation of the two vertical augers, the speed of which is automatically controlled by the pumping fluid's maximum pressure adjustment system. One direction of rotation represents the normal working direction of the augers, which mix and transport the material toward the suction pipe; the opposite direction of rotation is used to free the mechanism of any foreign bodies that could impede the free rotation or closure of the two arms.

With reference to the drawings, the suction device 1 comprises a cleaning device 2 supported by mobile devices 3 consisting of a self-propelled tracked vehicle. The suction device must have a sufficiently compact cross-section so that it can pass through the inspection opening in the side walls of the large tanks whose bottom the suction device is to clean.

In fact, the bottom of such tanks requires periodic cleaning, which consists of mechanically removing the viscous sludge to the outside of the tank by means of the device of the invention, designed to operate in areas with risk of explosion and controlled remotely.

The cleaning device 2 comprises a volumetric pump 4 with two suction mouths 5 facing the bottom and located close to it.

In fact, it is very important that the positive displacement pump 4 always operates at full capacity, avoiding idling, which could cause cavitation and overheating, situations that must always be avoided in areas at risk of explosion. Therefore, the position of the suction port close to the ground provides the best priming, combined with the other features of the invention.

On the side of each suction mouth 5, a movable arm 6 is articulated with a vertical axis that can be moved with a rotary movement by means of an actuator 7 that acts on the arm 6 itself and with an opposite application point on the fixed structure of the cleaning device 2. Advantageously, said actuator 7 is a hydraulic cylinder. Supported and held on each movable arm 6, there is a rotating tool whose peripheral profile is rotated and enters stratified and viscous to obtain a mechanically pretreated sludge such that it has characteristics (viscosity, consistency, stickiness, fluidity) that can feed the cavity volumetric pump 4 and be transported through a conduit with a suitable cross section outside the tank.

Preferably, as shown in the drawings, said rotating tool is a worm gear. The direction of rotation of the rotating tool can be changed to meet the different needs that arise during the execution of the various work phases, one direction being preferable for the processing and treatment of the stratified sediment and the opposite direction for the transport of said pretreated sludge to the suction inlet 5 or to free the screw from a flood.

It is also envisaged that this auger can move along the longitudinal extension of this mobile arm 6 to adapt to the nature and characteristics of the sediment-shaped material to improve productivity.

In fact, the movement of the movable arm 6 with a rotation in the direction of the suction mouth 5 also helps to keep the pump primed and to maintain a quantity of material in the suction pipes to avoid running dry.

If necessary, the rotary tool may adopt the configuration of a series of spaced rotating discs, the circumferential edge of which adheres to and comes into contact with the untreated sediment, fluidizing it and making its characteristics suitable for the corresponding suction. Occasionally, given the nature of the material to be removed, it appears as a combined colloidal aggregate that can only be detached by a partition made by the blade 9 arranged at the free end of the movable arm 6.

Advantageously, this blade 9 with a profile extending from the height of the movable arm towards the lower part approaching it, for a rotary movement of the movable arm, is able to section off the untreated parts of the base to make them available for pretreatment of the rotating tool 8.

Said mobile arm 6 is also equipped with a confinement wall 10 arranged adjacent to the outer profile of the auger on the side opposite to that facing the suction mouth, limiting and collecting the pre-treated material towards the auger and being able to act both as a definition of the space for the continuous and repeated treatment of the same material, and as a tile to move this material towards the suction mouth.

Finally, said confinement wall is provided, on the edge facing the bottom of the tank, with a scraper 11, which is an extension of the confinement wall itself, which scrapes the bottom without damaging it, since it is made of a flexible rubbery/plastic material.

Claims (10)

1. Suction device for removing stratified muddy and/or viscous sediments at the bottom of a storage tank comprising a volumetric pump (4) on board a remote-controlled self-propelled vehicle capable of moving inside a tank without the supervision of an operator, the delivery pipe of said pump pressing the material to be transported out of the tank to be cleaned, and the suction pipe of said pump is continuously fed with material to be removed from a pretreatment system at the base, said pretreatment system being located near the suction mouth (5) of said pump (4) and comprising at least one rotating tool (8), such as a screw, or a series of spaced and coaxial discs, supported by at least one movable arm (6), capable of moving said rotating tool (8) closer to and further away from at least one suction mouth (5) of the suction pipe, characterised in that the movable arm (6) has a continuous confining wall (10) and said confining wall (10) It extends from the movable arm (6) to the tank and ends with a scraper (11) consisting of a flexible rubber/plastic scraper profile that scrapes the bottom of the tank. 2. Suction device according to claim 1, characterized in that said rotating tool (8) has a vertical axis with respect to the suction mouth (5) located near the bottom of the tank to be cleaned. 3. Suction device according to claim 1, characterized in that said movable arm (6) is moved by an actuator (7) and is articulated with an axis parallel to the axis of rotation of the rotating tool (8). 4. Suction device according to claim 1, characterized in that said movable arm (6) constitutes a sliding guide for said rotating tool (8) and can slide in a controlled manner along said movable arm (6). 5. Suction device according to claim 1, characterized in that at the end of the movable arm (6), with a profile approximately parallel to the axis of rotation of said movable arm (6), there is a cutting/separating/detaching blade (9) for sectioning the material to be pretreated with respect to the substantial mass of untreated sludge. 6. Suction device according to claim 1, characterized in that said rotary tool (8) has a series of fixed combs, interposed between said rotary tools or has an oscillating mobile blade that is detached from the worm screw to clean and detach the material adhering to it while maintaining the same rotation speed. 7. Suction device according to claim 1, characterized in that said rotating tool (8) is provided with a freely rotating cutting system that detaches the material from the worm screw and directs it forcibly towards the suction mouth of the pump. 8. Suction device according to claim 1, characterized in that said rotary tool (8) has a reversible rotation direction on command. 9. Suction device according to claim 1, characterized in that the mobile arm (6) has a continuous confinement wall (10) that extends at least along a part of the longitudinal extension of the rotating tool (8) and positioned on the side opposite the suction mouth (5), with respect to the rotating tool (8), defining a confined space for a continuous and prolonged action of treatment of the base of the same, bringing it to the appropriate consistency. 10. Suction device according to claim 1, characterized in that said movable arms (6) during movement open in a position remote from the suction mouth (5) and counteract the overturning moments that may occur due to operation and/or disconnected or irregular bottom, acting as stabilizers, resting with their end facing the bottom and remote from the centroid of the device (1) and counteracting said overturning moments.