WO1995022415A1

WO1995022415A1 - Tank cleaning system

Info

Publication number: WO1995022415A1
Application number: PCT/DK1994/000059
Authority: WO
Inventors: Jan Henning Skaara; Leif Gottlieb
Original assignee: Hydropower Inc., Ltd.
Priority date: 1994-02-16
Filing date: 1994-02-16
Publication date: 1995-08-24
Also published as: AU5998894A

Abstract

During use of tank cleaning devices with dual movement nozzles (18) it is known, and it is also advantageous, to use the cleaning liquid to drive a turbine (22), which drives the cleaning head (12, 18). The driving speed can be adjusted by means of a valve (30) in a by-pass connection (28) outside the turbine. The invention presents a device by means of which this can be done with a minimum loss of pressure and with a low risk of the by-pass valve (30) being blocked by foreign bodies. Furthermore, the driving device is designed in such a way that the driving speed can not only be set but can also quickly be varied by remote control means, whereby the device can be driven with dynamic steering of the nozzle movements during its work cycle.

Description

Tank cleaning system

The present invention relates to a tank cleaning system or device as described in the introductory part of claim 1. The purpose of these devices is to produce such movements of the said flushing head that pressurized jets can be emitted from one or more nozzles on the head, which jets strike the sides of the tank and thus clean them.

It can be necessary to carry out more or less meticulous cleaning of the tank walls depending on how much consecutive cargoes differ in type. This can be allowed for by making changes in the movement characteristics of the spraying head. It is known that the flushing head can be used to rotate a jet nozzle in the horizontal plane, which jet nozzle in turn swings up and down or rotates in the vertical plane during this rotation, whereby the jet from the nozzle will strike the tank walls in a line pattern, which will be denser the more slowly the movements occur.

The most common practice until now has been that the movements of the flushing head have been controlled by separate drive means, e.g. a compressed air or electric motor, whereby it has in any case been possible to regulate these movements independently of the through flow of cleaning fluid. However, these known devices have been relatively expensive and it has been recognized both before and since that it is more practical to drive the movement of the flushing head with the aid of the energy that is represented by the cleaning fluid that is pumped through. Originally, the whole flow of fluid was conducted through the drive turbine in order to move the flushing head, whereby it was impossible to differentiate between the inlet flow and the movement speed of the flushing head. However, it has recently been recognized (see GB-A-2,028,113) that such a differentiation is in fact possible, that is to say by arranging an adjustable by-pass connection outside the turbine.

Thus, for a given flow of cleaning fluid, it can be achieved that the turbine receives a greater or lesser portion of this flow so that the flushing head will move correspondingly quickly or slowly and will thus create a flow pattern that is correspondingly more or less dense. The unique density (cf. the above-mentioned GB-A2-028,113) is based on the fact that the inlet fluid is led in sideways to a chamber in the bottom of which there are two outlet openings positioned immediately adjacent to one another, that is, on the one hand, leading to the turbine and, on the other hand, to the said by-pass conduit. While one may achieve in this way the above-mentioned advantages with regard to the adjustment of the turbine speed, the method of leading in the fluid is extremely unsuitable as, on the one hand, a noticeable fall in pressure will occur at the sharp change of direction from the side introduction to the downflow through the outlet opening, and, on the other hand, very unfavourable flow proportions will occur for the driving of the turbine. This will be explained in more detail as follows:

On tankers the cleaning apparatuses in question are normally arranged in an extensive common supply network. A powerful compressor pump is used to supply the system but it is unavoidable that a certain loss of pressure will occur somewhere in the network, especially if other cleaning apparatuses are also in operation. It very disadvantageous if considerable pressure losses occur immediately before the individual cleaning apparatuses; a pressure loss at these places can manifest itself in an almost exponential effect, such that a considerable reduction in force will occur in the emitted jets of cleaning fluid. A certain pressure loss in the cleaning apparatuses will be inevitable, but this loss will be even greater if a pressure loss has already occurred in the entrance to the apparatuses.

With regard to the operation of the turbine it is important that the fluid be supplied in a steady stream as any turbulence can give rise to serious operational disturbances. In the case of the arrangement according to the above-mentioned GB,A,2,028,113 it will be unavoidable that powerful vortexes occur in the inlet chamber of the turbine, and it should also be noted that the construction in question is not previously known in practice.

The purpose of the invention is to present a cleaning apparatus that is distinguished by high effectivity and great practicality in all other aspects.

The apparatus according to the invention is primarily characterized by those features that are given in the characterizing part of claim 1. Thus, provision is made to enable the fluid to flow to the turbine in a reasonably steady stream and without any particular pressure loss. Similarly, the branching off to the by-pass connection can proceed in an even flow through the side outlet. Another advantage of this arrangement is that any foreign bodies, (e.g. pieces of soldering wire), which appear fairly frequently in the incoming flow of fluid, will be carried directly down to the turbine, which can be constructed to resist the associated effects, while it is thus also achieved that foreign bodies can not easily become stuck in the inlet to the by-pass connection or block the by-pass valve. The above-mentioned known apparatus is vulnerable in this aspect.

In a preferred embodiment the apparatus according to the invention appears as a new concept with the turbine and the gearbox arranged in a surrounding apparatus housing, which acts as the said collecting chamber. The inlet pipe to the turbine leads directly down into the turbine from the top of the housing and outside the side opening in this pipe there is arranged an adjustment valve in the form of an annular body directly on the outside of the pipe. Thus, the cleaning fluid will go from the side opening of the pipe directly out into the collecting chamber and the adjustment valve will be immediately controlled on the pipe. It can be operated by an axial or periferal displacement and it is connected via a transmission to an exterior operating element on the top of the apparatus housing. The gearbox inside this is cooled by the through-flowing fluid.

In this connection it is a particular feature of the invention that a gearbox of dry, sealed and lubricant-free type should preferably be used, whereby the apparatus is well-suited for permanent mounting in tanks for all kinds of cargo including foodstuffs.

Another particular feature of the system according to the invention is that the above-mentioned operating element for the by-pass valve can be connected by means of a remote control device, not only for general setting of the valve but also for continuous variation of the setting during the operational cycle of the apparatus. If the turbine works with a constant speed, the cleaning jet is moved with a constant angular velocity, whereby its point of impact against the wall will move with greater or lesser speed according to the distance between the impact area and the nozzle. Thus, the jet will be less effective at the places that are further away than at the places that are closer and if the "correct" working speed is chosen for the far away places, i.e. is chosen to be relatively slow, the jets will be over-effective and will take a long time at the closer places. During operative variation of the by-pass valve the speed can be increased for cleaning of the closer places to avoid unnecessary over-consumption of cleaning fluid or cycle time.

In connection with the apparatus a cleaning head with dual-rotating nozzle(s) is preferably used, which promotes a steady operation and enables cleaning everywhere, including straight up from the cleaning head.

The invention is described more closely with reference to the figures as follows:

Fig. 1 is a side view of the apparatus according to the invention, and

Fig. 2 is a more detailed cross section of the upper part of the apparatus.

Fig. 1 shows the top 2 of a tank, in which the shown apparatus is fixedly mounted. It includes an apparatus 4 which has, at the top, a connection flange 6 for an inlet pipe 8 for cleaning fluid and, at the bottom, a downward-directed fixed pipe 10 at the bottom of which is carried a flushing head 12. Inside the pipe 10 there is an axle 14, which is driven by a turbine in the housing 4, and which drives the flushing head 12 round, whereby a sprocket wheel at the lower end of the pipe 10 causes a rotation of a horizontal axle 16 in the head 12. This axle carries one or several radially projecting spray-nozzles 18, to which cleaning fluid is led via parts 10, 12 and 16. Such a dual-rotating flushing head is known from other types of apparatus and therefore will not be more closely described here.

At the upper end of the housing 4 there is situated a pipe 20 leading straight downward from the flange 6, which pipe leads down to the above-mentioned turbine 22 from where the supplied fluid flows out into the housing 4 through outlet openings 24. The turbine 22 drives an inlet axle on a gear housing 26 situated in the lower end of the housing 4 and the above- mentioned axle 14 constitutes the exit axle from this gear housing. In the pipe section 20 wall openings 28 are formed at a distance above the turbine 22, which wall openings can be more or less covered outwardly by a surrounding annular flange 30 which can be moved with the aid of a transmission 32 between this part and an upper, automatic or manual operating unit 34 at the top of the housing 4. Thus, it is possible to create a desired opening between the flow of fluid to the turbine 22 and the flow of fluid which will flow through the opening(s) 28 into the housing 4 directly from the pipe 20. The entire flow of fluid will be conveyed to the flushing head 12 without any significant pressure loss, but with the aid of the valve system 28, 30 it can be decided how great a part of the flow is led through the turbine 22, whereby the movement speed of the flushing head 12 can be controlled as desired. This will be able to be controlled dynamically from a computer, as shown at 35.

It should be noted that it would normally be sufficient to conduct a fairly small part of the flow through the turbine, so that the associated pressure loss in no way will be dominant. Similarly, the pressure loss from the pipe 20 through the openings 28 and down to the flushing head 12 will be very small.

In fig. 2 the upper part of the apparatus is shown in detail, while the remaining parts are almost self-explanatory, so that references to these can be kept to a nMnimum. The annular flange 30 has an internal thread to connect it to the pipe 20, and an external toothing 40, which is in engagement with a gear wheel 42 on a projecting spindle 44 connected to the upper operating unit 34. This is shown as the top of the spindle 44, where a hand wheel can be mounted, but it can also be used for connecting it to a remote driving motor.

The blades of the turbine 22 are surrounded by an outer race 46, which contributes to a high efficiency. Stationary vanes 48 are placed immediately above the turbine.

The turbine axle 50 moves an upper gear wheel 52 in the gearbox 26 and, through several transmissions, moves a lower gear wheel 54 on an exit axle 56, connected to a downwardly projecting axle 14. The gearbox is of the sealed, non-lubricated type, whereby the device is well suited for mounting in tanks, e.g. for foodstuffs and chemicals.

The supplied fluid flows or is forced into the housing of the apparatus (4) through the openings 28 and 24 and from there through a hole 58 in the bottom to a draining chamber 60, from which the downwardly directed pipe 10 exits.

The adjustment openings 28 are shown having a rectangular form, but in practice it may be preferred to make them tapering towards the top in order to achieve a more accurate adjustment in that area, where the openings are only slightly open. It should be made clear that this area of adjustment would be used fairly seldom, as it is normally the least part of the fluid that is led through the turbine.

It should be emphasized that the adjustment of the turbine speed for the shown principles of adjustment reliably takes place with near instant effect. This is important during the above-mentioned cyclic control, where the optimum is to perform fast adjustments, e.g. when a cleaning jet passes over a joint between two surfaces in the tank.

On the whole, the cyclic control is an important and, moreover, independent aspect of the invention. When cleaning crude oil tanks (see the above- mentioned GB-A-,2,028,113), the problems are less since it is possible to use large amounts of oil without any significant consequences and also with a theoretical possibility of recycling the oil. Correspondingly, a standard setting can be used for the apparatus, giving a suitable closely-meshed pattern of cleaning. Hence, the flushing apparatus can be adapted to the tank for the movement of the flushing head, e.g. through cam control as shown in GB-A-2,028,133.

In connection with tanks for many other fluids and hence other cleaning fluids, it is necessary to adjust the cleaning devices very accurately in order to avoid unnecessary over-consumption of cleaning fluid and in these cases a compromise has normally been made, where the cleaning in certain limited areas is less than perfect, while the general result is satisfactory, and even better than required in places. This is true to a greater or lesser degree depending on the type of product the tank is being cleansed of.

If a dynamic computer control according to the invention is used, it is possible to control both the cyclic variations and the general cleaning pattern in such a way that a high degree of optimisation can be achieved. The cyclic variations can be determined in a control program, which will be closely connected to the construction of the tank and the placing of the flushing head in the tank, while additional programs or other means (e.g. in case of fluctuations of the supply pressure) can be used to determine whether the mesh of the cleaning pattern should be greater or less according to need, or for the occasion when an operation requires variations in the mesh size. For difficult tasks it may be required to use both high pressure and a fine-mesh pattern.

Note that this form of control can be used for all possible types of tanks, mobile and stationary, and that it is irrelevant for the principle of control whether the adjustment is carried out in one way or the other. For all practical purposes, the cleaning apparatus or the flushing head can be driven by a controlled electric or other type of motor, or a remote-controlled gear transmission between a fixed motor and the flushing head can be used. It is within the scope of the invention to control the two main movements of the flushing head independently using suitable driving and adjustment means, e.g. by supplying means for controlled turning of the lower, otherwise fixed toothed gear, which when the flushing head is rotated causes the vertical rotation of the nozzles.

It should be made clear that what is achieved by the dynamic control is a significant reduction in the demand for compromise solutions, regarding the size of the over- and understeering respectively, which occur for these solutions. The advantages of this will be very noticeable, even when operation with total lack of compromises is not achieved. For instance, it has been found that it is perfectly possible to keep the twin jet nozzles 18 even if the ideal condition for the control is a single nozzle. It must also be mentioned that the term "tank" is used in the widest meaning of the word, that is as any type of open or closed container, which is suitable for cleaning using the described method.

Claims

PATENT CLAIMS

1. Tank cleaning system preferably for flushing cargo tanks in tankers, including a driving system consisting of a turbine placed in a turbine pipe and a gear box, which is driven by the turbine and which, via an outlet axle, drives a flushing head, which turbine is supplied with cleaning liquid under pressure and emits outlet liquid to a collecting chamber from where it is conducted to the flushing head, which collecting chamber is, moreover, connected to the inlet side of the turbine by means of an adjustable by-pass valve for adjusting the working speed of the turbine, characterized in that the turbine's inlet pipe for cleaning liquid is formed as a straight pipe of significant length, possibly connected to an arched pipe bend for side introduction of the cleaning liquid, and that the by-pass valve is arranged in relation to one or more side openings in the said inlet pipe and collecting chamber.

2. System according to claim 1, characterized in that the by-pass valve is arranged as an adjustable throttle valve directly on the exterior of the inlet pipe.

3. System according to claim 2, characterized in that the inlet pipe extends down into the collecting chamber, where the turbine is also situated, and that the throttle valve is freely mounted in such a way that the by-pass liquid is forced without guiding from the side openings directly out into the collecting chamber.

4. System according to claim 3 characterized in that the throttle valve is formed from a circular body arranged outside the inlet pipe and possibly provided with one or more holes. The circular body is arranged to be moved axially or circumferentially with the help of operating means, which have manoeuvring organs projecting up through the upper part of the collecting chamber.

5. System preferably according to claim 4, characterized in that the manoeuvring organs for the by-pass valve are connected to a remote control device arranged outside the collecting chamber.

6. System according to claim 3 characterized in that the gear box is also arranged inside the collecting chamber, i.e. as a sealed, dry, non- lubricated unit, which is cooled by the surrounding flow of cleaning liquid through the collecting chamber and down under the turbine.

7. System according to claim 2, characterized in that the side opening or openings in the inlet pipe have increasing/decreasing width seen in the direction of adjustment of the throttle valve.

8. System according to claim 5 characterized in that it further includes a steering apparatus for continuous cyclic adjustment of the by-pass valve.

9. System according to claim 1 characterized in that under the bottom of the collecting chamber an outlet chamber is arranged, which conducts the liquid from the collecting chamber to a downward-leading pipe around the downward-moving outlet axle of the gear box.

10. System according to claim 1, characterized in that the flushing head is of dual rotating type, with one or more nozzles, which are rotated continuously in a vertical rotation plane at the same time as they are rotated in the horizontal plane.