GB2378641A

GB2378641A - Method and apparatus for cleaning ISO tank containers and the like

Info

Publication number: GB2378641A
Application number: GB0119983A
Authority: GB
Inventors: Alan Turner; Jason Alan Turner
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-08-16
Filing date: 2001-08-16
Publication date: 2003-02-19
Also published as: GB0119983D0

Abstract

Corrosion and like detritus is cleaned from the inner surfaces of ISO tank containers and the like by mounting the tank in its frame 2 in an apparatus which allows the tank to be rotated whilst it contains cleaning adjuvant. In the embodiment the tank in its frame 2 is mounted on a pair of end plates 3 each of which has a circular bearing surface 4. With the plates attached the assembly is supported on driven rollers 7 which contact the bearing surface. When the rollers are caused to rotate the whole tank rotates about its axis. To effect cleaning, the tank is charged with abrasive cleaning medium and then can be flushed with etching agent and if required the surface can thereafter be chemically passivated, still using the apparatus.

Description

TANK CONTAINER REFURBISHMENT DEVICE.

This invention relates to a device to remove the corrosion from the inner surface of tank containers of the type used on road haulage vehicles. The tank, insitu with its metalic housing frame which is used for handling and protection, is lifted from the vehicle and loaded onto the device for processing.

The invention has been particularly developed to address the problems found in existing methods of tank refurbishment.

At present, systems are known that clean the inner surface of tanks, such as mechanized brush systems and jetting systems, which usually gain access to the tank through the man access hatch, but the removal of the corrosion remains a problem, as these systems are not intended to remove significant thicknesses of surface corroded metal. The existing method to achieve these amounts of metal removal requires personnel to enter the tank to grind and then polish the surface. This is carried out in a variety of ways including electric hand operated grinders and polishers. The process is labour intensive and can itself cause damage to the tank surface due to the foot traffic of the operators creating additional scratches and blemishes in the final finished surface. These then act as new corrosion sites which degrade the service life of the refurbished tank.

Description.

According to the present invention there is provided a device which solves the problems with existing methods by providing a mechanised system aided by chemical means which is capable of removing surface corrosion and metal and reducing or eliminating the need for operatives to enter the tank, thus improving process quality.

The present invention is novel, in that the whole tank and its transport frame is removed from the transport means, part filled with abrasive materials, flushing and etching agents and rotated, so that the inner tank surface is refurbished by the action of the charge materials against the tank surface and the action of the chemical means.

Chemical means: The flushing etching chemical means solution, is a mild acidic solution containing inhibitors.

The flushing etching solution reacts with the surface of the stainless steel tank, removing the surface oxide layer, then the abrasive media removes the metal during the tumbling process.

The flushing etching solution also flushes away the debris and helps prevent clogging of the ceramic media. This maximizes the ongoing cutting action and efficiency of the ceramic media.

Mechanical means: The tank and its frame are lifted from the road or other transport system. The transport frame is fitted with end frames, which serve both as a lifting frame and provide the bearing surface locations necessary to locate onto the processing device drive means.

The bearing surface of the end plates may be constructed by way of example, to provide an annular flat, or curved surface on which a series of one or more sets of drive and idler rollers, or gears, may run. Each end of the tank container is supported in this way and the assembly rotated by the drive means.

The annular surfaces may be either concentric to the tank container axis, or offset from it, or elliptical, or the bearing or drive surface axis may be axially offset from one end of the tank container axis to the other. This drive configuration provides an oscillatory or camming movement to the tank container thus enhancing the effectiveness and circulation of the abraisive and polishing media and gives an alternative to the simple axial rotation of the tank. The tank assembly may be driven by any of a number of alternative known drive means, such as a gear upon the axis of the tank or offset from it, which is directly driven by engaging it upon the drive gearing of the apparatus.

The tank is charged with a suitable abrasive material and flushing etching agent, usually but not exclusively via the man access location. The tank is then preferably closed and then rotated or oscillated by the process machinery as described above.

The action of rotation and or oscillation causes the abrasive material in contact with the tank surface to remove metal and the corrosion defects from the surface of the tank. The flushing etching agent is particularly beneficial in the case of a stainless steel tank to minimise the clogging of the ceramic or abrasive media and thus maximise the metal removal capability.

The rotation or oscillation of the tank continues until enough of the corroded surface is removed. Further polishing of the surface is then best achieved by removing the ceramic and flushing agent charge from the tank and introducing a polishing medium which by way of example may be a finer grade and or smaller grade of ceramic material. An aditional polishing medium may also be introduced either at the same time or during one or more following polishing cycles. A flushing agent may still be required during the polishing cycle.

The tank is then discharged using pump or gravity means via the man access hatch or other convenient access.

Following the polishing process either by existing means or the new method as described above, it is normal practice to further enhance the corrosion resistance of the tank surface by a process known as passivation. In the case of a stainless steel tank, this involves the introduction of acids such as nitric or hydrofluric, which removes the nickel and free iron from the outer surface of the tank material, leaving a predominanly chromium rich surface layer, which after flushing with preferably demineralised water, leaves a surface which produces a chromium oxide layer after contact with the atmosphere. This is a known method of achieving the passivated surface and may be performed either on or off the process machinery by means of a spray head introduced through the man access hatch.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which, Fig 1. shows an overall perspective view of the process machinery apparatus.

Referring to fig 1, the device consists of the tank (1), located in its transport, handling frame (2). The assembly of (1) and (2) is mounted in the end location plates (3) which have a bearing surface (4).

The bearing surface (4) of the location plates (3) is supported on rollers, wheels or the like (7), with one or more of the rollers preferably being driven, imparting a rotational or oscillating motion to the assembly, the remaining rollers being idler rollers supporting the rotation of the assembly.

The drive rollers (7) are powered by a geared or belt drive speed reduction system (8) from the drive motor (9). The drive motor may also be a variable speed and or geared motor. The rollers (7) may alternatively be drive and idler gears, which engage with the bearing surface (4), which in that case would be a ring gear.

The process machinery is located upon a steel support structure (10), one end of which may be longitudinally adjustable (11) to accept the mounting of the various standard lengths of tank container onto the process machinery.

The tank (1) is charged with the abrasive medium, which may consist of one or more different types or grades of material (5) and the flushing etching agent (6).

The assembly along with its charge is then caused to rotate or oscillate.

Claims

CLAIMS : 1. A method of mounting a tank container insitu with its transport handling frame onto an apparatus to impart onto the assembly, a rotational or oscillatory movement.
2. A method as claimed in claim 1, where end location plates, which have on them the bearing surface or other drive means, so that the assembly may be loaded directly onto the drive mechanism of the apparatus, are fitted to each end of the tank container transport frame.
3. A method as claimed in claim 1 and 2, where the location plates have axially mounted upon them, a circular structure concentric, or offset from the container, so that when mounted onto the rollers or other drive means of the apparatus, a circular or camming rotation action of the tank container is achieved.
4. A method as claimed in claim 1, 2, and 3, where the container is partially filled with an abrasive medium, so that the rotational, oscillatory, or camming movement of the container, causes the abrasive medium to abrade against the entire inner surface of the container, thus removing corrosion and base material of the container.
5. A method as claimed in claims 1, 2, 3 and 4, where one or more abrasive media may be used at the same time.
6. A method as claimed in claim 1, 2,3, 4 and 5, where one or more abrasive media may be used sequentially.
7. A method as claimed in claim 1, 2,3, 4,5 and 6, where the container may be partially filled with a polishing media.

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8. A method as claimed in claim 1,2, 3,4, 5,6 and 7, where a liquid flushing etching agent may be added to the abrasive or polishing media, to reduce the tendency of the media to clog and chemically aid metal removal by attacking the surface oxide layers.
9. A method as claimed in claim 1,2 and 3, where a liquid passivation acid or chelating agent may be introduced into the tank and the rotation or oscillating action used to achieve total coverage or desired soak time of the tank surface.
10. A method as claimed in claim 1,2 and 3, where the apparatus is mounted upon a ground structure which as adjustable in an axial direction at least at one end, so that tank containers of various lengths may be accommodated.
11. A method substantially as hereinbefore described with reference to the accompanying drawings.
12. An assembly substantially as hereinbefore described with reference to the Accompanying drawings.