This invention relates to magnetic filters or strainers, in particular for use in fuel pipelines, for example for removal of magnetic, ferromagnetic or paramagnetic particles from petroleum products, such as liquid fuels, for example aviation kerosene.

Fuel such as aviation fuel being delivered to a fuel delivery facility, for example at an airport, may contain contaminants, for example rust particles, from the pipeline or from transport storage such as the hold of a ship. Therefore it is required to filter such fuel before it is dispensed for use.

Fuel filters are well known in the art and usually take the form of in line filtering materials, such as a paper, mesh, fibrous or woven filter cartridges. The fuel is passed through the filter material such that any contaminant particles are collected on the upstream surface of the material. A problem with these filters is that they have to be removed and cither cleaned or replaced periodically in order to remove the contaminants which gradually block the filter material. Furthermore the pressure differential across the filter builds up as the filter becomes dirty, requiring more energy to pump the fuel through the filter. The magnitude of the pressure differential is an indication of the state of the filter, and therefore can be used to ascertain when the filter should be removed and replaced. This system of filtering is costly in terms of replacement costs and energy costs.

Magnetic filters are known, for example for use in domestic heating systems. Λ magnet rod is inserted in a thin walled tubular housing extending into the pressure vessel. The magnets attract debris in the fluid, in particular magnetic iron and steel particles such as rust, which collects around the tube. The system will need cleaning when sufficient debris has built up to form a barrier between the magnets and the fluid, which reduces the efficiency of rust collection due to the radial distance of the new material being collected from the magnetic core, This can be determined by visual inspection. However such a filter is not suitable for high pressure environments such as fuel pipelines, since it would be necessary for the tube to withstand a very high pressure differential between the fuel in the vessel and atmosphere. Furthermore it is difficult to determine when the filter is clogged since visual inspection would require the system to be drained.

Magnetic filters have been proposed for use in pipelines comprising a pipe section of increased diameter, with a large aperture formed in the pipe wall for receiving a magnet filter unit. The unit comprises a plurality of filter rods extending parallel to each other and connected at one end to an end plate for fitting into and securing around the aperture. A disadvantage of this arrangement is that 'dead ⁵ zones exist around the rods, commonly amounting to around 30% of the cross-sectional area of the pipe. Also, such a system is not practical for use in large or high pressure pipelines, or those carrying hazardous fluids, since the unit would be extremely heavy and cumbersome to manipulate due to the need to remove a large pressure containing flange with multiple magnetic rods, and the

requirements for sealing around the end plate would be extremely difficult to achieve. It has therefore been difficult to use magnetic filters for fuel pipelines. The present invention aims to alleviate some or all of these problems.

According to the present invention, there is provided a magnetic filter carriage for use in removing magnetically susceptible contaminants from fluid in a fluid flow, the caniage comprising a frame arranged to support a plurality of elongate magnetic rods, such that the rods are each supported at both ends thereof in a fixed orientation, the frame being adapted to be mounted within a pressure vessel across the direction of fluid flow between a fluid inlet and a fluid outlet of the pressure vessel.

As used herein, "magnetically susceptible contaminants" shall mean contaminants that are attracted to the source of a magnetic field applied to the fluid within which the contaminant is contained, such as the magnetic rods in the case of the present invention.

The magnetic rods of the present invention are or comprise a strong permanent magnet or magnets, preferably a rare earth magnet, and are constructed such that the magnetic rod is resilient to the fluid within which it is to be used. One particularly suitable type of magnetic rod comprises elongate tubes containing a plurality of magnets within the tube, wherein the magnets are arranged end-to-end within the tube, preferably the magnets contained within this form of magnetic rod are rare earth magnets. Suitable magnetic rods which may be used in the present invention would be known to a person skilled in the art.

Since the magnetic filter caniage can be provided directly in a sealed pressure vessel, there is no requirement for it and the components of it to be manufactured such that they are able to withstand a high pressure differential, so the magnetic rods and the means by which they are mounted may be constructed in a way that does not provide high levels of resistance to pressure differentials and may thus be lighter and cheaper. Furthermore, the magnetic filter caniage is a standalone unit which is separate to and can be completely inserted and supported within a pressure vessel, which simplifies the construction of the pressure vessel and reduces the risk of leakage.

The magnetic filter carriage may have a cross-sectional area which receives at least about 90%, or at least about 95%, of the fluid flow through the pressure vessel, such that efficiency of the removal of the magnetically susceptible contaminants is increased.

Whilst it is not essential to the magnetic filter carriage of the present invention, in order to assist in the handling of, loading in to, or removing of the magnetic filter carriage in a pressure vessel, it may be preferable that the frame of the magnetic filter carriage is adapted to be slidable within the vessel. Thus, in one embodiment of the present invention, the magnetic filter carriage may comprise guide members for cooperating with

corresponding guide members located within the pressure vessel; alternatively, other slidable arrangements such as rollers or wheels may also be used. Thus, through use of such means, the magnetic filter carriage may easily be lifted or lowered out of or in to the pressure vessel, or be slidable in to or out of the pressure vessel through an arrangement in another orientation such as horizontally.

The frame of the magnetic filter carriage is configured to support a plurality of elongate magnetic rods. In some embodiments of the present invention, the frame of the magnetic filter carriage is arranged to support the magnetic rods such that they extend substantially parallel to each other.

In one embodiment of the present invention, the magnetic rods may be conveniently mounted in two or more cassettes, each cassette comprising a plurality of magnetic rods, such as from two to ten magnetic rods, for example two, three or four magnetic rods, wherein each of the magnetic rods in the cassette is mounted to one or more blocks or plates, preferably being mounted to the blocks or plates at or adjacent the ends of the magnetic rods. Whilst not essential to the present invention, the magnetic rods may be conveniently mounted in a parallel or approximately parallel within each cassette. The cassettes may then be removably mounted to the frame to form the magnetic filter carriage. Thus, through us of such an arrangement, the handling of the magnetic filter carriage may be made easier since the removal of one or more of the cassettes will reduce the overall weight of the magnetic filter carriage. Furthermore, since each cassette will comprise a reduced number of magnetic rods compared to the magnetic filter carriage, each cassette will be lighter and easier to handle compared to the magnetic filter carriage, and may easily be detached from the magnetic filter carriage to facilitate easier or more convenient cleaning and/or replacement of the magnetic rods.

According to another aspect of the present invention there is provided a magnetic filter system comprising a pressure vessel and a magnetic filter carnage as defined above. The pressure vessel preferably comprises substantially parallel opposed side walls on which guide members, such as tracks or rails, are mounted, the guide members being configured to cooperate with guide members, such as tracks or rails, present on the magnetic filter carriage. Alternatively, the pressure vessel may be provided with internal fitments for mounting the tracks or rails, or may be tapered, for example in a ' V shape, to cooperate with the magnetic filter carnage which may have a corresponding shape. In some cases, the magnetic filter carriage may be formed in an irregular shape for fitting into a correspondingly shaped housing in the pressure vessel.

The pressure vessel also preferably comprises an openable lid or hatch, preferably said lid or hatch is of sufficient dimension so as to allow insertion and removal of the magnetic filter carriage in to and out of the pressure vessel. The pressure vessel is not limited in shape, however, conveniently the pressure vessel may be substantially cylindrical in shape. When the pressure vessel comprises a hatch or lid, the location of the hatch or lid is not limited and may be position such that it allows convenient access to the magnetic filter carnage in the location where the pressure vessel is located, for example the hatch or lid may be at the top should it be desirable to access the magnetic filter carriage from above, for example to enable insertion and removal of the magnetic filter carriage by a lifting and lowering means; or it may be located at the side of the pressure vessel should it be desirable to access the magnetic filter carriage from the side, for example to enable horizontal insertion and removal of the magnetic filter carriage. If the pressure vessel is substantially cylindrical in shape and is configure such that the longitudinal dimension of the pressure vessel is perpendicular or at a tangent to one or more of the inlet and outlet pipes to the pressure vessel, any hatch or lid that may be present in the pressure vessel may conveniently be located at the end of the cylindrical section of the pressure vessel.

The magnetic filter carriage and system of the present invention may be used in pipelines used for transporting any fluid or other substance with fluid-like behaviour; preferably, the magnetic filter carriage and system of the present invention may be used in pipelines used for transporting liquid. In one particular embodiment of the present invention, the magnetic filter carriage and system of the present invention is used in pipelines used for transporting petroleum products, more particularly the magnetic filter carriage and system of the present invention may be used in pipelines used for transporting liquid fuels, such as aviation kerosene or aviation gasoline.

The magnetic filter carriage and system of the present invention may conveniently be suitable for use under the following operating conditions: operating pressures in the range of from 2 to 100 bar, such as pressure in the ranges of from 3 to 100 bar, 5 to 80 bar, 5 to 70 bar, 5 to 50 bar, 10 to 40 bar, or pressures in the ranges from 2 to 10 bar, 5 to 10 bar or 30 to 100 bar incoming liquid flow rate in the range of from 20 to 2000m ³ per hour, such as incoming liquid flow rates of from 20 to 1000 m per hour, 100 to 800 m per hour, 100 to 500 m per hour, or 100 to 400 m per hour, or alternatively flow rates in the range of from 500 to 2000 m ³ per hour or 750 to 1500 m ³ per hour.

Thus, the pressure vessel is preferably a pressure vessel configured to contain fluid at a pressures in the range of from 2 to 100 bar, such as pressure in the ranges of from 3 to 100 bar, 5 to 80 bar, 5 to 70 bar, 5 to 50 bar, 10 to 40 bar, or pressures in the ranges from 2 to 10 bar, 5 to 1 bar or 30 to 100 bar.

The pressure vessel is preferably a pressure vessel configured to contain fluid under pressure at temperatures in the range of from -30 to +60 °C, or -10 to +50 °C, or -5 to +40 °C, or 0 to +30 °C.

The magnetic filter carriage is configured to remove magnetically susceptible contaminants fro a fluid flowing at a rate of from 20 to 2000m per hour, such as fluid flow rates of from 20 to 1000 m ³ per hour, 100 to 800 m ³ per hour, 100 to 500 m ³ per hour, or 100 to 400 m ³ per hour, or alternatively flow rates in the range of from 500 to 2000 m ³ per hour or 750 to 1500 m per hour

The temperature range under which the magnetic filter carriage and system of the present invention may be used will be known to the skilled person based on the materials used and the fluid to which the magnetic filter carriage is to be used with. Typically, when the magnetic filter carriage and system of the present invention are used in pipelines for transporting petroleum products, the petroleum products may typically be exposed to the magnetic filter carriage at temperatures in the range of from -30 to + 60 °C, or -10 to + 50 °C, or -5 to +40 °C, or 0 to +30 °C.

The incoming pipeline to the pressure vessel at least 20 meters up-stream of the vessel may typically have an internal diameter greater than 6" (152.4 mm), or greater than

8" (203,2 mm), or greater than 12" (304,8 mm), or greater than 18" (457.2 mm), or even greater than 24" (609,6 mm).

In order that the present invention may be more readily understood, reference will now be made by way of example to the accompanying drawings, in which:

Figure 1 is a perspective view of a filter arrangement comprising a pressure vessel including a magnetic filter carriage;

Figure 2 is a side view of the filter arrangement of Figure 1;

Figure 3 is a perspective view of a filter carriage including filter rods;

Figure 4 is a perspective view of the carnage frame of Figure 3; and

Figure 5 is a perspective view of a rod cassette of Figure 3.

Referring now to Figures 1 and 2, a high pressure pipe line 2 is shown for carrying fluid such as a petroleum product, for example an aviation fuel. A filtration path including a pressure vessel 4 is provided in the pipe line by means of a pair of elbow sections 6, and a pair of large diameter pipe sections 8 on either side of the vessel 4. A bypass flow path is also provided in the fomi of a bypass pipeline 10 for bypassing the pressure vessel 4, with valves 12 for selecting the required path.

Typical dimensions of the pipe might be about greater than or equal to about 6 inches, 8 inches, or 12, 18 or 24 inches with the large diameter pipe being about 0.5 to 1.5 or 1 to 2, 1.5 to 3 metres in diameter, and the vessel approximately 1, 1.5 or 2.0 metres tall, and 0.5 to 2, or 0,5 to 1,5 or 0.5 to 1 metres wide. However, other dimensions and multiple inlets or outlets are also possible.

The elbow sections 6 are each connected through a wall of one of the large diameter pipe sections 8, which extend substantially parallel to the pipe line. The vessel 4 is substantially cylindrical, extending substantially perpendicular to the large diameter pipe sections 8, and the large diameter sections 8 arc connected through the walls of the vessel in opposed relation to provide an inlet 7 and outlet 9 respectively for the fluid flow across the vessel 4. Typical dimensions of the pipe might be about 8 inches, with the large diameter pipe being about 0.5 metre in diameter, and the tank approximately 1.1 metres tall, and 580mm wide. However, other dimensions and multiple inlets or outlets are also possible.

The vessel includes an access hatch 14 at the top, which may be hingedly opened. The vessel 4 supports a magnetic filter carriage 16 extending across the diameter of the vessel perpendicular to the flow direction between the inlet and the outlet. The carnage carries a plurality of magnetic filter rods, as will be described below, for filtering particles from the flow.

Referring now to Figures 3 and 4, the carriage 16 comprises a frame including a pair of side plates 18, a lower guide plate 20 extending between the lower edges of the side plates 18, and a block cage 22 extending between the upper edges of the side plates 18.

The side plates 18 are rectangular, and are each provided on an outer face 24 thereof with a pair of parallel elongate flanges 26 extending along the length thereof and serving as guide rails for cooperating with corresponding tracks (not shown) on the side walls of the pressure vessel 4. The side plates 18 are preferably welded along their short sides 28 to opposing short sides 30 of the guide plate 20, which is rectangular and has a corresponding width. The side plates may alternatively be removable to allow alternative configurations to be used for accommodating different carriage designs.

The guide plate 20 has locating pegs 32 extending from an inner face 34 thereof for locating a plurality of magnet rod cassettes 36. The block cage is also rectangular, and is preferably welded along opposite short sides 40 to the upper short sides 38 of the side plates.

Referring also to Figure 5, each magnet rod cassette 36 is sized so as to be convenient for manual handling, for example comprising three or four long rods 42. The rods 42 each comprise a tube containing a plurality of magnets, as is well known in the art. The rods are each attached at their lower ends 44 to an elongate retaining plate 46 such that the ends 44 are aligned along the length of the plate. The retaining plate 46 also comprises locating apertures 48 between the rods sized to fit over the locating pegs 32 in the guide plate 20 of the carnage frame so as to hold the cassette firmly in place and reduce any flow induced vibration.

At the top end 50, the rods pass through corresponding elongate retaining blocks 52 such that they extend substantially parallel and in fixed relation to each other. Each retaining block 52 has a width corresponding to lengthwise gaps 54 in the block cage 22 so as to fit closely therein when the cassette 36 is fitted in the frame 16 as can be seen from Figures 3 and 4. The block cage 22 additionally has retaining bars 56 which are spaced apart to correspond with the length of each block 52. The blocks 52 are each provided with a handle 58 for lifting the cassettes out of the frame, A retaining frame 60 may be secured to the block cage 22, for example using quick release fasteners 62 to retain the cartridges in the frame. The side plates 18 are each provided with a pair of steel shackles 64 which can be used to lift and lower the carriage 16.

The frame and cassettes are arranged to provide offset rows of rods. Thus in this example there are three rows of two cassettes. The outer rows comprise two cassettes containing three rods each, and the inner row comprises two cassettes, one containing four rods and the other containing three rods.

In use, the hatch 14 of the vessel 4 is opened, the carriage 16 is lowered into the vessel 4, and the hatch is closed. With the valves 12 directing the flow through the filter path, the flow enters an elbow section 6, and is directed into a larger diameter pipe section 8. Consequently, the speed of the flow is reduced. The fluid then enters the vessel 4 through the inlet 7, with the speed once again reduced due to the larger cross-sectional area presented by the vessel, and passes through the filter carriage and between the magnet rods. Particles such as magnetised steel and rust particles are attracted by the magnetic fields and adhere to the rods. The filtered fluid exits the vessel 4 through the outlet 9 into the other large pipe section 8 and back to the pipeline via the elbow section.

As material builds up on the rods, the ability of the magnetic field to capture further particles decreases until the level of filtration achieved falls below useful levels. The rods therefore need to be cleaned or replaced periodically. With this arrangement, each cassette can be separately removed for cleaning or replacement. Thus any damaged or worn cassette can be replaced allowing continued operation.

Additionally each rod may easily be removed from the cassette. The rods may be cleaned using a wash solution which is miscible or compatible with the fluid within the pipe, or with non-compatible liquids (such as water when the fluid is a fuel).