GB2337114A - Detecting and locating fluid leaks through the wall of a vessel - Google Patents

Abstract

A method of detecting and locating fluid leaks through the wall of a food processing vessel comprising scanning the vessel wall surface with a thermal imaging camera by aiming the camera to detect localised spatial temperature differentials on the wall surface, and continuously analysing the thermal image for such a spatial temperature distribution that is indicative of a leak at a region which leak is of sufficient magnitude to cause fluid movement through the vessel wall and recording the position of the region, the method involving introducing as the fluid to one side of the vessel wall air or another fluid, not being a supercooled gas such as liquid nitrogen or solid carbon dioxide and wherein there is a pressure differential across the vessel wall in order to force the said fluid movement through any leak or leaks in the vessel wall and wherein there is substantially no temperature differential across the vessel wall. In a method of locating leaks S in the wall of a food processing vessel 1 using a thermal imaging camera 6, a pressure differential is created across the wall so that a fluid is forced through a fault. The thermodynamic throttling effect creates temperature variations that can be detected with the thermal imaging camera without a temperature differential across the vessel wall.

Description

- j 2337114 METHOD AND APPARATUS FOR DETECTING AND LOCATING FLUID LEAKS

THROUGH THE WALL OF A VESSEL This invention relates to the detection of leaks through the walls of food processing vessels. The invention is useful for the detection of leaks in food processing vessels such as, for example, storage tanks, processing equipment, and refrigerated food storage vehicles and rooms.

Vessels used to store or hold liquid food products are prone to leaks, mainly caused by ageing. The impact of such leaks on the product varies according to the use of the vessel. In some cases serious contamination of the product can occur, which can lead to the product being discarded or recalled from retail outlets, either of which can be very costly.

In each case there is also a significant cost in diagnosing the leak, finding it, and rectifying it using traditional methods. Present preventive techniques often involve the shutting down of a plant or process, and the erection of expensive access equipment is often required. In addition, known techniques involving the use of dye penetrants to cover internal surfaces of the vessel can result in a leak being missed due to the dye being washed out of the flaw during removal of the excess dye.

It is an objective of the invention to improve on the existing methods of location and detection of fluid leaks in food processing vessel walls, including mitigating some or all of the disadvantages mentioned above.

1 Further, in any industry where freedom from bacteriological contamination is important, continual and sustained attention must be given to physical cleanliness and periodic sterilisation to ensure no traces of bacteria remain in preparation and receiving vessels, process plant, implements, transportable containers, and like instruments of 5 activity.

Much industrial plant is of complex internal design, and although TIP" an industrial cleaning process - may be done methodically and thoroughly, a risk remains that the CIP cleaning agents have not been totally effective an all surfaces, corners and crevices of food processing vessels.

An aim of the present invention is to provide a method of leak detection and which is easily adaptable or usable to also check for the presence of bacteria in the food processing vessel.

Prior art methods and apparatus for detecting flaws in walls of buildings and other objects by thermal imaging are described in FIR 2 453 406 and JP 58-124938. A method for detecting microbial growths on packaging using thermal imaging is also disclosed in FR 2 182 443. A method and an apparatus for detecting defective portions of an non-exposed outer surface of a pipe are disclosed in EPO 333 100, over which the present invention is characterised. In none of these prior disclosures is there use of thermal imaging to detect fluid leakages from a vessel.

2 1 According to the present invention there is provided a method of detecting and locating fluid leaks through the wall of a food processing vessel comprising scanning the vessel wall surface with a thermal imaging camera by aiming the camera to detect localised spatial temperature differentials on the wall surface, and continuously analysing the thermal image for such a spatial temperature distribution that is indicative of a leak at a region which leak is of sufficient magnitude to cause fluid movement through the vessel wall and recording the position of the region, the method involving introducing as the fluid to one side of the vessel wall air or another fluid, not being a supercooled gas such as liquid nitrogen or solid carbon dioxide and wherein there is a pressure differential across the vessel wall in order to force the said fluid movement through any leak or leaks in the vessel wall and substantially no temperature differential across the vessel wail.

In order that the invention may be better understood, examples will now be given with reference to the accompanying drawings, in which:- Figure 1 is a diagrammatic sectional view of a non-jacketed food processing vessel undergoing testing in accordance with a preferred form of the invention; Figures 2 and 3 are views corresponding to the view of Figure 1, of a jacketed vessel undergoing a different form of test in accordance with the invention; de, 3 ,R- - 44, c se- onal view of an insulated compp=ent ofEa vehicle, Fignize 4 is a dia-!zr;;TnTn2Ti ---ti 1 undergoing another form of the testing method of the invention; Figure 5 is a half-tone reproduction in black and white of five coloured ilifra-red th=oe:ra,Dhs of different defecu; 1 Figure 6 is a half-tone reDrodudon in black and white of an infra-red thermog-,p-Dh of a siziniess steel plate with bacterial growth on it.

Refe-11mg firstly to Fig. 1, a single-skinned food processirls! vessel 1 has a product L-Jet 2 and a product outlet 3. Any product contained in the vessel will be cont;:-.n,izaied from the a=, osphere, e.g. by air- borne bacteria, if any 1e2.-s are not found 0. 11 and remeded. To test thevessel for leaks the inlet 2 is sealed by a suitable closure 7 and a te-.htici2n T enters the vessel 1, using breathing appararms if ne-. essa7),. A fanz - type extractor 4 is coupled to the outlet 3 and another technician. (noz shown) working outside tb., vessel turns on the fan to draw air out of the product c'z=-'z)e7 and thereby create a pressure diffe-,=tial between the inside of the vessel and the exze-,aal atmosphere.

.L X 10, N 2 M When the pressure inside the vessel falls to less than (2 psi) the first techm.cian T uses thermall imagging equipment 6 to scan the =er surface of the vessel Any flaws in the wall will admit a sue= of W1 S into the vessel, resultinE in a localised zemperarure drop which will be rendered visible trou Eh the imagging equipment 6. The positions of any leaks are noted and the appropriate rej2ir work can then be carried out before re-commissio ='!z the vessel.

1 p 1 1 Fies. 2 and 3 show azother form of vessel 11 Of th kind'v..'E'c' 's provided ---1. - - U=.

alacket 20 to contain el.,hel a heal-ir-suladn-2 mat 42-1 or a liquid cooliz.12 =.di If any leaks should occur tE-Ouzh the inside wa-11 ofthe vessel, 2---v P---- dUcz tbe,--ssel 1 M1 (e.g. milk) will either be contaminated from the external atmosphere in the case of heat insulation, or from the cooling medium itself in the other case.

In Fig. 2, the illustrated vessel 11 has manway or access port 10 and product inlet and outlets 12 and 13 respectively. The jacket 20 has a coolant inlet and outlet 21 and respectively. Any flaws in the wall of the vessel 11 will thus admit coolant (e.g. water) from the jacket 20 into the vessel, contaminating the contents. To test the vessel for leaks, product and coolant are first removed from the respective compartments. The coolant jacket 20 is then lightly pressurised, e.g. to around 1.4 x 10, Nm-1 (2 psi), through the inlet 21 with the outlet 22 being sealed by a suitable closure, or vice versa.

A technician enters the product compartment of the vessel through the manway 10, using breathing apparatus if necessary. The technician then views the inside surface of the vessel using suitable thermal imaging equipment. Any flaws (e.g. cracks and pinholes) in the vessel wall are rendered visible through the equipment due to changes in temperature of pressurised air entering the product chamber from the coolant jacket 20. Again, the position of any leaks can be noted for repair.

Any defects present in the wall can be confirmed and highlighted by spraying soapy water or the like onto the defect so that bubbles will appear as air enters the product chamber.

Special access equipment may be necessary, depending on the size of the vessel.

Fig 3 illustrates an alternative leak detection method which can be used with insulated vessels where it is impractical to drain off the product. The product chamber is filled with product P at a temperature which is different (higher or lower) than the external temperature of the vessel. The product chamber may be pressurised or the hydrostatic pressure of the product may be utilised to cause the product to penetrate any flaw in the wall of the product chamber. Due to the temperature difference between the leaking product and the external temperature the position of the leak can be detected.

-41 l Fig. 4 illustrates a similar method to that described in relation to Fig. 1, being used to check for leaks in a food processing container such as a refrigerated room or refrigerated vehicle 30, of the kind which generally contains food products requiring that a low temperature be maintained to ensure longer life. From time to time leaks may occur through the insulated wall of the room, causing an internal temperature rise and increased risk of product failure. When such vehicles are manufactured or repaired it is very difficult to test them for leaks using known testing methods.

To test the room or vehicle for leaks the inside temperature of the refrigerated compartment is reduced below external air temperature using the existing refrigeration equipment, and the internal surfaces are viewed with thermal imaging equipment. Any cracks 32 will be visible from inside the container using thermal imaging equipment, due to changes in surface temperature between the inside and outside of the container.

Sinc e the process is quick and inexpensive to perform, the container can be checked for leaks at regular intervals allowing flaws to be detected before any serious contamination occurs.

The thermal imaging equipment used in the method of the invention may comprise a conventional infra-red thermal imaging camera and a computerbased disk storage system. Images from the camera are stored on disc so that they can then be improved by computer-aided enhancement techniques to reveal changes in surface tempertures. The resulting processed images are capable of assessment and analysis by computer.

C 6,---7 In one preferred system, the surface. of &c vessel is s anned by an operator aiminR a heat sensitive cam, cr-a which sends its to an on board computer with disc drive, equipped with a monitor and a video tape rec- order. The irnages stored on the, computer disc are then loaded into a second, more powerful computer equipped with an image enhancement program, to enable the ternperarure r?-n!2ts to be raised and cross sectional temperature gradients to be plotted.

Although air is the most convenient eas to use it will be appreciated that other Eases can be used, internally -or exiemzlly.

The abillry to detect a leak usine ther-mal imp-szlnp- in this svay relies on the existence of a temperature dif-ier-ential between he inside and the outside sur-faces of ch.. vessel wall, in the case that there is no pressure dif-Terence. Ifthere is a pressure 1 if there is no iemDe.-a7.-,r.. d.:-ierence in bulk. the difference, how ver, even 1 1 1 the m. odynamic cf-Tect of a jet of fluid passing uhrough a nz7,o\v 2.5 11 elliters or leaves the vessel hrouch the defect, and the ccrsen.utnt fluid rurbulence, give, rise to a distinctive thermal partern. For example, hot air spewine throuch a crack in the wall of a hot air dryer will be discernible by the use CL a the. movision camera, as a themnal 2.nomaly. The heat dis:rilbution on the colder side c.-^ the wall is po,,- ,a),ed on a video monitor, and a therTnal anomaly is revealed as 7- patch of different colour on the monitor. The posizional information of such the:-,,,?1 anomalies can be recorded on a synchronised video camera, operated concur-,entjy..,-ith the therm, ovision camera, providing a thermal and visual presentation of the ir.,s-,zlla:ion being scanned. An experienced operator, viewing the information presented, is able to difT.,-entiat., between a hole in a contaJninR wall and local thinnire of Th.. wall maiedal. Anomalies can also be printed on a thermograph, to provide a pc.-m, anent record, this preferably includes posifional information for the twRez. obtained auto rnati call y frorn the video camera or entered manually e.g. from a keybce:d. Such is the sens'lvlzv of this process that leakscan be benea:h claddins: and Insulation. E== ples o17i,pical themnal 1m22es 2:e shown in Fleure 5.

An example will now be given of a supplementary application for the aforedescribed methodology which, if used, is used in tandem to the leak detection method.

Bacterial deposits are sources of radiant heat, and are therefore detectable by suitable means. If a sufficiently sensitive thermal detector is aimed at the surfaces, corners and crevices of any container or implement concerned, bacterial deposits will be detected and be capable of electronic portrayal on a suitable screen, through a suitable amplifier. In this way, the presence or absence of bacterial deposits can be confirmed.

In practice, as with the leak detection, the thermal detector is installed in a mobile, self-contained hand-held camera gun which can be aimed as desired, and on which the thermal detection sensitivity can be varied to permit a detailed review of areas under surveillance. Thermal images can be stored on a floppy disc in an integral computer, for later detailed assessment through an enhancement program.

Just as the apparatus can detect a thermal anomaly due to the existence of a leak on the inside or outside of a containing wall, it can also detect an anomaly due to the presence of living cells, eg bacteria. Bacteria prejudicial to the cleanliness of the good product concerned will be on the food side of any container, and this is where the thermal imaging camera is used, after regular operations to clean the inside, although the principle could apply to any similar situation. Figure 7 shows a portion of the internal surface of a milk tanker which, after cleansing, was splashed with a small quantity of milk.

Claims (4)

1. A method of detecting and locating fluid leaks through the wall of a food processing vessel comprising scanning the vessel wall surface with a thermal imaging camera by aiming the camera to detect localised spatial temperature differentials on the 5- wall surface, and continuously analysing the thermal image for such a spatial temperature distribution that is indicative of a leak at a region which leak is of sufficient magnitude to cause fluid movement through the vessel wall and recording the position of the region, the method involving introducing as the fluid to one side of the vessel wall air or another fluid, not being a supercooled gas such as liquid nitrogen or solid carbon dioxide and wherein there is a pressure differential across the vessel wall in order to force the said fluid movement through any leak or leaks in the vessel wall and wherein there is substantially no temperature differential across the vessel wall.
2. 2. A method according to claim 1 or 2 further comprising continuously analysing the thermal image for a spatial temperature distribution indicative of the presence of localised bacterial growth on the wall surface.
3. 3. A method as claimed in claim 1 wherein the fluid is air.
4. 4. A method of detecting leakages through the wall of a food processing vessel substantially as hereinbefore described with reference to any suitable combination of the accompanying drawings.

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