DESCRIPTION

This invention concerns leak testing.

Vessels for containing or carrying gas or liquid need to be leak free and, therefore, have to be tested some time before installation and preferably before despatch from manufacturing plant. That is especially significant for vessels such as central heating radiators that are formed by welding together of parts around their periphery. One standard leak testing method is to fill a radiator with water and then pressurise it. Any leaks will be apparent from any escape of water.

The other standard leak testing method is to fill the radiator with compressed air and then to immerse the radiator in water. If a leak is present, it will be apparent by escape of bubbles from the radiator.

These testing methods are usually carried out in the production line between the welding and painting stages, so that, in both cases, the radiator has to pass through a drying stage before painting. That slows down production and increases the cost of a radiator.

Secondly, the leak testing stage requires personnel for inspection and handling of the radiators. Again this slows down production and increases cost.

Thirdly, these leak testing methods are not suitable for use on already painted radiators in case the finish is damaged during handling.

Fourthly such leak testing methods are not ideal for other items, such as electric shower units, where immersion in or filling with water when a leak exists can damage electrical components. In other words, when these methods are used on items having electrical components and a leak is detected, the item has to be discarded rather than rectified.

An object of this invention is to provide a leak testing system for vessels for containing or carrying gas or liquid substantially avoids the above-mentioned disadvantages.

According to the invention there is provided a method of leak testing a vessel comprising the steps of introducing a gas under pressure into the vessel, the gas being at a temperature other than ambient temperature and detecting leakage of the gas from the vessel by infra red detection means.

The invention further provides apparatus for leak testing a vessel comprising means for introducing a gas into the vessel under pressure and at a temperature other than ambient temperature and infra red means for detecting leakage of the gas from the vessel.

The gas for leak-testing is preferably compressed air. The gas is preferably at least at 2°C above or below of ambient temperature. The gas is preferably supplied from a compressor and preferably passes through a chilling zone or heating zone before introduction to the vessel under test.

The means for detecting gas leakage may be an infra red camera, scanner or sensor which can detect presence of escaped gas due to its temperature difference relative to ambient temperature. The detecting means may simply be arranged to transmit an alarm signal when a leak is detected,

so that the vessel being tested can be removed from the production line.

Additionally or alternatively, the detecting means can be arranged to transmit a signal corresponding to a condition detected for storage and/or comparison with stored data, whereby review and analysis of a detected fault is possible. In particular temperature profiles and thermograms may be generated for a vessel under test. For this purpose, the infra red scanner may be arranged to transmit signals to a computer for generation and storage

of profiles and thermograms.

The invention will now be further described, by way of example only, with reference to the accompanying drawing, which shows schematically a system for leak testing a central heating radiator.

Radiators 10 are manufactured on a production line including the stages of welding and finishing/painting. Between these stages is a leak testing stage 12. In this stage a welded radiator 10 is filled with compressed air under pressure from a compressed air supply 1 via a chiller/heater 16.

The pressurized radiator is then passed under an infra red scanner 18. The scanner 18 may be of the Thermoprofile 3 Series type as manufactured by Age a Infrared Systems which can produce a full colour thermal contour map of a radiator, whereby escape of chilled/heated air from the radiator will show up. The parameters in the operating software of the scanner can be set to detect the approximate temperature of the chilled/heated compressed air in the radiator, whereby its escape from a leak can be detected. The scanner 18 is connected to an alarm 20, whereby a visual or audible alarm signal is generated if a leak is detected. When an alarm signal is generated, the

radiator can be removed from the production line for reprocessing. The scanner 18 may also be connected to a computer 22 in order to store data, such as temperature profiles and full colour thermograms, from the scanner.

The stored data can be compared with standard data, so that review and analysis of detected faults can be carried out.

The scanner 18 may further be connected to a production process controller 24 via a scanner controller 26, whereby the production line can be controlled with reference to detection of leaks, e.g. the production may be stopped on detection of a leak in a radiator to allow removal of the faulty radiator from the line.

It will be appreciated that, whilst the invention has been described specifically with reference to leak testing of radiators, the invention may be used for testing leaks in different vessels especially tJiose which can be pressurised. The invention is particularly suitable for use with vessels where leak testing using water is undesirable, such as those containing electric/electronic components that could be damaged by leaking water.