GB1568968A

GB1568968A - Method and apparatus for testing containers

Info

Publication number: GB1568968A
Application number: GB495476A
Authority: GB
Original assignee: RHEEM BLAGDEN Ltd
Current assignee: RHEEM BLAGDEN Ltd
Priority date: 1977-02-07
Filing date: 1977-02-07
Publication date: 1980-06-11

Description

(54) METHOD AND APPARATUS FOR TESTING CONTAINERS (71) We, RHEEM BLAGDEN LIMITED, a British Company, of 16-18 Hatton Garden, London EC1N 8AT, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a method and apparatus for testing containers and more particularly to the detection of leaks in containers.

The invention provides a method of testing a container e.g. a drum or a drum liner, in order to detect leaks in the container, said method comprising pressurising the container and detecting, in an enclosed chamber having acoustically reflective internal wall surfaces, the presence of any escaping air by means of an ultrasonic detector located within the chamber.

Preferably the ultrasonic detector com- prises at least one piezo-ceramic transducer which is preferably connected to a control cirmit including an indicator.

Preferably the pressure in the container is in the range of 1 to 10 p.s.i. above atmospheric pressure.

Preferably the method comprises the further step of presetting the ultrasonic detector to compensate for ambient noise levels.

The invention also provides apparatus for testing a container to detect leaks in the container by the method described above, said apparatus comprising an enclosed chamber having internal wall surfaces treated to be acoustically reflective and means, e.g. a door or doors or lid, through which a pressurised container to be tested may pass, and an ultrasonic detector located within the chamber.

Preferably the ultrasonic detector com prises at least one piezo-ceramic transducer which is preferably connected to a control circuitry including audio and/or visual indicators.

Preferably the acoustically reflective internal wall surface comprises aluminium foil or polished aluminium, but it may be of any acoustically reflective material.

Further features of the invention will become apparent from the following description, by way of example, of a preferred embodiment of the invention, the description being read with reference to the accompanying drawing which is a diagrammatic representation of a container testing apparatus.

The testing apparatus comprises the following main elements; a testing chamber or booth 10, a transducer 11, a control circuit 12, and indicating means which may consist of a meter 13 and a visual or audio signal 14.

The testing chamber 10 has a substantially sound-proof outer wall 17 which may consist of concrete blocks or any recognised building materials of a suitable soundabsorbing quality and acoustic reflecting inner wall 18 which may consist of aluminium foil, polished aluminium or similar acoustically reflective material. A door (not shown) provides ingress and egress to the chamber and is acoustically sealed when closed.

The transducer 11 is a piezo-ceramic transducer which detects ultrasonic vibrations. Transducers may be positioned at any number of points within the chamber 10, as will be explained below, and may be provided with parabolic reflectors to improve sensitivity and/or give directional capability. The control circuit 12 provides means for tuning, filtering and amplifying the transducer signal or signals. The meter 13 and signal 14 provide a visual and/or audio display which indicates when a leak is present in a container being tested.

Memory modules may be provided in the control circuit when more than one transducer is being used, in order to identify which transducer has received a signal.

The area of the leak may thus be identified.

The transducers may also be mounted on a rotating scanning structure.

The method of testing will now be described. The container 20 to be tested is first pressurised to a predetermined pressure above atmospheric and then sealed outside the chamber, or automatically pressurised after being placed in the chamber.

For this purpose, the chamber may include means to position and pressurise the container. The method of testing of this invention is suitable for any container which is pressurised or non-pressurised in use although it is primarily intended for testing plastics or metal drums and plastics liners for drums. The predetermined pressure within the container will depend on the type and size of container being tested but will generally be in the range of 1 to 10 p.s.i. above atmospheric pressure. Pressurised containers are tested at their filled pressure. While being pressurised a suitable evaporation fluid may be introduced into the container in order to increase the acoustic generation of any leak.

The testing apparatus is tuned to the environmental background noise with the door of the chamber closed so that the meter 13 gives a zero or acceptable low level reading with no container in the testing chamber. The pressurised container or container to be automatically filled is then placed into the chamber and the door closed. If there is a leak in any part of the container the escaping air will set up an acoustic vibration in the ultrasonic frequency band within the chamber. The acoustically reflective walls of the chamber 18 ensure that this vibration reverberates around the chamber and is thus detected by the transducers, irrespective of the position of the transducers in the chamber. The amplified signal from the transducers then causes the meter 13 to register a change and may also be used to trigger a signal 14 such as a buzzer or flashing light.

Finally, if the above test reveals that there is a leak in the container, the position of the leak is located in conventional manner using a hand held detector or using the memory facility if fitted.

A great advantage of the method of testing described is that it is simple to use and is extremely sensitive. For example, in tests on a plastics liner for a steel drum of 30 to 40 thousands of an inch thickness, the liner was pressurised to 2 p.s.i. above atmospheric. The transducer was tuned to 40 KHz and the millivoltmeter was zeroed to the background level of noise. A sound liner when placed in the testing chamber caused no change in the reading of the meter while a liner with a pinhead-sized hole formed therein caused a full scale deflection of the meter.

This sensitivity of leak detection is very important since plastics liners of the type tested are often used in steel drums used to store and transport highly corrosive and toxic substances.

Although the method described above is used to test for any leak in a container, in some applications, a small leak may be acceptable. In this case, the apparatus may be pre-tuned to register only when a leak of greater than a predetermined size is located.

WHAT WE CLAIM IS: 1. A method of testing a container, for example a drum or a drum liner, in order to detect leaks in the container, said method comprising pressurising the container and detecting, in an enclosed chamber having acoustically reflective internal wall surfaces, the presence of any escaping air by means of an ultrasonic detector located within the chamber.

2. A method as claimed in claim 1 in which the ultrasonic detector comprises at least one piezo-ceramic transducer.

3. A method as claimed in claim 2 in which the transducer is connected to a control circuit including an indicator for indicating when a leak is detected.

4. A method as claimed in any one of the preceding claims in which the pressure to which the container is pressurised is in the range 1 to 10 p.s.i. above atmospheric pressure.

5. A method as claimed in any one of the preceding claims comprising the further step of presetting the ultrasonic detector to compensate for ambient noise levels.

6. A method of testing a container in order to detect leaks, substantially as hereinbefore described with reference to the accompanying drawing.

7. Apparatus for testing a container to detect leaks in the container by a method as claimed in any one of the preceding claims, said apparatus comprising an enclosed chamber having internal wall surfaces treated to be acoustically reflective and means, e.g. a door or doors or lid, through which a pressurised container to be tested may pass, and an ultrasonic detector located within the chamber.

8. Apparatus as claimed in claim 7 in which the ultrasonic detector comprises at least one piezo-ceramic transducer.

9. Apparatus as claimed in claim 8 further comprising a control circuit connected to the transducer or transducers, said circuit including audio and/or visual indicators for indicating when a leak is detected.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. control circuit when more than one transducer is being used, in order to identify which transducer has received a signal. The area of the leak may thus be identified. The transducers may also be mounted on a rotating scanning structure. The method of testing will now be described. The container 20 to be tested is first pressurised to a predetermined pressure above atmospheric and then sealed outside the chamber, or automatically pressurised after being placed in the chamber. For this purpose, the chamber may include means to position and pressurise the container. The method of testing of this invention is suitable for any container which is pressurised or non-pressurised in use although it is primarily intended for testing plastics or metal drums and plastics liners for drums. The predetermined pressure within the container will depend on the type and size of container being tested but will generally be in the range of 1 to 10 p.s.i. above atmospheric pressure. Pressurised containers are tested at their filled pressure. While being pressurised a suitable evaporation fluid may be introduced into the container in order to increase the acoustic generation of any leak. The testing apparatus is tuned to the environmental background noise with the door of the chamber closed so that the meter 13 gives a zero or acceptable low level reading with no container in the testing chamber. The pressurised container or container to be automatically filled is then placed into the chamber and the door closed. If there is a leak in any part of the container the escaping air will set up an acoustic vibration in the ultrasonic frequency band within the chamber. The acoustically reflective walls of the chamber 18 ensure that this vibration reverberates around the chamber and is thus detected by the transducers, irrespective of the position of the transducers in the chamber. The amplified signal from the transducers then causes the meter 13 to register a change and may also be used to trigger a signal 14 such as a buzzer or flashing light. Finally, if the above test reveals that there is a leak in the container, the position of the leak is located in conventional manner using a hand held detector or using the memory facility if fitted. A great advantage of the method of testing described is that it is simple to use and is extremely sensitive. For example, in tests on a plastics liner for a steel drum of 30 to 40 thousands of an inch thickness, the liner was pressurised to 2 p.s.i. above atmospheric. The transducer was tuned to 40 KHz and the millivoltmeter was zeroed to the background level of noise. A sound liner when placed in the testing chamber caused no change in the reading of the meter while a liner with a pinhead-sized hole formed therein caused a full scale deflection of the meter. This sensitivity of leak detection is very important since plastics liners of the type tested are often used in steel drums used to store and transport highly corrosive and toxic substances. Although the method described above is used to test for any leak in a container, in some applications, a small leak may be acceptable. In this case, the apparatus may be pre-tuned to register only when a leak of greater than a predetermined size is located. WHAT WE CLAIM IS:

1. A method of testing a container, for example a drum or a drum liner, in order to detect leaks in the container, said method comprising pressurising the container and detecting, in an enclosed chamber having acoustically reflective internal wall surfaces, the presence of any escaping air by means of an ultrasonic detector located within the chamber.

10. Apparatus as claimed in claim 9

further comprising means to indicate the location of a leak detected by the apparatus.

11. Apparatus as claimed in any one of claims 7 to 10 in which the acoustically re elective internal wall surfaces comprises aluminium foil.

12. Apparatus for testing a container in order to detect leaks substantially as hereinbefore described with reference to and as shown in the accompanying drawings.