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Research and development
Rose
Poh s n d dovo|opt
Semi-automatic ultrasonic testing of rubber gaskets Specialized ultrasonic test equipment has been designed and manufactured by British Steel Corporation for testing gaskets used in joining natural gas pipelines. The special gaskets are moulded from rubber and have a nylon nose and a compression face of woven nylon fabric. To ensure the soundness of the gaskets the makers, Victaulic, took advantage of the design and research facilities within the British Steel Corporation's Tubes Division (of which they are a member). The test equipment for this application was designed and supplied by the NDT and Control Section at the Research Centre, Corby, UK, and named Ecosonic. The ultrasonic test unit had to be capable of detecting the two types of fault that can occasionally occur during manufacture of these gaskets, namely voids and laminations in the rubber moulded ring and a disbond between the nylon tip and the rubber ring. Ultrasonic detection of these faults was successfully accomplished using a through transmission technique, which requires the gaskets to be rotated through a fixed transducer yoke assembly. Operation of the test unit had to be kept as simple as possible to allow the actual testing to be carried out by unskilled labour. To achieve this the equipment was designed to be semi-automatic in operation in that each gasket in turn would be placed on the test unit, automatically assessed as being 'good' or 'suspect' and then manually removed; a test cycle time of 15 s or less had to be achieved for each of the eight different gasket sizes. To cover the range of gasket diameters, 100 m m - 600 ram, three gasket test c h a m b e r s were required. Depending on the size of the gasket to be tested, one of the three test chambers is placed into the drainage tray containing water. Water from the drainage tray is continually pumped
ULTRASONICS. JANUARY 1980
ent
into the test chamber to maintain a constant level, the excess water overflowing back into the tray. Inside the test chamber there are two sets of gasket locating/drive rolls, which enable the gaskets to be manually inserted and automatically rotated through a submerged transducer yoke assembly. The ultrasonic transducer assembly, comprising a single transmitting element of resonant frequency 2 MHz (element size 25 mm x 10 mm)and a staggered array of six receiver elements, each receiver being 6 mm in diameter, is arranged to test across the thickness of the gasket as it rotates at a constant speed. The testing technique uses the ultrasonic through-transmission method by monitoring the ultrasonic energy loss from the transmitting element to each receiver element resulting from the presence of voids or laminations in the rubber ring. The test unit is semi-automatic in that each gasket, in turn, is manually placed on to the submerged rotating rolls, automatically rotated and assessed as being acceptable or rejectable (visual and audible alarm) and then manually removed. To ensure each gasket is adequately pre-wetted (necessary to
Transducersyokeassembly avoid air bubbles adhering to the gaskets), prior to insertion into the test chamber the gaskets are agitated in an adjacent tray containing a water/Teepol solution. The transmitter element is pulsed at 6 kHz and the single ampNtude of the ultrasonic through-transmission signal received by each of the six receiving elements is monitored sequentially using common amplifier and gate generator modules; this gives an effective inspection prf of 1 kHz. Each receiving channel has a separate sensitivity control and an on/off switch, all six channels not being required when the small and medium-sized gaskets are inspected.
The three test chambers
3
When a gasket is inserted into the test chamber it automatically rotates and the actual test is initiated by depressing an air-operated push button located on the front of the drainage tray. After one revolution the test is completed and either the 'good' or 'suspect' lamp on the small visual alarm unit is illuminated. Measurement of one revolution is accomplished by counting pulses from a small pulse generator located on one of the drive units on each of the test chamber assemblies. The drive rolls rotate at a fixed speed and the test
equ|p
time for a gasket is 4-10 s depending on the gasket size being inspected. Although an oscilloscope monitor is not required for testing purposes the outputs from each channel are available for initial setting up, signal recording and maintenance purposes. Additional features of the electronics include an automatic gain control circuit, a successive loss of signal logic that eliminates the possibility of spurious triggering by single signal loss, and resettable batch counters to provide a record of the
number of gaskets tested and the number deemed suspect. The attenuation in signal amplitude required to trigger the receiver channel outputs is preset to the desired value. Gaskets with simulated defects giving the required signal attenuation are used to check the calibration of the equipment at two-hourly intervals.
British Steel Corporation, Tubes Division, Corby Works, PO Box 10 I, We/don Road, Corby, Northants NN17 IUA, UK
ent
Real-time scanner
Sixteen grey-scale levels can stored.
be
On display recently at GEC's showrooms in London was Telscan, the British company's real-time ultrasonic scanner. The unit consists of a 70 element, linear array probe with thick film circuit switching, connected by a 2.5 m cable to the display module. The display is directly video c o m p a t i b l e and other features included as standard are patient identification using the built-in keyboard, A- and M-modes and frame freeze.
A range of four probes is available at frequencies of 2.2, 3.5, 5 and 7 MHz. The frequency of the probe chosen is a u t o m a t i c a l l y displayed on the screen. Focusing is at a pre-set depth depending on the probe. Variable angle and position calipers are controlled from the front panel and readout is in mm from a LED display. They operate in the frame-freeze or realtime modes and have an accuracy of +0.25 mm.
An A-mode can be displayed with the B-mode display, which also indicates from where the A-mode is being sampled. Variable signal threshold control enables rejection of low-level echoes to optimize image clarity. The transmit power level is less than 2 mW cm -2 and can be varied in 5 dB steps from 0-50 dB. Time gain control has a variable delay from 5-125/1s and a near gain from 0-70 dB. For patient identification two lines of 36 alpha-numeric characters are available, and 11 characters for hospital/department identification can be programmed prior to installation. The unit is easily transported on a trolley, weighs 28 kg and measures 530 x 550 x 260 ram. Power consumption is 120 W. It is currently available in the UK only, but it is hoped to market it elsewhere shortly.
Real-timeultrasonicscanner 'Telscan'from GEC Medical.Probesare availableup to 7 MHz
4
Vein imaging Information was also available on MAVIS (mobile artery and vein imaging system) which the company are developing with P.J. Fish of Kings College Hospital, London. The latest pre-production models, Mavis C, are currently undergoing clinical trials in the UK and USA. The machine performs multiple channel, high resolution mapping of blood vessels using Doppler ultrasonics. Thirty channels are used simultaneously to measure the blood
U LTRASONICS . JANUARY 1980
Poh s n d dovo|opt
Semi-automatic ultrasonic testing of rubber gaskets Specialized ultrasonic test equipment has been designed and manufactured by British Steel Corporation for testing gaskets used in joining natural gas pipelines. The special gaskets are moulded from rubber and have a nylon nose and a compression face of woven nylon fabric. To ensure the soundness of the gaskets the makers, Victaulic, took advantage of the design and research facilities within the British Steel Corporation's Tubes Division (of which they are a member). The test equipment for this application was designed and supplied by the NDT and Control Section at the Research Centre, Corby, UK, and named Ecosonic. The ultrasonic test unit had to be capable of detecting the two types of fault that can occasionally occur during manufacture of these gaskets, namely voids and laminations in the rubber moulded ring and a disbond between the nylon tip and the rubber ring. Ultrasonic detection of these faults was successfully accomplished using a through transmission technique, which requires the gaskets to be rotated through a fixed transducer yoke assembly. Operation of the test unit had to be kept as simple as possible to allow the actual testing to be carried out by unskilled labour. To achieve this the equipment was designed to be semi-automatic in operation in that each gasket in turn would be placed on the test unit, automatically assessed as being 'good' or 'suspect' and then manually removed; a test cycle time of 15 s or less had to be achieved for each of the eight different gasket sizes. To cover the range of gasket diameters, 100 m m - 600 ram, three gasket test c h a m b e r s were required. Depending on the size of the gasket to be tested, one of the three test chambers is placed into the drainage tray containing water. Water from the drainage tray is continually pumped
ULTRASONICS. JANUARY 1980
ent
into the test chamber to maintain a constant level, the excess water overflowing back into the tray. Inside the test chamber there are two sets of gasket locating/drive rolls, which enable the gaskets to be manually inserted and automatically rotated through a submerged transducer yoke assembly. The ultrasonic transducer assembly, comprising a single transmitting element of resonant frequency 2 MHz (element size 25 mm x 10 mm)and a staggered array of six receiver elements, each receiver being 6 mm in diameter, is arranged to test across the thickness of the gasket as it rotates at a constant speed. The testing technique uses the ultrasonic through-transmission method by monitoring the ultrasonic energy loss from the transmitting element to each receiver element resulting from the presence of voids or laminations in the rubber ring. The test unit is semi-automatic in that each gasket, in turn, is manually placed on to the submerged rotating rolls, automatically rotated and assessed as being acceptable or rejectable (visual and audible alarm) and then manually removed. To ensure each gasket is adequately pre-wetted (necessary to
Transducersyokeassembly avoid air bubbles adhering to the gaskets), prior to insertion into the test chamber the gaskets are agitated in an adjacent tray containing a water/Teepol solution. The transmitter element is pulsed at 6 kHz and the single ampNtude of the ultrasonic through-transmission signal received by each of the six receiving elements is monitored sequentially using common amplifier and gate generator modules; this gives an effective inspection prf of 1 kHz. Each receiving channel has a separate sensitivity control and an on/off switch, all six channels not being required when the small and medium-sized gaskets are inspected.
The three test chambers
3
When a gasket is inserted into the test chamber it automatically rotates and the actual test is initiated by depressing an air-operated push button located on the front of the drainage tray. After one revolution the test is completed and either the 'good' or 'suspect' lamp on the small visual alarm unit is illuminated. Measurement of one revolution is accomplished by counting pulses from a small pulse generator located on one of the drive units on each of the test chamber assemblies. The drive rolls rotate at a fixed speed and the test
equ|p
time for a gasket is 4-10 s depending on the gasket size being inspected. Although an oscilloscope monitor is not required for testing purposes the outputs from each channel are available for initial setting up, signal recording and maintenance purposes. Additional features of the electronics include an automatic gain control circuit, a successive loss of signal logic that eliminates the possibility of spurious triggering by single signal loss, and resettable batch counters to provide a record of the
number of gaskets tested and the number deemed suspect. The attenuation in signal amplitude required to trigger the receiver channel outputs is preset to the desired value. Gaskets with simulated defects giving the required signal attenuation are used to check the calibration of the equipment at two-hourly intervals.
British Steel Corporation, Tubes Division, Corby Works, PO Box 10 I, We/don Road, Corby, Northants NN17 IUA, UK
ent
Real-time scanner
Sixteen grey-scale levels can stored.
be
On display recently at GEC's showrooms in London was Telscan, the British company's real-time ultrasonic scanner. The unit consists of a 70 element, linear array probe with thick film circuit switching, connected by a 2.5 m cable to the display module. The display is directly video c o m p a t i b l e and other features included as standard are patient identification using the built-in keyboard, A- and M-modes and frame freeze.
A range of four probes is available at frequencies of 2.2, 3.5, 5 and 7 MHz. The frequency of the probe chosen is a u t o m a t i c a l l y displayed on the screen. Focusing is at a pre-set depth depending on the probe. Variable angle and position calipers are controlled from the front panel and readout is in mm from a LED display. They operate in the frame-freeze or realtime modes and have an accuracy of +0.25 mm.
An A-mode can be displayed with the B-mode display, which also indicates from where the A-mode is being sampled. Variable signal threshold control enables rejection of low-level echoes to optimize image clarity. The transmit power level is less than 2 mW cm -2 and can be varied in 5 dB steps from 0-50 dB. Time gain control has a variable delay from 5-125/1s and a near gain from 0-70 dB. For patient identification two lines of 36 alpha-numeric characters are available, and 11 characters for hospital/department identification can be programmed prior to installation. The unit is easily transported on a trolley, weighs 28 kg and measures 530 x 550 x 260 ram. Power consumption is 120 W. It is currently available in the UK only, but it is hoped to market it elsewhere shortly.
Real-timeultrasonicscanner 'Telscan'from GEC Medical.Probesare availableup to 7 MHz
4
Vein imaging Information was also available on MAVIS (mobile artery and vein imaging system) which the company are developing with P.J. Fish of Kings College Hospital, London. The latest pre-production models, Mavis C, are currently undergoing clinical trials in the UK and USA. The machine performs multiple channel, high resolution mapping of blood vessels using Doppler ultrasonics. Thirty channels are used simultaneously to measure the blood
U LTRASONICS . JANUARY 1980