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Test Mechanics


There are the various mechanism available, all have their own advantages and disadvantages. A general classification can be made, these are fixed mounting and scanning transducers.

Measurement chamber for 2-50 / 10-110 mm pipes

Flanged Measurement ring for larger 110 mm pipes

Flanged ring on the calibration sleeve.

Transducer holder in the calibration sleeve

Swivel arm, stands alone between the cooling baths

Immersion (Flanged) scanner at the vacuum bath

Immersion (Flanged) scanner at the pressure calibration

The user has to decide how many Measurements (4/6/8...32) on the pipe circumference are necessary and if it needs to be done continuousl,. since the reliability of the fixed transducer mechanism is preferred.

Fixed mounting transducers

In common are 4,6,8 or even more transducers. The advantage is the simplified mechanics, of a ring mounted with transducers. The arrangement is used because it's economic, small and reliable. Further it is common for testing large pipes, thus scanners have a higher costs and need more frequent maintenance.

Measurement Chamber go to Pictures

A measurement chamber is often used for a Diameter of less than 110 mm and usually together with the Ultrasonic diameter option. There is a rising need shows for the floor heating pipe. Because of producer warranty, the in-line measurement is the only solution. In addition, possible break down due to jamming was avoided with automatically releasing, two-piece guidance shells. Even hoses with around 1.5 mm and 0.2 mm wall thickness can be measured just as reliably as pipes with a diameter of 110 mm. Over 110 mm a flanged chamber called AFM is used and here is the pipe guided by a strong mounted ring guidance.

A special method is a measurement inside the vacuum tank at the sizing sleeve.

ultrasonic at sizing sleeve

The design consist of a ring that is mounted at the end of the sleeve and includes the transducers. The individual transducers are placed in plastic holders, each with a water supply to enable an optimal ultrasound signal condition. There are up to 32 transducers available. The alternative method, of mounting the transducers directly in the sleeve, has the disadvantage that a tooling of each calibration sleeve is nesaccary. This configuration has proven itself to be worthwhile, primarily due to its formative help with regard to alignment of the die. The system can be combined with an automatic thermal pipe heating alignment device.

Reversible Scanner

1. Swivel arm Scanner

By means of such scanners, the transducer is measuring the complete circumference of the pipe. The transducer is guided via a prism on the pipe surface. The ultrasonic coupling is done by direct contact by the water path method.With a swivel arm, powered by pneumatics the transducer holder is pressed on the pipe. The mechanics can be easily adjusted to different pipe diameters. During the start up period of the extrusion, the transducer is automatically placed into a parking position. With this scanner, the ultrasonic diameter method can not be adapted. Further, there are disadvantages in measuring small pipe dimensions with fast haul off speed.

2. Immersion Scanner

The disadvantages of the swivel-arm-scanner was an essential impetus to design the immersion scanner. The immersion scanner, also called the flanged-scanner, can be mounted at the front or rear of the extrusion baths. An essential advantage is the non contact immersion method of the transducer coupling, thus they are reversing underwater around the pipe. The alignment is prevented by inlet and outlet rings guiding the pipe. It is also usual that is not necessary to readjust the transducer position with the production of different pipe diameters.

By the use of two transducers, these are installed across from each other, there is the advantage to adapt the measurement of the Outer/Inner diameters .Further, ovalness calculation and an integrated quality record are available.

The maintenance is essentially improved by the use of a central bearing and special sealing (registration to patent). Since there is no necessary adjustment of the transducers, it's easy to handle. The choice of pipe guidance rings should change along with production. The manual work involved is not very complicated , and is part of the usual work during the extrusion set up procedure.

2.1 Immersion Scanner for pressure calibration

With regards to Extrusion pressure calibration, the scanner can be mounted by a flanged connector within the calibration sleeve and is further also flanged to the first cooling bath. During a period of production, those scanners have proved their reliability.

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Rolf Diederichs 18.Dec. 1995, info@ndt.net

/DB:Article /AU:Diederichs_R /IN:NDTnet /CN:DE /CT:UT /CT:thickness /CT:process /CT:plastic /ED:1996-01