Ultraschall-Prüfköpfe für 650 °C Dauertemperatur / Ultrasound Transducers for 650 Centigrade Continuous Application

Ultrasonic sensors together with a fast data acquisition system have been used to monitor the barrel thickness and barrel/screw separation during low-density polyethylene as well as high-density polyethylene extrusion in 30 mm and 50 mm twin-screw extruders. The sensors include sol–gel sprayed high temperature (HT) piezoelectric thick ceramic film ultrasonic transducers (UTs), stand-alone HTUTs and air-cooled buffer rod type sensors consisting of a room temperature UT and a non-clad or clad buffer rod to which the room temperature UT is attached. The installation and use of these sensors are non-intrusive to the extruder and non-destructive to the polymers being processed. This study has demonstrated the capability of appropriately designed ultrasonic sensors in monitoring the barrel and screw integrity at the melting, mixing and pumping zones of the extruder via barrel or flange. The merits and limitations of these sensors are discussed. The measurement speed and analysis of the sensitivity for quantitative wear measurements are also presented.

Section: Sensors and Data Acquisition Systemmentioning

confidence: 99%

Real-time monitoring of barrel thickness and barrel/screw separation using ultrasound

Jen¹,

Zun²,

Kobayashi³

2005

“…Furthermore, the problem of bonding or coupling of these transducers with target structures or materials often introduces formidable difficulties. Three different methods of coupling at high temperatures are known [7]: dry coupling, fluid coupling and solid coupling. Dry coupling requires coupling pressure even for highly polished surfaces, while liquid couplers, including glass solders, are unstable due to their tendency to dry out, evaporate, solidify or become chemically reactive when exposed to high temperatures [6].…”

Section: Introductionmentioning

confidence: 99%

Hot target inspection using a welded fibre acoustic wave piezoelectric sensor and a laser-ultrasonic mirror scanner

Chia

Lee²,

Shin

2009

The direct attachment of piezoelectric transducers onto hot targets raises formidable challenges as piezoelectric transducers lose their piezoelectric characteristics at elevated temperatures or debond due to thermal expansion coefficient mismatches. We developed a welded fibre acoustic-wave PZT (FAWPZT) sensor to alleviate these temperature limitations. One end of the FAWPZT sensor, made from a stainless steel fibre, was welded onto a stainless steel target plate and the other end was bonded to a PZT sensor. An ultrasonic wave propagation imaging (UWPI) system consists of a laser mirror scanner and a Q-switched pulsed laser (QPL) acting as a non-contact ultrasonic generator was then used to scan a hot target surface with an artificial 2 mm-sized open crack. The result was presented in the form of an ultrasonic wave propagation movie. The damage was detected as a wavefield scattering from the damaged location and its size was evaluated from the plot of amplitude distribution along the propagating wavefront. Sensor performance was briefly discussed and the results confirmed that a FAWPZT sensor combined with a UWPI system has good potential for implementation in hot target integrated structural health management.

“…Because manufacturing processes are usually carried out at elevated temperatures, these UTs must also function at the required temperature. Various efforts have been devoted to the development of high temperature (HT) piezoelectric UTs [3][4][5][6][7][8][9][10][11]. Commercially, several HTUTs are also supplied by several companies, such as Etalon (Lizton, IN, www.etaloninc.com), Panametrics (Waltham, MA, www.panametrics.com), RTD (Rotterdam), Ultran (Boalsburg, PA, www.ultranlabs.com), Ishikawajima Inspection and Instrumentation Co. Ltd (IIICL, Tokyo) [7] etc.…”

Section: Introductionmentioning

confidence: 99%

“…Most of these HTUTs use buffer rods (delay line) to facilitate the fabrication or HT measurements for thin samples and increase the bandwidth. The desired characteristics of HTUTs are summarized in table 1, and can also be found in [3][4][5][8][9][10][11]. 3 Corresponding author.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic probes for high temperature immersion measurements

Rehman

Jen

Ihara

2001

Ultrasonic probes for high temperature measurements in immersion are presented. These probes consist of piezoelectric transducers and buffer rods, and may be operated in the pulse echo mode. The probes can operate to temperatures as high as 215 • C without requiring a cooling system. For imaging purposes, one end of the clad buffer rod is machined into a semi-spherical concave shape, of which the purpose is to focus the ultrasound. The operating frequency is between 5 and 9 MHz. Ultrasonic images, produced using a mechanical raster scan with the probes fully immersed in silicone oil at elevated temperatures, are presented. The importance of the signal-to-noise ratio in the pulse-echo measurement is discussed.