The Implementation of the New Standard EN ISO for Ultrasonic Phased-Array Systems at the Manufacturer

Transcription

1 19 th World Conference on Non-Destructive Testing 2016 The Implementation of the New Standard EN ISO for Ultrasonic Phased-Array Systems at the Manufacturer Johannes BUECHLER 1, Udo SCHLENGERMANN 2 1 GE Sensing & Inspection Technologies GmbH, Hürth, Germany 2 Udo Schlengermann, Germany Contact johannes.buechler@ge.com; udo.schlengermann@t-online.de Abstract The conformity of the ultrasonic testing system to a global standard is getting required by the users to ensure the proper performance of the equipment as the basis for reliable test results. It is the intention of the new standard EN ISO for ultrasonic phased array systems, which is published in 2015, to provide the measurement procedures and the acceptance criteria for the declaration of conformity. The standard will be used to verify the properties of the array instrument, of the array probe and of the combined system. Accordingly the standard is structured into three parts for the characterisation of the phased-array test equipment covering the frequency range from 0,5 MHz to 10 MHz: Part 1: Instruments Part 2: Probes Part 3: Combined systems Part 1 and Part 3 are divided into two groups of tests separating the measurements to be done once and those to be performed periodically. The required measurements for the declaration of conformity of the instrument and probe are extensive and time consuming due to the high number of channels and array elements. A time and cost effective test can only be done using an automated measuring system. The implementation of such a mobile, automated measuring system at the manufacturer will be presented which complies with the stipulations of the standard EN ISO With the use of the automated test system and a related test procedure following Part 1 and Part 2 of the standard, the specified acceptance criteria in the manufacturing process and also within the lifetime of the array instrument and probe ensure that the operator is using test equipment with verified properties. Part 3 of the standard gives guidance for the operator to check the combined system, instrument, probe and cables connected, for proper performance during his work. Additional tests for a particular application have to be defined by the person responsible for the procedure of the application. Keywords: phased-array ultrasonic testing (PAUT), phased-array test equipment, standardization, automated measuring system License: 1 More info about this article:

2 1. Introduction The established use of ultrasonic phased-array technology with its equipment for industrial applications required the need for standards in this area. These can be sorted into three categories: Terminology, Test equipment, Applications. Based on the existing European Standard EN 12668:2010 for the characterization and verification of ultrasonic test equipment for conventional testing the new standard EN ISO for the characterization and verification of ultrasonic phased-array equipment was created, which is also divided into the three parts: Part 1: Instruments, Part 2: Probes, Part 3: Complete systems. Part 1 and 3 are released as EN ISO and EN ISO and part 2 as EN , all are in accordance with European Standard EN 16018:2011 which defines the phasedarray terminology. 2. The standard for phased-array equipment 2.1 Instruments, EN ISO Part 1 defines the methods for the measurements and verification of the phased-array instrument within the frequency range of 0,5 MHz to 10 MHz including the acceptance criteria. Parts of this test can be also used for phased-array instruments in automated test systems, but then other tests may be needed to ensure a satisfying operation. The acceptance criteria for the measurements may be modified by agreement of the parties involved. The standard defines two groups of measurements: Group 1: tests to be performed by the manufacturer on a representative sample; Group 2: tests to be performed on every instrument, prior to supply, after repair or every twelve months by the manufacturer or a test laboratory. Table 1: Instrument tests to be performed Group 1 (once by manufacturer) Battery operated instrument Stability Display Operating time Stability against voltage variations After warm-up Against temperature Time base error Highest digitised frequency 2

3 Transmitter Receiver Monitor gate Beam forming Screen refresh rate for A-scan presentation Pulse repetition frequency Output impedance Time delay resolution Cross-talk Dead time after transmitter pulse Dynamic range and maximum input voltage Input impedance Time corrected gain (TCG) Temporal resolution Time delay resolution Linearity of vertical display over the extreme frequency ranges Linearity of monitor gate amplitude Time-of-flight of monitor gate Impedance of analogue output Linearity of analogue output Influence of the signal position within the gate Rise time, fall time and hold time of analogue output Summation of 4 signals Group 2 (on each instrument and every 12 months) Instrument Transmitter Receiver Visual inspection Amplitude Rise time Duration (width) Linearity of time delays Frequency response Channel gain variation Equivalent input noise Gain linearity Linearity of vertical display Linearity of time delays 3

4 2.2 Probes, EN Part 2 defines the measurements and verifications of the characteristics for linear phasedarray probes used in contact or in immersion technique within a frequency range from 0,5 MHz to 10 MHz including the acceptance criteria which have to be used to issue a declaration of conformity for the probe after manufacturing. This standard is published as EN and the request for getting it into an ISO standard is started as ISO With this step the new revision will incorporate 2D arrays. When this is completed it will be aligned with the EN ISO standard family. Table 2: Probe tests to be performed Probe Each element Two elements Visual inspection Frequency Bandwidth Pulse duration Relative sensitivity variation Probe sensitivity Inter-element cross-talk 2.3 Combined systems, EN ISO Part 3 is used for phased-array systems with linear phased-array probes in contact or immersion testing within the frequency range from 0,5 MHz to 10 MHz. It specifies the measurement procedures and acceptance criteria for the complete system consisting of the instrument, probe and probe cable prior to the application test to ensure correct operation. The measurement methods can be utilized on site or on shop floor, they are not intended to prove the suitability of the system for particular applications. The measurements are also, as in Part 1, divided into two groups, Group 1 for the test which have to be done once and Group 2 tests which have to performed periodically if the combined system was not changed. The measurements of Group 1 have to be documented in the system record sheet and this will be updated during the Group 2 tests. This part is not intended to be used for encircling arrays, series of apertures having different number of elements, different settings for transmitting and receiving and post processing signals going beyond delay law calculations. 4

5 Table 3: System tests to be performed Group 1 (once) Group 2 (workshop or on site, periodically) Elements and channels Beam characterisation Imaging Channel assignment Relative sensitivity of elements Absence of saturation Probe index point Angle(s) of refraction Sensitivity along the beam axis Beam dimensions Squint angle Grating lobes (recommended) Reflector positioning -6dB spot size Amplitude comparison Visual inspection of equipment Relative sensitivity of elements Linearity of the amplification system Absolute sensitivity of virtual probes Relative sensitivity of virtual probes Probe index points Angle(s) of refraction Squint angle 3. The implementation of the standard for phased-array instruments The high number of channels of the phased-array instrument needs a huge amount of measurements which will be very time consuming in case of a manual measurement. Considering the manufacturer measurements required for each instrument and the periodical annual measurements defined in group 2 of EN ISO they can only be effectively performed by an automated test system. The used test system consists of a signal generator, attenuator, oscilloscope and a control PC which drives the measurement devices and loads the required data sets for the individual measurements into the instrument. The control software runs automatically all tests and then the PC has to store all the measured data to generate finally the declaration of conformity if all measurement results are within the required tolerances. For an instrument like the USM Vision which has 16 channels with a multiplexer to 128 channels about 500 measurements for group 1 tests and 2000 for group 2 tests need to be performed. The high number of measurements in group 2 is driven by the gain linearity test across the total gain range for each channel which is not multiplexed. 5

6 The number of measurements increases significantly with the number of channels if they are not multiplexed. The USIP xx testing machine is a scalable instrument platform designed to provide high productivity and probability of detection for in-line ultrasonic testing, which requires many high element probes [5]. The instrument is based on 64- channel modules which are plugged into one rack, which can contain up to 12 modules allowing 768 channels. To test the 64-channel module 6000 measurements are needed to perform the group 2 tests. For many automated testing machine applications multiple racks with 768 channels are used. As an example, a full parallel 1400 channel instrument supporting multiple phasedarray probes would need instrument measurements for the group 2 tests. Before putting the testing machine into operation reference measurements will be performed to define the required parameters of the instrument. The reference measurement values will then be taken to define the tolerances for the periodical in-service tests. As an example the measurement values of the transmitter characteristics will include the testing machine configuration, like probe adapters. The automated test system allows an on-site instrument verification, see Fig.1. Fig. 1: Automated test system (red box) for on-site instrument verification 6

7 4. Conclusion To make the measurement effort effective the measurements are categorized into groups and done at different time intervals, see Table 4. Table 4: Standards and their measurement intervals I stru e ts Pro es Co i ed Syste s EN ISO - EN - EN ISO - EN ISO - Group : o e Group : periodi ally after a ufa turi g Group : o e Group : periodi ally The high number of measurements to qualify phased-array instruments and probes can only be efficiently performed using automated test systems driving and measuring the device under test and storing all data for traceability. For phased-array testing machines using a very high number of channels even with an automated test system the measurements to be performed according to the Part 1 Group 2 tests will be time consuming which will lead to system down time in case of requalification. Therefore it is necessary to modify or reduce the required measurements in agreement with the customer, and to plan additional application tests to ensure satisfying system performance. References 1. EN 16018, Non-destructive testing - Terminology - Terms used in ultrasonic testing with phased arrays; Trilingual version 2. EN ISO , Characterization and verification of ultrasonic phased-array equipment - Part 1: Instruments 3. EN , Characterization and verification of ultrasonic phased-array equipment - Part 2: Probes 4. EN ISO , Characterization and verification of ultrasonic phased-array equipment - Part 3: Combined systems 5. Buechler, Johannes; Steinhoff, Norbert: High-End Ultrasonic Phased-Array System for Automatic Inspections; 18th World Conference on Nondestructive Testing, 2012, Durban 7