·Table of Contents
·Methods and Instrumentation
The State of the Art of Weld Seam Inspection on Pipes by Automated Ultrasonic System Using Special Composite TransducersEng. Edson Vasques Moreira
Material Engineer, CONFAB INDUSTRIAL S.A. Brazil,
NDT, Calibration and Qualification Supervisor
Eng. Luiz Francisco Martins de Oliveira
Mechanical Engineer, CONFAB INDUSTRIAL S.A. Brazil, Quality Control Manager
Eng. Sérgio Ricardo Pinto Ferreira
Mechanical Engineer, CONFAB INDUSTRIAL S.A. Brazil, Industrial Manager
|Fig 1: Ultrasonic System Position on the Pipe Mill|
The mill, where this system was installed is a pipe manufacturing plant, UOE process, that means U press, O press and cold Expansion. This plant has a high productivity and uses heat rolling plates. After forming, these pipes are longitudinally welded by submerged arc welding in accordance with mainly, API 5L specification and the other special requirements. Please see Figure 1, below.
This plant manufactures pipes with maximum individuals length of 12,4 m or jointers up to 24,0 m. The diameter range is from 12,750" to 48" and the thickness range is from 0,250' to 1,250". The ultrasonic system that we are explaining is located immediately after the cold expansion and hydrostatic testing, that corresponds to the final ultrasonic inspection of the weld seam on the pipe.
|Method of inspection||Pulse-echo and through transmission.|
|Speed||Maximum 25 m/min.|
|Probes||Krautkramer, 4MHz, crystal 9x8 mm.|
|Apparatus||Krautkramer USPC 2100. 02 with 8 channels e 01 with 04 channels.|
|Gates||Interface, Indications e Coupling.|
|Scanning||Longitudinal weld seam.|
|Delectability||Notches N5 e drilled holes 1,6 mm.|
|Results||Printed and micro computer.|
|Others functions||Alarm sonorous and visual and paint gun.|
|Table 1: Technical Characteristics of system|
4.1 Ultrasonic equipment.
The ultrasonic system for automatic inspection has new conception and technical characteristics that result in a good performance, it's working with speeds of 25 m/min and 14 probes. The USPC2100 can work with 2500 Hz of pulse repetition frequency per channel. This equipment works with multiplex or in parallel mode. Please see bellow the equipment view on the Figure 2 and 3. When it is necessary more than 08 channels, for the synchronization, one equipment works like MASTER and the others work like SLAVE.
|Fig 2a:||Fig 2b:||Fig 3a:||
Fig 2: Ultrasonic equipment USPC 2100 - Gates and Strip options
||Fig 3: Ultrasonic equipment USPC 2100 - System and Measurement options
Probes are used immersion with crystals of Barium Titanate with a frequency of 4MHz, dimensions 8x9 mm. The refraction angles normally used are 70, 60 and 45 degree, also all of them work with shoes that guaranty the perfect coupling to several diameters of the pipe. These probes have a divergence angle between 15 to 20 degree and this allows to detect holes with diameters of 1,6 mm and longitudinal and transversal, inside and outside notches N5. Nowadays we are testing a new type of probe made with crystal of composite. It presents advantages over the traditionally used up now. Basically speaking, these composite probes can help the inspection with the echoes and noise reduction without lose the sensibility and the resolution during the inspection. The quantity of gain necessary to calibration using composite probes is 6 dB less than a Barium Titanate probe. Please see the comparison of screens on the Figure 4, when we do the calibration using a drilled hole 1,6 mm of diameter) at 100% of the screen high. The pipe dimension is 20" x 0,875".
|Fig4a: W70Z4NE - Composite||
Fig4b: W70Z4N - Barium Titanate
Fig 4: Comparative echograms between transducers W70Z4N e W70Z4NE|
A reference standard is used to calibrate the system using a pipe with the same dimensions that the pipe to be inspected and machining artificial defects, outside and inside notches N5 (longitudinal and transversal) and drilled holes with diameter of 1/16 inches.
|Fig 5: Reference Standard||Fig 6: Basic Probes Configuration|
|Fig 7: Probes coupling automation|
|Where:||V maximum||= Maximum speed of inspection, in m/min..|
|RPFHz||= Pulse Repetition Frequency, in Hz.|
Nondestructive inspection system must demonstrate consistent detection of defects and it is important to measure the defect detection performance to an inspection's reliability. Using the fixed parameters like pitch, pulse gap, speed, PRF, etc., after the system is calibrated, the reference standard shall be passed through a minimum of 10 times and when the holes and notches passes through the probe the system has detect all the time. The dynamic run, with same speed of pipe production revels the inspection system's performance for detection of artificial defects. As a minimum, the signal amplitude achieved on the dynamic run shall exceed the alarm threshold setting used for each applicable reference notches and holes. Inspection system which not demonstrate repeatable detection of reference standard shall have similar poor performance in detecting natural imperfections, and in such cases, adjustments to the inspection parameters or equipment should be made to assure repetitiveness defect detection. Other important factors is that the personnel that are responsible for the operation of equipment are qualified and understand the inspection process also work with a qualified procedure by a Level III inspector.
This new automatic inspection system installed on CONFAB Industrial S.A. can attend the API Specification 5L and also several supplementary requirements. The probes arrangements available in this system, data record and a set of others resources permit to inspect with accuracy technique, providing a excellent assurance, productivity, traceability and reliability.
|© AIPnD , created by NDT.net|||Home| |Top||