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TOFD – 厚壁壓力容器焊接檢測超聲成像計算機技術

 

TOFD - the emerging ultrasonic computerized
technique, for heavy wall Pressure Vessel welds examination
TOFD –
厚壁壓力容器焊接檢測超聲成像計算機技術 (全文下載)

F. Betti, A. Guidi, B. Raffarta - NUM PIGNONE - Massa (Italy)
G.Nardoni, P. Nardoni, D. Nardoni - I&T Brescia (Italy)
L. Nottingham - Structural Integrity - U.S.A

 
Index
  • Abstract
  • Fundamentals of the TOFD technique
  • TOFD norms
  • TOFD Applications
  • Physical principle of TOFD
  • Configuration of system
  • Scanning plan
  • Scanning direction
  • Real time acquisition and records
  • Image evaluation
  • Experiences on examination of welds
  • Conclusions
  • Bibliography
Abstract
The paper presents TOFD, the Time of Flight Diffraction Technique, currently the most promising ultrasonic technique for examination of heavy wall thickness welds on Pressure Vessels TOFD, is a computerized ultrasonic system, able to scan, store, and evaluate indications in terms of height (through thickness weld), length, position, with a degree of accuracy never achieved with other ultrasonic techniques. A record of examined sections is available in unprocessed form on floppy disk or CD and readable in Word for Windows 95. The ASME Code, with Code Case no. 2235 has accepted this method in lieu of radiography examination for thicknesses over 4 " (1). Experiences on 75 mm up to 300 mm thick welds of 2.5 / 3 % Q 1 Mo, 0.25 V and Carbon steel are discussed. The technique has been applied on longitudinal, circumferential and nozzle-shell/bead welds. Scanning Plan Data and its validation are reported with used test blocks. Cladded layers in TOFD images are presented. Based on experience to date, prospects for this new technique are of great interest.

New Non-destructive Examination
(TOFD SYSTEM)

 

 

 

HIGHLY RELIABLE UT TECHNIQUE-----TOFD UT SYSTEM

All the butt welds of high pressure vessels manufactured in accordance with ASME Sect. VIII.DIV.2 should be inspected by using RT for quality assurance. But recent ASME Code Case 2235 permits automatic UT in lieu of RT. Kobe Steel has developed the new automatic UT technique using TOFD (Time of Flight Diffraction) method and has been using for inspection of welds of heavy wall pressure vessels in lieu of RT.

<Features of TOFD>

  1. High Probability of Flaw Detection
  2. High Accuracy of Flaw Location Measurement
  3. High Accuracy of Flaw Sizing in Length
  4. Weld Integrity to be observed on CRT in Real Time as probes scan
  5. All inspection Data to be Digitised and Stored so that the Data can be Recalled and Processed for In-Service Inspection

<What is TOFD?>

The basic configuration for TOFD (Time Of Flight Diffraction) technique consists of a separate ultrasonic transmitter and receiver. After emission of a compressional wave from a transmitter, the first signal to arrive at the receiver is lateral wave through upper surface. In the absence of defects the second signal to arrive at the receiver is the backwall echo. The diffracted signal generated at the upper tip of a defect will arrive before the signal generated at the lower tip of a defect.

With a time of flight of each flight path, the ultrasonic velocity and the spatial relationships of the two probes, location and height of defects can be very accurately calculated.

Gray scale imaging techniques are applied to the RF(AC) signal phases and enable weld integrity to be observed in real time. The defects are shown like as shell pattern on CRT. A-scan signals are stored in the memory together with location signals.

 

 

TOFD System

TOFD system consists of computerized UT detector, transmitter, receiver, pream-plifier, encoder and cables.

TOFD system is small and light and is portable and accessible to inspection position.

 

Scanning and display on CRT

D-Scan

D-scan is non parallel scanning placing weldment at the center of the two probes.

Signals from the upper and lower tips of a defect are displayed on gray scale.

D-scan and length and height of a defect can be accurately measured. D-scan is the most popular scanning procedure for weldment.

 

 

 

 SubMenu  

 

 

無損高溫TOFD檢測

產品簡介      

Sonovision是堅固、可攜式的超音波檢測系統,能夠同時做多頻道的Time-of-Flight-Diffraction (TOFD) 以及脈沖回波 Pulse Echo (PE) 的腐蝕/侵蝕的內部掃描到大范圍的單一/多軸控制器,包含影像追蹤。本系統與各種的數據收集兼容并且能夠在Windows 95/98/ME/NT/2000/XP離線數據分析軟件內作業。

主要特色
l           膝上型可攜帶的完整廂型系統。 
l           1, 2, 4, 8 16 可轉換頻道 
l           整合成單卡方案包含整個超音波脈器/接收器/digitiser & DSP 
l           實時射頻, A, B, C, D-scan 顯示以及儲存 
l           多頻道, 同步TOFD 以及脈沖回波 Pulse Echo 腐蝕/侵蝕圖像能力 
l           Position stamping from up to 2 encoders 
l           使用影像追蹤技術做腐蝕掃描 
l           完整的表面配置,數據取得, 離線分析以及做報告軟件 
l           Windows 95/98/ME/NT/2000/XP 操作系統 
l           利用daisy-chaining額外的卡最多可擴充到256 頻道·   
l           外部或是內部馬達趨動選項 
l           電池作業時間長達2-4 小時或是利用擴充的電池選項可以延長到6-8小時 
持續的軟硬件更新以及改善
個人計算機規格
 
一般
 
實體
處理器
Pentium Centrino 1.4/1.6GHz
外部體積
310Wx254Dx121Hmm
(12.2"x10.0"x4.7")
內存
256MB DDR(可升級)
重量
6.5公斤(14lb)
硬盤
40GB(可升級)
溫度范圍
0o C50o C
屏幕
14.1"XGA(1024x768)
在白天仍可以清楚看到屏幕的TFT(可升級)
 
 
電力
界面
2xRS232(可以選RS422/RS485),
EPP/ECP parallel,2xUSB, 10/100
以太網絡
 
輸入電壓
100-240VAC(10-20V DC可選)
儲存
1.44MB floppy,
CD-ROM(RW可選)
電池
作業下2-4小時
(外加電池可以擴充到6-8小時)
 
 
 
 
 
 

無損高溫TOFD 檢測

經過過去幾年多次的現場測試經驗,我們有豐富的使用TOFD做高溫檢測的經驗。
TOFD技術,溫度差異的影響可以比較容易量化以及證實。
最初的研發工作是在幾年以前,一個工程師在檢測200度高溫的蒸氣鍋爐時由客戶以及Stoomwezen (荷蘭籍的檢測人員)發展出來,這個技術后來用在設定間隔的的非破壞檢測上。

直到最近在溫度的信度上才有很大的進展。Sonovation 縮短了工作中的焊接檢測(在高過攝氏400度的化學反應槽外殼),一再的證實TOFD偵測技術以及在高達攝氏450度量測缺陷尺寸確實可靠!!

 
 
 
證實可以運用高溫焊接檢測
 Sonovation 一再的在高達攝氏435度的焊接表面完成檢測。TOFD 檢測包含在化學反應器的焊接、連到240公厘到180公厘壁厚的圓頂。 
這個挑戰的復雜度包含了幾何學以及Sonovation團隊在現場所要克服的高溫工作狀況。不斷的密切的與客戶合作、熱情以及專業的Sonovation團隊證實能夠帶給客戶更具創造性的解決方案。
 
Sonovation 主要的客戶范圍
化學、石化、煉油、氣體開采以及生產行業
Sonovation 主要提供的服務
-TOFD ( Time of Flight Diffraction)
-項控數組 Phased Array
-C-scan 腐蝕掃描
-長距離超音波 Long Range UT (腐蝕檢測/掃描)
-管道掃描系統
-脈沖渦電流 (腐蝕監控/檢測)
-
傳統的超音波(焊接檢測)
-MT
-PT
-顧問
特定應用
-復雜幾何
-高溫
-
-
非標準化材料
熱氫害
 
長距離超音波
 



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