Forum Technical Discussions      Re: Urgent- ToFD for Steam Reformer Tube Posted by: Ed T. , E-mail: Address, on December 02, 2008 at 19:53 : In Reply to: Re: Urgent- ToFD for Steam Reformer Tube posted by : Michel Couture , E-mail: Address, on November 30, 2008 at 20:10 : ----------- Start Original Message ----------- : Abi, : The frequency you are using is too high. ASTM A388 para 8.2.1 states that the prefered frequency for coarse grain austenitic materials is 1 MHz and that in many instances it may be necessary to use a frequency of 0.4 MHz. I know that ASTM A388 is for Ultrasonic Examination of Heavy Steel Forgings, but the reason for freqyency selection doesn't change. You are dealing with a very coarse grain structure and you need to lower your frequency.. : Hope this will help. : Cheerio's : Michel : : Dear Gentlemen, : : Does anyone ever involve in research of ToFD for Cast austenitic stainless steel used as ammonia reformer tube? I tried to detect artificial defect in IN 519 material, but I can not distinguish the backwall signal. Can anyone explain why and what should I do to detect the defect in this material by using ToFD? As FYI, I used 2.25 MHz ToFD transducer. Is there any commercial ToFD transducer with frequency below 2.25 MHz? : : Please help me... : : Sincerely Yours, : : Abi ------------ End Original Message ------------ Michel is correct. You need to use a 1.0 MHz. Ducer. But it also needs to be a dual focused probe focused for the thickness you are examining with a refracted longitudinal wave mode.. But it can be done. I would also recomend the use of a UT scope with a strong pulser. That material is tough and some of the grains can be as big as your calibraton reflectors. Follow Ups: Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : : Abi, : : The frequency you are using is too high. ASTM A388 para 8.2.1 states that the prefered frequency for coarse grain austenitic materials is 1 MHz and that in many instances it may be necessary to use a frequency of 0.4 MHz. I know that ASTM A388 is for Ultrasonic Examination of Heavy Steel Forgings, but the reason for freqyency selection doesn't change. You are dealing with a very coarse grain structure and you need to lower your frequency.. : : Hope this will help. : : Cheerio's : : Michel : : : Dear Gentlemen, : : : Does anyone ever involve in research of ToFD for Cast austenitic stainless steel used as ammonia reformer tube? I tried to detect artificial defect in IN 519 material, but I can not distinguish the backwall signal. Can anyone explain why and what should I do to detect the defect in this material by using ToFD? As FYI, I used 2.25 MHz ToFD transducer. Is there any commercial ToFD transducer with frequency below 2.25 MHz? : : : Please help me... : : : Sincerely Yours, : : : Abi : Michel is correct. You need to use a 1.0 MHz. Ducer. But it also needs to be a dual focused probe focused for the thickness you are examining with a refracted longitudinal wave mode.. : But it can be done. : I would also recomend the use of a UT scope with a strong pulser. That material is tough and some of the grains can be as big as your calibraton reflectors. ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help