where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
567 views
Technical Discussions
Terry White
Terry White
04:29 Dec-17-2002
U/T rep rate

We test nickel alloy billet material using basic pulse echo techniques. our method spec calls for a minimum pulse repetition rate of 500PPS. We often experience "wraparound" at this rate and have to lower the rep rate to eliminate the unwanted signals. My question is, why is it so important to maintain that rep rate? What harm could dropping it to 450 - 400 PPS do? Max surface scanning speed is 10 lin. inches per/sec. Transducer is 10 or 5MHz. Beamwidth as measured at .150" metal travel on a #1 FBH cal block is @ .040".


 
 Reply 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 182

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
182
06:46 Dec-17-2002
Re: U/T rep rate
reply:
Hello Terry,

If your scanning speed v is 10"/s and your beam width b is only 0.040", i.e. per shot you cover only 0,040", you need a pulse repetition rate for complete coverage of
frep = v/b.
For your example that means frep = (10"/0.04"s)=250Hz at least.
If you want a factor n for redundancy, i.e. n pulses per beam diameter b, the equation goes to
frep = n v/b.
In your case n=2 means frep = 2 10"/.040"s) = 500 Hz.

You are correct, that this repetition frequency may be too high for low attenuating materials as nickel based alloys are.
The only solution then is to look for the maximum repetition rate fmax you can work with (static), and for scanning to lower the scanning speed until you get full coverage including a safety factor n:
vmax = (b fmax/n)
If you get fmax = 50 Hz, with n = 2 you will get the maximum allowable scanning speed vmax = (0.04" 50/2s)= = 1"/s only.
May be, for lower repetition rates you need a digital ultrasonic instrument, because they have separate screen refreshing rates independent from pulse repetion frequency, whereas with analog instruments the screen refreshing rate is the same as the pulse repetition frequency and for low rates you will not see a constant screen display.

Kind regards
Udo Schlengermann
Agfa NDT GmbH, Huerth, Germany
+++

: We test nickel alloy billet material using basic pulse echo techniques. our method spec calls for a minimum pulse repetition rate of 500PPS. We often experience "wraparound" at this rate and have to lower the rep rate to eliminate the unwanted signals. My question is, why is it so important to maintain that rep rate? What harm could dropping it to 450 - 400 PPS do? Max surface scanning speed is 10 lin. inches per/sec. Transducer is 10 or 5MHz. Beamwidth as measured at .150" metal travel on a #1 FBH cal block is @ .040".
.



 
 Reply 
 

Product Spotlight

NDTkit RT

NDTkit RT, TESTIA's Digital Radiography software The NDTkit product line software for X-ray analysi
...
s. NDTkit RT is a software benefiting from the Ultis kernel which is dedicated to radiographic image analysis. It offers a set of tools and filtering processes to assist RT operators in finding relevant flaws.
>

A1525 SOLO

A1525 Solo – the most compact and affordable TMF unit with two phased array transducers and 3D v
...
isualization and analysis software in standard delivery set. A compact, ergonomic and easy to handheld Phased Array unit based on Total Focusing Method for easy-going imaging of inspection objects with two-dimensional and three-dimensional visualization and evaluation of inspection results.
>

TraiNDE UT

TraiNDE UT is a virtual tool associated with a signal database which simulates real inspection con
...
ditions for numerous applications (Type A/V1 block, DAC block, welds and plates).
>

SITEX CPSERIES

Teledyne ICM’s CPSERIES has been designed with a view to revolutionizing the handling and perfor
...
mances of portable X-Ray sets. Despite having managed to halve the weight of similar portable X-Ray generators available on the market (while continuing to provide the same power output), the SITEX CPSERIES generators feature a shutter, a laser pointer, a beryllium window, an aluminum filter and two integrated diaphragms (customized sizes are available upon request). Without compromising the robustness and reliability for which ICM products are renowned, the small size and light weight of the SITEX CPSERIES will radically change the way that you perform your RT inspections. And you will see a positive impact in terms of both quality and return on investment (ROI).
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window