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Technical Discussions
G.RAVI
G.RAVI
07:44 Mar-21-2011
ULTRASONIC TESTING.

HOW TO SCAN SS316L MATERIAL DIA 16mm 2000mm length.
i seted velocity 5920 4 Mhz compression probe.but i am geting wrong reaedings. what is the problem

 
 Reply 
 
S V Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S V Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
16:21 Mar-21-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

You have not mentioned the purpose of scanning. Is it for discontinuities or for thickness / diameter? You may need to use probes with curved shoes or focused probes in an immersion set up. I will be able to give you more specific advice after getting the actual purpose of scanning from you.

Swamy
Quality and NDT Consultant

 
 Reply 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
16:39 Mar-21-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

Hallo,

as a rule of thumb, the sound velocity of compression waves in austenitic stainless steel, as SS316L, is about 90 to 95 percent of the sound velocity in ferritic carbon steel. So I think that your setting (5920 m/sec) ist wrong, and not the readings.

Regards
Uli Mletzko

 
 Reply 
 
Andrew Cunningham
NDT Inspector
Canada, Joined Jun 2008, 238

Andrew Cunningham

NDT Inspector
Canada,
Joined Jun 2008
238
17:06 Mar-21-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

Measure the thickness with a micrometre and then use the auto-calibration on your ut set to set the correct velocity. The reeding will be correct from there on.

 
 Reply 
 
fernando
fernando
16:33 Mar-24-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

sounds to me like your just setting your velocity and up you go with the inspection.
the velocity for Stainless steel is 5660 and mild steel 5900 m/s. now, this is not a precise number. Calibration is a must. always calibrate instrument to standard before inspection.

happy trails.

 
 Reply 
 
LALIT MOHAN KOTHARI
Consultant, -
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc, India, Joined Jan 2003, 128

LALIT MOHAN KOTHARI

Consultant, -
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc,
India,
Joined Jan 2003
128
09:47 Apr-04-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

G.RAVI,
YOU ARE GETTING WRONG READING BECAUSE WHEN WHEN PIPE IS SCANNED AND SOUND PROPAGATES AROUND THE WALL IN A ZIG-ZAG WAY AND INTERFERENCE BY SHEAR WAVES WHEN COMPRESSION WAVES ARE USED,
SO MOST OF THE TUBULAR SHAPE OBJECT IS DONE WITH SHEAR WAVE.
AND TAKE CARE OF RATIO OF THICKNESS(T) TO DIAMETER(D), IS OVER 0.2 TO 20%,
THE SOUND BEAM WILL NOT TOUCH THE INNER DIAMETER(FOR 40*,60* & 70*)
T/D=0.5(1-SIN D*).
(AS SKIP DISTANCE AND BEAM PATH ,INCREASE COMPARED TO THAT OF FLAT PLATE,DEPENDING ON THE CURVATURE)

IF YOU WANT TO CHECK THICKNESS ALSO THEN TAKE CARE OF SIZE OF PROBE

THANKS & REGARD

LALIT MOHAN KOTHARI

 
 Reply 
 
G.RAVI
G.RAVI
17:04 Apr-05-2011
Re: ULTRASONIC TESTING.
In Reply to S V Swamy at 16:21 Mar-21-2011 .

Dear sir,
the purpose of ut testing is to identify defect and also exact thickness.
that material is ss 316 dia 16 mm 2000mm length. half in the sea water.
it was in DUBAI'S I MEAN WORLDS FAMOUS AQUA VENTURE PARK THE ATLANTIS.
I seted velocity 5660 . 4 Mhz compression probe. i calibrated for 200mm sample ss rod. it was ok . but while scaning the dia 16mmX2000mm length i am geting wrong readings. why it was like that now i am in big trouble please help me out.

 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 524

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
524
18:47 Apr-05-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 17:04 Apr-05-2011 .

There seem to be a few possible cause of error and it is essential that the technique is appropriate.

As noted earlier if the velocity is set for Carbon steel readings will be about 5% high

16mm is quite small, so a curved probe is likely to be needed.

lastly you haven't said if it is tube or bar, since you are measuring thickness I assume it is tube, so you need to think about the thickness and decide if you are using the right probe - if it is thinner than about 1.5mm you may be getting doubling effects.

If you are using a flaw detector it is usually possible to see what is going wrong. If it is just a thickness gauge then it can take a lot of experience to work out why the readings are wrong.

at least in Dubai you have local support from most equipment vendors - talk to the guy you bought the equipment from.

Good luck

Joe

 
 Reply 
 
sadek997
NDT Inspector,
AR, Poland, Joined Feb 2011, 12

sadek997

NDT Inspector,
AR,
Poland,
Joined Feb 2011
12
19:39 Apr-05-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 17:04 Apr-05-2011 .

Dear Mr. Ravi
Hence You have acctually no idea what kind of survey/inspection You want to carry out and You describe the problem in a premature manner I do assume that You have no idea about performing ultrasonic examinations or thickness measurements. Better leave it to a specialist since scanning of non-ferritical materials with ultrasound is far more difficult than it may appear.

If You want to measure thickness of a tube and You have no idea of it's sound velocity/properties simply find a spot on the element, where You can measure the thickness by means of a gauge or a slide caliper. Measure the thickness and set the same on your ultrasonic gauge. Rememer that You need to have a double transducer probe and the dividind sound barrier in the transducer has to be perpendicular to the tube axis (You may have false readings otherwize). If You measured e.g. 10mm (by means of a slide caliper and the ultrasonic gauge indicates the same thickness in this particular spot You will get adequate readings everywhere else). If this dosn't help this means You don't know how to set Your gauge and the cause can be more sofisticated than You think (especially if You have a thickness gauge with a A-scan presentation)
Hope this helps

 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
19:44 Apr-05-2011
Re: ULTRASONIC TESTING.
In Reply to Joe Buckley at 18:47 Apr-05-2011 .

To inspect this material for both thickness and any inclusions you will need to use a fingertip probe which has a probe face of only a few millimeters diameter and are typically accurate down to about 0,7mm. For example a DA212 from GE would suit.
How do you know that you are getting incorrect readings? If you have been able to physically measure the wall thickness, you can use this as a calibration piece. Otherwise, try and get access to a piece of this material.
As Joe says, an ultrasonic unit with an a-scan display would be needed for this examination.

 
 Reply 
 
sudheer jai krishnan
NDT Inspector, -
bluestarindia, India, Joined Mar 2011, 30

sudheer jai krishnan

NDT Inspector, -
bluestarindia,
India,
Joined Mar 2011
30
18:37 Apr-07-2011
Re: ULTRASONIC TESTING.
In Reply to Jon Wallis at 19:44 Apr-05-2011 .

Hi Ravi,

What is the equipment that you are using? Also what is the diameter of the crystal that you are using?

 
 Reply 
 
kamal basha
kamal basha
12:59 Apr-13-2011
Re: ULTRASONIC TESTING.
In Reply to G.RAVI at 07:44 Mar-21-2011 (Opening).

Try 6400 velocity

 
 Reply 
 

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