Can anyone explain me about elecromagnetic inspection
When i calibrate EMI unit for inspecting seamless pipe with 10% notches both ID & OD
for longitudinal & transverse orientations, all peak signals approxcimate 50% FSH.Thus running for inspection, the unit catch 21% fsh on the chart but i interested to evaluate the indication. During evaluation proven that indication from OD Pitting with depth 12% of nominal thickness. My question are:
~Why indication appears on ID?
~Why indication of OD pitting less than Notches, whereas deeper than ??
22:42 Jun-02-2009 Re: EMI Flaw Report In Reply to kusnadie at 11:24 Jun-01-2009 (Opening).
it looks like you operating a four function emi unit.
Separation of flaw for od or id location is based on some unit about the frequence of the flaw signal, but does not worked everytime correctly.
Anyway round bottom pitting on the external surface hardly produce a fluxleakage.Normally you see that better on the longitudinal system.
For used pipe normally a 1/16" drilled through hole is used.You did not mention what kind of pipe or which spec you used.
A notch produce is higher flux leakage and therefor mechical defects like couges ,cut etc will overn evaluted and pitting under estimated.
A good indication is the frequency of your flaw indication.
Make up ypur mind ,you using 1/16" holes or notches or both ?
Or using the notches for the longitudinal system and holes for the transversal system.
On standard unit there should be 8 holes to check trail and lead sensors in one go.
As i sayes on the first replay OD pitting have hardly a flux leakage and therefore a smaller amplitude.
OD/ID flaw separation on your unit seems to be by frequency of the flaw response.
Normally a 10% notch is used for new casing acc API Standard API5CT.On new casing you looking for defeccts from the manufacturing process lile seams,overlap etc.
On used pipe you looking mainly for mechanical defects/flaws and corrossion.The flaw response from this defects are differrent and you need to establish your on reference level according to the defect to be found.
If you inspecting used casing you should use the API RP 5C1.