Other industries

Detection of imperfections on internal surface of super-duplex stainless steel tubes designated for oil and gas exploration by means of eddy current method

The SAF 2507 tubes made of super-duplex stainless steel have excellent resistance to various types of corrosion (pitting, crevice, fatigue, stress corrosion cracking) in highly corrosive environments containing chlorides such as sea water. These tubes are used for subsea oil and gas extraction as high pressure hydraulic fluid tubes in umbilicals. The aim was to design a reliable inspection system that would be able to detect imperfections in hot finished tubes already in production. The undesirable defects include non-metallic inclusions in the form of glass which is used as a lubricant during pressing. Insufficient removal of glass leads to the formation of hollows which can create long longitudinal defects at final cold processing.  It was designed rotary probe which is able to reliably detect imperfections on the internal surface of the tube.

                 

Type of imperfection

Eddy current response

Hollow

 

Corrugation

 

Hollow

 

Glass

 

Lift -off

 

Structure noise