| CORROSION |
| CORROSION |
| SLEEVING |
| REMOTE FIELD |
| REMOTE FIELD |
| SLEEVING |
| TANK FLOOR |
| ACFM |
| PIPING |
| CHILLERS |
| TANK FLOOR |
| ACFM |
| CHILLERS |
| PIPING |
Eddy Current
| Magnetec Inspection, Inc. |
| Magnetec Inspection, Inc. |
| ECT |
| ECT |
| THE EDDY CURRENT TECHNIQUE |
It is based on the induction of an electromagnetic field in
the component undergoing inspection. It can be applied
to electrically conducive but non-ferromagnetic materials,
and can detect various forms of internal and external
damage to the object being tested.
the component undergoing inspection. It can be applied
to electrically conducive but non-ferromagnetic materials,
and can detect various forms of internal and external
damage to the object being tested.
It uses a probe with a built-in bobbin coil that induces
eddy currents in adjacent material. Should the probe
encounter flaws as it is pulled through the tube, the eddy
currents are interrupted, causing an impedance change
in the coil. The impedance change is measured and
displayed on a monitor.
eddy currents in adjacent material. Should the probe
encounter flaws as it is pulled through the tube, the eddy
currents are interrupted, causing an impedance change
in the coil. The impedance change is measured and
displayed on a monitor.
Eddy Current testing is very sensitive to most defects that
occur in tubes. It is critical to use correct eddy current
techniques and procedures for conclusive results.
occur in tubes. It is critical to use correct eddy current
techniques and procedures for conclusive results.
| The three primary techniques are differential, absolute, and multi-frequency (SEE BELOW) |
| Differential Method: |
| Absolute Method: |
| Multi-frequency Method: |
The Differential Method uses two coils in one probe to compare adjacent sections of the tube.
When both coils are positioned on sound areas, the signals from both are identical. When one
coil passes over a defect, the instrument compares the differences in the two signals to eval-
uate the defect. This method is very sensitive to defects that cause an abrupt wall section
change.
When both coils are positioned on sound areas, the signals from both are identical. When one
coil passes over a defect, the instrument compares the differences in the two signals to eval-
uate the defect. This method is very sensitive to defects that cause an abrupt wall section
change.
The Absolute Method uses two separate probes, one positioned in a known reference tube, the
second positioned in the tube under examination. The instrument compares the signals from
the two probes to detect and evaluate the defects. This method is sensitive to gradual volu-
metric changes in the tube wall.
second positioned in the tube under examination. The instrument compares the signals from
the two probes to detect and evaluate the defects. This method is sensitive to gradual volu-
metric changes in the tube wall.
The Multi-frequency Method simultaneously conducts multiple differential and absolute tests
with frequency mix techniques. This powerful examination combines the defect detection capa-
bilities of the previous methods into a single, accurate test. It also provides enhanced defect
detection for each type of test through the use of multiple frequencies sensitive to different
types of defects.
with frequency mix techniques. This powerful examination combines the defect detection capa-
bilities of the previous methods into a single, accurate test. It also provides enhanced defect
detection for each type of test through the use of multiple frequencies sensitive to different
types of defects.
| ADVANCED TECHNIQUES USE COMPUTER CONTROLLED INSTRUMENTS |
