Pulsed Eddy-Current (PEC)
Inspection Through Insulation
To be able to assess the condition of pipework and pressure vessels underneath insulation has many advantages for plant operators. It is also possible to accurately monitor corrosion using the same methodology. Developed primarily by Shell Global Solutions in order to serve their own needs, Pulsed Eddy-Current inspection technology is now commercially available by TUV Rheinland who holds an operating licence for PEC inspection equipment. This licence was awarded under our stict staff competence regime and Shell were satisfied with our technical procedures.
Compared with conventional eddy current testing , during a PEC inspection there is no need for direct contact with the object being tested. Measurements can be made through coatings, insulation materials, weather sheeting and even corrosion products.This means that inspections can be carried out through any material that does not conduct electricity. It is a very useful characteristic that also enables high temperature NDT inspections.
TÜV Rheinland Sonovation is part of the TÜV Rheinland Group specialized in providing a complete range of advanced non-destructive testing (NDT) services. In addition to operating a competence center for advanced NDT based in the Netherlands, it maintains branches in the United Kingdom, Belgium, Germany and Saudi Arabia. Acknowledged as leaders in the field, TÜV Rheinland Sonovation invests heavily in R&D and operates an accredited training school for advanced NDT as well as offering its expert services globally.
Benefits of Our Pulsed Eddy-Current Inspection Services at a Glance
Our pulsed eddy-current inspection services offer you:
- No loss of production, as inspection can take place while the inspection object is in service.
- Reduced inspection costs, as insulation material does not need to be removed.
- Speedy inspection, as surfaces do not require any preparation.
- Good reproducibility of PEC readings at the same locations.
- Significantly lowered costs for underwater inspections.
Our Pulsed Eddy-Current Inspection Approach
The PEC instrument probe is placed against the metal weather sheeting (non-ferrous) of the insulation pipe or vessel. The geometry of the test object should be simple. A magnetic field is created by placing an electrical current in the transmitting coil of the probe. This field penetrates through the weather sheeting and magnetizes the pipe wall. The electrical current in the transmission coil is then switched off, causing a sudden drop in the magnetic field. As a result of electromagnetic induction, eddy currents will be generated in the pipe wall. The eddy currents diffuse inwards and decrease in strength. The rate of decrease of the eddy currents is monitored by the PEC probe and is used to determine the wall thickness. The thicker the wall, the longer it takes for the eddy currents to decay to zero.
The PEC wall thickness readings are relative values, showing variations in the wall thickness of the object under inspection. Whilst this is sufficient in many applications, absolute readings can be obtained by wall thickness calibration at a specific point along the object.
Pulsed Eddy-Current Application Range
Our pulsed eddy-current inspection service can be used for:
- Inspection of carbon steel and low-alloy steel.
- Thickness measurements through any non-magnetic material up to 200 mm thick.
- Inspections at a temperature range from -100°C to 550°C (-150°F to 1000°F).
- In-service inspections.
- Heavily corroded equipment.
- Concrete fire proofing.
- Corrosion monitoring thanks to very good reproducibility of PEC inspection readings at the same locations.
- Remotely operated vehicles (ROV´s).