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 TÜV Rheinland who holds an operating license for PEC inspection equipment. This license was awarded under our strict 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 testing or offshore well 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.
- Reliable inspection of your offshore well surface casings.
Please feel free to contact us at TÜV Rheinland to learn more about how our Pulsed Eddy-Current inspection services can benefit your company.
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).
- Offshore well inspection.
Offshore Well Inspection Services
Because they are located in a harsh sea and aggressive environment, offshore wells are especially vulnerable to corrosion. More specifically, severe corrosion on a surface casing weakens and hinders it from carrying its design load, increasing the risk for the catastrophic collapse of an offshore well platform.
Corrosion on surface casings of offshore well pipes mostly occurs at the sea level, between the lowest (LAT) and the highest astronomical tides (HAT), where most lateral forces caused by waves and marine currents apply. This area, known as D-annulus, is the space between the two concentric objects of offshore well tubing and its casing into which fluid can flow. Our exclusive TÜV Rheinland Sonovation D-PEC inspection services enable you to monitor corrosion at the D-annulus level of a surface casing without interrupting production.
Exclusive Offshore Well Structural Integrity Inspection
To conduct offshore well inspection, TÜV Rheinland experts insert the Pulsed Eddy-Current probe into the D-annulus gap to detect corrosion on the casing. Measurements are usually taken at sea level, the weakest and most solicited area of an offshore well piping; that is, in the zone between the lowest and highest astronomical tides.
D-PEC is an exclusive non-destructive method which helps you ensure the structural integrity of offshore wells. Furthermore, TÜV Rheinland Sonovation is the only recognized inspection company to hold a worldwide license for this particular inspection method.
Reference Case: Assessment of Offshore Wells, UAE (PDF, 107 KB)