EMAT - Non-Contact UT Technique – a technique of choice for many applications A non-contact technique, EMAT with a range of diverse advantages that make it a choice of for many applications, including dry inspection capabilities, an imperviousness to surface conditions, and unique wave modes such as shear waves with horizontal polarization (SH waves). Electro-Magnetic Acoustic Transducer (EMAT) is an Ultrasonic Testing (UT) technique that generates sound in the component being inspected rather than the transducer. Because the sound is generated in the part inspected instead of the transducer, as it is completely a non-contact technique, it gives a significant advantages over more conventional piezoelectric transducers; although it also has some weaknesses, which can limit its applications. This technique is capable of generating all wave modes used in ultrasonic testing, including some modes that are very difficult or impractical with conventional transducers. They are used in a wide variety of applications in the O&G and chemical processing industries such as:
INSPECTION OF TUBULARS
IN-SERVICE PIPING
One of the the most common uses of EMAT inspection in the field is the inspection of tubes. Tubes are tested by generating and propagating ultrasonic Lamb waves circumferentially in the tubular. A Lamb wave is a class of plate waves which means that the entire volume of the pipe is filled with ultrasonic energy.
One of the most common uses of a field EMAT inspection device is for volumetric inspection of in-service piping. This technique can be used to examine equipment such as large diameter header piping at high temperature, transmission lines for hazardous wastes, and natural gas distribution lines.
INSPECTION OF VESSELS
REMAINING WALL THICKNESS AT PIPE SUPPORTS
EMAT is proving to be an efficient means of completely inspecting relatively large surface areas of material. The procedure, which has been developed to examine vessels and plates, involves mounting a transmit and a receive EMAT sensor in a fixture, allowing 1 to 2 feet separation. Bulk ultrasonic waves are then generated and transmitted through the material, effecting a volumetric test as the fixture moves across the surface.
A particular application of employing EMATs on tubulars is for the specific determination of pipe wall thickness at the point of contact with a pipe support. Pipes often suffer localized OD corrosion at the support and a determination of remaining wall thickness is extremely difficult using standard techniques. Our recent work has improved on known analysis techniques.
Get to know the dielectric strength of cables by the VLF Very low frequency (VLF) diagnostic testing is the application of an AC sinusoidal waveform, generally applied at 0.1 Hz or lower, to assess the quality of electrical insulation in high capacitive loads, such as cables. A major advantage of VLF is that when comparing the voltage application at power frequency at 50 Hz, there is a 600x lower power and current requirement when testing the same cable at the same voltage level Examine the Dielectric Strength of cables To Sustain its Quality”
RECENT SUCCESS
BENEFITS
WHY VLF?
SGS Pakistan has recently performed testing of VLF at FFC andWind Power Jamphir. SGS not only just tested the dielectric strength but also ensure the quality of their utilities cable and through this testing prevent them from any breakdown due to insulation damage.
• Able to monitor the withstand test. • Able to schedule repair/replacement. • Able to abort the test
VLF test sets are used to field test high capacitance loads like cables and motors/ generators. The lower the frequency of an AC source, the lower the current and power required to apply a voltage to a capacitive load like a cable. At 0.1Hz, it requires 600 times less power to test a cable than at 60 Hz. The HVI VLF instruments permit users to field test long cables and large generators with a portable and affordable test set. A 100 lb VLF instrument can do the job of a multi- ton 60Hz AC test set. Cables should be tested with AC voltage. With the HVI VLF products, it can be done with a practical, economical, and easy to use package.
APPLICATIONS
• Power Cables • Large Rotating Machine
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