where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

develops and manufactures cutting edge Portable Digital Radiography X-ray Inspection Systems.

Technical Discussions
Eli Brosh
Eli Brosh
09:43 Mar-23-2007
ECT-limiting frequencey for cylinder and tube

In Eddy current testing, the analysis of impedance diagrams is simplified by use of normalized frequency. That is, by using a ratio of the actual frequency used and the "limiting frequency" fg.
In the ASNT handbook, I found the following formulas for fg (in non-ferromagnetic material):
1. for cylinder in an encircling coil: fg=a/(sigma*D^2)
2. for tube in an encircling coil: fg=a/(sigma*D*W)

Where a is a constant whose value depends on the units used, sigma is the conductivity, D is the diameter of the cylinder or the outer diameter of the tube and W is the tube wall thickness.

Strangely, these two expressions do not coincide when W=D/2, that is when the tube becomes a full cylinder.
Have I missed something here /
Does formula 2 have a limited range of application so that it does apply when W=D/2 ?



Product Spotlight

Swift & Scorpion2 - a state-of-the-art remote-control ultrasonic crawler

The Swift and Scorpion2 dry-coupled, remote-access ultrasonic crawler bring major efficiency and d
ata improvements to tank shell inspections and other structures such as vessels and offshore installations.

Wireless TOFD scanner

Quick, accurate and highly reproducible welds testing. The System operates wirelessly and is compat
ible with any type of Windows based Laptop, Desktop or Tablet.

ISAFE3 Intrinsically Safe Sensor System

ISAFE3 intrinsically safe sensor system of Vallen Systeme is especially targeted at the petrochemica
l - as well as oil and gas transportation industry. The sensor system is designed for permanent monitoring or periodic inspection tasks. Sensors are available for different AE-frequency ranges optimized for corrosion and fatigue crack detection and other applications. The ISAFE 3 sensor system consists of an AE-sensor (model ISAS3) certified according to ATEX/IEC for installation in zone 0, gas group IIC, IP68, 20 to +60 °C, and a signal isolator (model SISO3) certified for installation in zone 2. An ISAS3 sensor can be mounted in atmosphere or submerged, e.g. in water or crude oil. It is supported by mounting tools for temporary (magnets) or permanent (welded) installation. ISAFE3 supports automatic sensor coupling test and can be used with any AE signal processor supporting 28V supply at 90 mA peak, e.g. Vallen Systeme ASIP-2/A.

Conformable wedge transducer

The conformability is obtained with a flexible membrane filled with water between the transducer and
the inspected component. The coupling between the membrane and the component requires a small quantity of water or couplant. The conformable wedge combines the acoustic performance of immersion technique with good coupling and low attenuation.

We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
this is debug window