The MsS system uses MsS technology to inspect a structure using ultrasonic guided waves. The MsS System is composed of the MsS Guided Wave equipment, MsS probes, and a laptop computer as shown in the below photo. The operating software in the laptop computer controls the operating parameters of the MsS Equipment and acquires data through a USB port. The MsS equipment generates and delivers tone-burst electric pulses to the MsS probes and detects induced voltage in the MsS probe when the ultrasonic guided wave passes through the probe. The signals received from both directions of the pipe are analyzed and reported with data analysis and reporting software in the laptop computer.
The Magnetostrictive Sensor (MsS) generates and detects ultrasonic guided waves electromagnetically in the material being tested. It utilizes the magnetostrictive effect to generate and detect ultrasonic waves. This effect is the small change in the physical dimensions of ferromagnetic material when an external magnetic field is applied to it. The MsS utilizes the inverse magnetostrictive effect to detect the ultrasonic waves. This effect is the change in the magnetic induction of ferromagnetic material caused by propagating ultrasonic wave. Since the sensor relies on the magnetostrictive effect, it is called a Magnetostrictive Sensor (MsS).
The MsS Probe consists of a ferromagnetic strip and a MsS adapter including a ribbon cable. The ferromagnetic strip is attached to the pipe through dry coupling, shear couplant, or epoxy bonding (refer to Probe Installation for details). The MsS adapter and ribbon cable are laid on the top of ferromagnetic strip. The MsS Equipment applies electric current in the MsS adapter, and the electric current generates a time-varying magnetic field to the ferromagnetic material for generating an ultrasonic wave. The generated ultrasonic wave propagates though the pipe wall through coupling. When the reflected guided wave in pipe passes through the coupled MsS probe, the physical deformation of ferromagnetic strip causes the magnetic induction change that is picked up by the MsS adapter and ribbon cable. The MsS System saves the electric signal due to the magnetic induction during the receiving of ultrasonic wave.
In the common setup for pipeline inspection, MsS probes consist of ferromagnetic strips (0.15 mm thick) and ribbon cables (less than 4 mm thick) as shown in the figure. The thin probes can be applied to a pipe having a 25-mm or higher clearance between pipes. The MsS probe can generate longitudinal, torsional, and flexural modes by adjusting strip conditioning, strip size, and bias magnetization direction relative to AC magnetic field direction.
There are two types of MsS probes for pipeline inspection: Encircling probe and sector probe. The encircling MsS probes continuously covers the whole circumference (360°) of the pipe and strongly generate a torsional wave mode with a short dead zone. Thus, encircling MsS probe allow for an inspection of up to 500 feet in each direction in aboveground painted pipes in good condition with a defect detection sensitivity of approximately 2-3% of the total pipe wall cross section.
MsS Sector Probe
An MsS sector probe can be 4– to 12-inch-long and is used to cover only a section of pipe circumference. It is used for medium range (5 to 20 ft) high-resolution inspection. It is effectively used for inspecting pipe supports or pipe shoe areas, wall penetration pipe, soil-air interface, concrete-air interface of pipe, and accurate inspection of large diameter pipes. Because the sector probe covers only a section of the pipe, its sensitivity is very high, not dependent on the pipe size.