Measurements of Silicone Coatings on Porcelain High Voltage Insulators
Application Notes
Thickness = Velocity x One-Way Transit Time
The accuracy of measurement will be proportional to the accuracy with which the time interval is measured and the accuracy to which the sound velocity is known. For silicone coating measurements, accuracies of ± 5% can usually be achieved.
Equipment: The recommended instrument for silicone coating measurement is a specially set up Evident Model 38DL PLUS or 45MG with Single Element software portable thickness gage with an M2055 handle-style 20 MHz delay line transducer. Measurements can be made over a thickness range of approximately 0.005 in. (0.12 mm) to greater than 0.050 in. (1.25 mm). Gage setups for measurement of silicone over porcelain are dedicated to this application and should not be used for other types of testing.
Procedure: Using a properly set up gage, couple the transducer to the measurement point using firm and steady pressure. Normally, it will be necessary to use a drop of liquid couplant (glycerin, propylene glycol, oil, or water) between the transducer tip and the test surface to insure good coupling of sound energy. The gage will display the thickness of the silicone coating at the point of measurement. Gage calibration should be periodically verified using a reference standard consisting of a known thickness of silicone bonded to a ceramic base. For acoustic reasons it is essential that the reference standard exactly duplicate measurement conditions; unbonded silicone may not be used. We can supply further gage calibration information on request.
72DL PLUS
The 72DL PLUS™ advanced ultrasonic thickness gauge delivers precision thickness measurements at high speed in a portable, easy-to-use device. Compatible with single element transducers up to 125 MHz, this innovative instrument is ideally suited to measure the thickness of ultra-thin materials, including multilayer paint, coatings, and plastic. It can simultaneously display the thickness of up to 6 layers.
45MG
The handheld 45MG ultrasonic thickness gauge is packed with measurement features and software options. This unique instrument is compatible with the complete range of Evident dual element and single element transducers, making this gauge an all-in-one solution for virtually every thickness gauge application.
38DL PLUS
The 38DL PLUS is an advanced ultrasonic thickness gauge. Uses dual element transducer for internal corrosion applications, and has features that include THRU-COAT technology and echo-to-echo. Uses single element transducers for very precise thickness measurements of thin, very thick, or multilayer materials.
