Aplicaciones

Application Notes

Ultrasonic Thickness Measurements of Hot Metals

Ultrasonic thickness gauging is not just limited to materials at normal (ambient) temperatures. The thickness of a part can be measured even when the surface temperature approaches 900 deg F (500 deg C). In metals, particularly, there may be circumstances when the thickness of the part needs to be measured before the part can be cooled down.

Ultrasonic testing has the advantage - just as at normal temperatures - that thickness measurements can be taken from one side of the hot part. Ultrasonics may be the preferred method of measurement even when both sides of the hot metal part are accessible. The reason is that ultrasonic thickness measurements can be made instantly and with very brief contact with the hot surface.

For the best calibrated accuracy, the effect of the higher temperature on the velocity of sound must be taken into account. Although change in sound velocity with temperature is much less in metals than in plastics, significant errors in measured thickness can result if sound velocity is not corrected.

Equipment: A major reason to classify hot metals separately is that when the temperature of a surface exceeds 120 deg F (50 deg C), Microscan contact transducers cannot be used because they will be damaged by thermal expansion effects. Consequently, gauges that exclusively utilize contact transducers cannot be used for making thickness measurements on hot surfaces.

We recommends the Model 35DL, which can be used with delay line transducers or immersion transducers. On hot surfaces delay line transducers must be used with selected High Temperature delay lines.
The thickness of hot corroded metal parts or parts with rough surfaces should be measured with the Model 38DL PLUS and a D790 or D791 dual transducer. The 38DL PLUS is a sophisticated multipurpose gage with internal data loggers and waveform displays that have practical features to provide excellent thickness measurement reliability on hot corroded metal pipes or tanks. For less challenging applications, the compact MG2 series of gages can also be used.

Products used for this application

35DL

El modelo 35DL de bolsillo es un medidor de espesor por ultrasonidos portátil para realizar mediciones precisas sobre metal, plástico, caucho, vidrio y materiales compuestos, utilizando palpadores de un elemento. Tiene las mismas características que el modelo 35, pero incluye un registrador de datos interno.

38DL PLUS

El 38DL PLUS es un medidor de espesor por ultrasonidos de avanzada. Utiliza un palpador dual para la inspección de superficies internas corroídas e incluye las funciones THRU-COAT y eco a eco. También utiliza palpadores de un elemento para medir con precisión los espesores de materiales finos, muy espesos o de múltiples capas.

MG2

El medidor de espesor por ultrasonidos portátil MG2 utiliza los palpadores duales en aplicaciones en las que se debe controlar la corrosión. Cuenta con numerosas funciones de base, como el modo Mín/Máx, que mide y recuerda las medidas de espesor mínimo a una velocidad de 20 lecturas por segundo, el modo Congelamiento para capturar en forma instantánea el espesor crítico y el modo Compensación cero.