Dakota Digital CMX operation manual Chapter Nine Pulse-Echo Coating & Coating Techniques

CHAPTER NINE

PULSE-ECHO COATING & COATING TECHNIQUES

9.1 Introduction to Pulse-Echo Coating Measurement (PECT)

In the previous sections we’ve discussed the need for detecting pits and flaws (pulse- echo) in materials, along with the requirement to measure through and eliminate errors caused by coated materials (echo-echo). Until now, both modes were needed in order accomplish both tasks. Pulse-echo mode was used for flaw detection, and echo-echo mode was used to eliminate the coating thickness and provide a nominal material thickness only. With this in mind, it often became cumbersome toggling between both modes respectively.

In a majority of applications involving coated materials, inspectors are often interested in monitoring both the thickness of the material, as well as the thickness of the coating . Therefore, the CMX has been designed to provide the user with the ability to measure the material and coating thicknesses simultaneously, while maintaining the ability to detect flaws and pits all in a single mode called Pulse-Echo Coating (PECT). This is accomplished by using a custom hybrid combination mode utilizing properties from the basic modes along with a group of special techniques and theoretical wave phenomena’s.

The CMX is preset to a coating velocity of 0.0850 in/µsec (2159 m/sec) from the factory. This velocity is a very close approximation of the common coating velocities found in the field. However, the CMX also has a built-in one and two point calibration options to calibrate to coating samples with a known thicknesses.

There are two coating modes built into the CMX:

1)Pulse-Echo Coating (PECT) – used during inspections where both the material and coating thicknesses are required.

2)Coating Only (CT) – used during inspections where only the coating thickness is required.

9.2Enabling Pulse-Echo Coating Mode (PECT) & Coating (CT)

When the CMX is initially powered up, the gauge will automatically check to see if the transducer plugged into the gauge can be recognized. All Dakota Ultrasonics coating enabled transducers are equipped with the auto recognition feature. If the CMX doesn’t recognize tha t a special coating enabled transducer is plugged into the gauge, the coating feature will be disabled entirely. There are a number of coating enabled transducers available from Dakota. Please contact us with your application requirements for additional information on frequencies and diameters currently offered.

The coating modes can be enabled in three different ways:

1)On Power up and probe recognition.

2)By pressing MULTI MODE keypad.

66