Testing the thickness of metal structures
Simple traditional measurement with vernier or micrometer is not possible for sections without end access. In such cases, a specialist machine can be used to test for the thickness of a material.
The machines use Ultra-sonic sound waves, sent out from a transducer and received back by the same transducer and with software, translates the information that the machine receives into a direct readout of the material thickness.
Our machine is the latest type from Cygnus Instruments and although expensive, is a fantastic machine. It can automatically make allowances for surface coatings on one or both sides of the material being tested, and it can be pre-set to work with different materials, which have different sound transmission characteristics.
The operator in this picture is working within a ship's hull and taking readings through the hull plates. A simple couplant is used to exclude air from between the transducer and the surface being tested. The couplant is water soluable and does not affect most surface coatings.
The readings obtained can be selected in mm or inches.
Calibration of the machine can be carried out using test pieces or specific materials, or on site using accessible edges of the same material which can be tested by the machine, and the results compared with the neasurements taken physically with a vernier caliper or a micrometer.