Steel Tank's End-cap Dimensions

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A manufacturer in Brazil designs and builds tanks and vessels for use in various chemical and petrochemical industries.  The tanks built from carbon or stainless steels, are fabricated in sections and welded together in a final assembly.  They are required to maintain strict dimensional tolerances for the pre and final assemblies.  The company approached Acuity to assist in improving their dimensional measurement practices.

Manufacturers must control the dimensions of the fabricated vessel

vesselCurrent quality control tool - a wooden template the same shape as the endcap

The round caps are later welded to the tank body

The manufacturer currently verifies the shape and dimensions using manual methods.  Operators use a tape measure to determine the diameter of the hemisphereical endcap.  The resolution of this measurement technique is 1mm and the accuracy varies on the operator technique.  They have no method for measuring the interior profile dimensions of the tank's endcap.  For quality verification, operators insert a large, wooden template into each vessel and attempt to assess its fit.  They will look for gaps between the edge of the template and the surface of the vessel.  The plywood template is subject to thermal and moisture-induced expansion and contraction.  The templates require two operators.

Acuity AR1000 mesures to shiny steel

The solution to the measurement challenge was to use a non-contact laser distance sensor to measure the interior surface of the end-cap from a central measurement axis.  The rangefinder would be rotated 180°, measuring the distance from one edge, through the base and to the other edge.  This would allow not only the diameter, but also the entire profile of the shape.  This information could be transmitted to a computer for display and archiving.

The AR1000 laser distance sensor has a measurement resolution of 1mm and was successful in measuring all expected surfaces, including bright-ground steel, light oxidation, paint, oiled surfaces, black paint, gray paint, etc.  The planned orientation of the sensor guaranteed a strong laser reflection off shiny surfaces.

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