Portable Hardness Testing on the Asset in Service

It is a non-destructive test that determines a material's resistance to localised indentation. An indenter is applied under a known load and the load is related to the size of the impression, or the rebound velocity of an impact body on the surface is measured. The result is expressed on the Brinell, Rockwell, Vickers or Leeb scale and compared with the range set by the component's specification.

The choice depends on the material, the thickness of the part, the surface finish and the access available. Vickers resolves spot measurements in narrow areas such as the heat-affected zone of a weld; Brinell works better on coarse-grained materials because it averages over a larger indentation; Rockwell reads directly on treated steels; and Leeb allows measurement with portable equipment on heavy parts installed in the plant.

No. The measurement is taken with a portable tester on the asset, in the field and in its service position. Only the surface at each point is prepared, to remove paint, oxide or a decarburised layer that would distort the reading. No coupons are extracted and the component is not cut, so the equipment returns to service without repair.

To verify that the base metal, the weld and the heat-affected zone remained within the accepted hardness after post-weld heat treatment. A value above the limit points to an incomplete treatment, cooling that was too fast, or a consumable other than the qualified one: conditions that reduce the toughness of the joint and encourage cracking in service.

The identification of the component and of every point measured, the scale and load used, the instrument employed together with its verification against reference blocks, the values obtained, the comparison with the limit in the applicable specification, and the signature of the qualified technician who performed the test.