Portable Hardness Testing for Installed Plant and Fabrication

Hardness testing establishes a material's resistance to indentation, which correlates with tensile strength and shows whether heat treatment, welding or service conditions have altered the material as intended. itmad's NDT technicians perform portable hardness testing at the client's site, on installed plant and on fabrication in progress, as well as on components submitted to the laboratory, by Leeb, UCI, Brinell, Rockwell and Vickers methods to ASTM and ISO standards. itmad operates across the Middle East, Asia and Europe. Last reviewed: October 2026.

Test methods

The Leeb rebound method (ASTM A956) fires an impact body at the surface and measures the ratio of rebound to impact velocity, giving a Leeb value that is converted to Brinell, Rockwell or Vickers. It is fast and suits large or heavy components, but it needs sufficient mass and surface preparation to be valid and is unreliable on thin sections and small parts. Ultrasonic contact impedance (UCI) loads a Vickers diamond into the surface and measures the shift in resonant frequency of the vibrating rod, so it works on thin walls, small components, welds and heat-affected zones where Leeb cannot be applied, and it leaves a very small indentation. It is the preferred portable method for weld and HAZ surveys.

Portable Brinell presses a tungsten carbide ball into the surface under a known load and measures the indentation optically. Because it produces a physically measurable impression, it gives a direct result and not a converted one, and it is accepted where a specification will not permit converted values. The Telebrineller impact test drives a test bar and the component simultaneously against a ball and compares the two indentations, and the Poldi test applies the same comparative principle with a reference bar of known hardness. Both are comparative and not absolute, useful where access or position prevents a loaded instrument being applied, and long established in field verification of piping and pressure equipment. Rockwell and Vickers are direct indentation methods used where the component and specification allow, with Vickers applied where its small indentation permits testing of welds, heat-affected zones, coatings and case-hardened layers close to an edge.

Standards and conversion

Testing is performed to the standard that the specification calls up, including ASTM A956 for Leeb, ASTM E110 for portable Brinell and Rockwell, and ASTM E10, E18 and E92 for the corresponding bench methods. ISO 6506, 6507 and 6508 are applied where an ISO reference is specified. Where a result must be reported in a scale other than the one measured, conversion follows ASTM E140 or ISO 18265, and converted values are identified as such.

Where hardness testing is required

It verifies post-weld heat treatment, confirming that the weld and heat-affected zone are within the specified hardness range, and sour service compliance, where limits such as those in NACE MR0175 / ISO 15156 apply to welds and parent material. It is used to confirm material grade or condition where documentation is missing or in doubt, to detect in-service hardening from creep, carburisation or thermal exposure, and to verify case hardening, nitriding and surface treatment depth and result. It also supports incoming material inspection against mill certificate values and failure investigation, establishing whether hardness contributed to cracking or fracture.

Sector applications

In oil and gas, hardness limits on welds are a contractual and safety requirement in sour service, and hardness surveys are routine after any field weld or repair. In power generation and process plant, hardness is used to monitor high-temperature components for degradation, and in structural fabrication and automotive work it verifies heat treatment and material substitution. Testing is non-destructive in practice, so it can be applied to installed plant and finished components.

What the client receives

A report that identifies the method, instrument and standard applied, with test locations recorded by weld number, component or drawing reference. Individual readings are given and not an averaged figure alone, the scale measured and any conversion applied are stated explicitly, and the results are assessed against the acceptance limit in the specification. Instrument calibration traceability is provided on request.

Frequently asked questions

What does hardness testing tell you?

A material's resistance to indentation, which correlates with tensile strength and shows whether heat treatment, welding or service conditions have altered the material as intended. It is routinely applied to installed plant and to fabrication in progress.

Which portable method suits welds and heat-affected zones?

Ultrasonic contact impedance (UCI) is the preferred portable method, because it works on thin walls, small components, welds and HAZs where Leeb cannot be applied, and leaves a very small indentation. The Leeb method is unreliable on thin sections and small parts, which is why UCI is used instead.

When is portable Brinell used?

Where a direct result is needed and not a converted one, since it produces a physically measurable impression. It is accepted where a specification will not permit converted values.

Which standards apply?

ASTM A956 for Leeb, ASTM E110 for portable Brinell and Rockwell, ASTM E10, E18 and E92 for bench methods, and ISO 6506, 6507 and 6508 where specified. Conversions follow ASTM E140 or ISO 18265 and are identified as such.

Why is hardness tested for sour service?

Limits such as those in NACE MR0175 / ISO 15156 apply to welds and parent material in sour service, so hardness surveys are routine after any field weld or repair. They also verify post-weld heat treatment.

Does the report give individual readings?

Yes, individual readings and not an averaged figure alone, with the scale measured and any conversion stated explicitly. Results are assessed against the acceptance limit in the specification.