Portable Hardness Testing Services

Hardness testing establishes a material's resistance to indentation, which correlates with tensile strength and indicates whether heat treatment, welding or service conditions have altered the material as intended. ITMAD's NDT technicians perform portable hardness testing at your site, on installed plant and on fabrication in progress, as well as on components submitted to the laboratory.

Test methods

• Leeb rebound — ASTM A956An impact body is fired at the surface and the ratio of rebound to impact velocity is measured, giving a Leeb value converted to Brinell, Rockwell or Vickers. Fast and suited to large or heavy components, but it requires sufficient mass and surface preparation to be valid, and is unreliable on thin sections and small parts. Equotip and Time/Mitech instruments.
• Ultrasonic contact impedance (UCI)A Vickers diamond is loaded into the surface and the shift in resonant frequency of the vibrating rod is measured. UCI works on thin walls, small components, welds and heat-affected zones where Leeb cannot be applied, and leaves a very small indentation. The preferred portable method for weld and HAZ surveys. Krautkramer instruments.
• Portable BrinellA tungsten carbide ball is pressed into the surface under a known load and the indentation measured optically. Because it produces a physically measurable impression it gives a direct result rather than a converted one, and is accepted where a specification will not permit converted values. Mohr & Federhaff and King testers.
• Telebrineller impact testA hammer blow drives a test bar and the component simultaneously against a ball, and the two indentations are compared. Comparative rather than absolute, useful where access or position prevents a loaded instrument being applied, and long established in field verification of piping and pressure equipment.
• Poldi hardness testThe same comparative principle using a reference bar of known hardness. Simple and robust, applied where a quick field indication is required rather than a certified value.
• Rockwell and VickersDirect indentation methods carried out with Akashi instruments where the component and specification allow. Vickers is applied where the 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 your 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. Converted values are identified as such in the report, since conversion between scales carries inherent uncertainty and some specifications will not accept it.

Where hardness testing is required

• Verification of post-weld heat treatment, confirming the weld and heat-affected zone are within the specified hardness range
• Sour service compliance, where limits such as those in NACE MR0175 / ISO 15156 apply to welds and parent material
• Confirming material grade or condition where documentation is missing or in doubt
• Detection of in-service hardening from creep, carburisation or thermal exposure
• Verification of case hardening, nitriding and surface treatment depth and result
• Incoming material inspection against mill certificate values
• 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. 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 components already in service.

Accreditation and approvals

ITMAD is accredited to ISO/IEC 17020 as an inspection body, is an ADNOC approved inspection contractor, and is listed on the Abu Dhabi City Municipality register of Approved Third Party Inspection Bodies. Certificates are issued in the format required by the governing authority, including Dubai Municipality and the Dubai free zone authorities, and inspection is carried out across Dubai, Abu Dhabi, Sharjah and the northern Emirates. Testing is carried out by technicians qualified to ISO 9712 and ASNT SNT-TC-1A Level II.

What you receive

• A report identifying the method, instrument and standard applied
• Test locations recorded by weld number, component or drawing reference
• Individual readings rather than an averaged figure alone
• The scale measured, and any conversion applied, stated explicitly
• Assessment against the acceptance limit in your specification
• Instrument calibration traceability on request