The presence of hydrogen in industrial plants is a source of damage. HTHA is one such form of degradation which is due to the formation of methane (CH4) by reaction with carbides in steel. HTHA can occur either in the parent material or in the weld itself and manifests itself in several types of alloys. The probability of HTHA damage in any given plant is dependent on the partial hydrogen pressure and operating temperature. Methane formed by the reaction accumulates at internal voids on the grain boundaries, where at certain conditions the build-up can produce micro-cracks. In the weld material this leads mostly to a leak-before-break situation, but when the damage is in the parent material the result is often catastrophic for people and the enviroment.

Since even a minor failure could cause unacceptable downtime and a substantial loss of money, conducting regular HTHA inspections is vital to detecting failures and discontinuities at the earliest stage possible.

Detection of HTHA with NDT is extremely difficult, and can only be done reliably by a few companies in the world (including SGS) that have deep knowledge and experience with this type of degradation.

In order to assess the condition of their piping and heat exchanger, the refinery in Batangas, Pilipinas Shell Petroleum Corporation, looked for a reliable inspection, verification and testing company with many years of experience in the detection and quantification of the possible presence of HTHA.

On October 21, 2011, SGS was awarded a contract, scheduled from October 24-28, 2011, to provide comprehensive HTHA inspection, due to more than 20 years of experience and competence in projects of this kind.  

During the HTHA inspection, SGS’s team of highly skilled experts, qualified and certified to conform with both European (EN473) and American (ASME) standards, inspected the piping and heat exchanger for the possible presence of HTHA by using the inspection procedures developed by SGS. These procedures are based on years of experience and the recommendations of the API 941. By using highly skilled experts and SGS’s inspection procedures, it is ensured that an advanced HTHA inspection is reliably performed.

The NDT team of SGS used a combination of various inspection methods to ensure the highest probability of detection of HTHA. In order to inspect the parent material of the piping and heat exchanger, SGS’s experts utilized the advanced backscatter technique and the velocity ratio technique. SGS’s regional expert teams are gaining a lot of experience supported in the field by expert teams coming from Europe.

Furthermore, SGS inspected the welds for micro- and macro cracks by means of ultrasonic testing (UT). In case of any indication of HTHA cracking, SGS carried out time of flight diffraction (TOFD) and manual pulse echo on welds for verification.

With SGS’s assistance, a reliable HTHA inspection was performed within the scheduled time, to the full satisfaction of the client.

For further information, please contact:

Julian M. Bernardo
Business Manager
SGS Philippines, Inc.
2nd Floor Alegria Building,
2229 Chino Roces Ave.,
Makati City, PO Box 2174,
t: +63 2817-5656
f: +63 2818-2971

About SGS

As the world’s leading inspection, verification, testing and certification company, SGS has accreditations to all major standards and is recognized as a leading global benchmark in the field of inspection, verification, certification and testing. With an experienced and qualified staff, SGS operates an extensive network of offices and laboratories in various fields, which offer a wide range of product certification services.