In April 2009, Shanghai ShenTong Metro Co. Ltd contracted SGS China and the Xuzhou Railway Engineering Department to provide third-party technical inspection of the track welds of eight Metro Lines under construction.

Once completed, the total length of the 16 Metro Lines will cover 400 km., making up over 35% of the city’s mass transit system. The municipal government is aiming to finish the project in time for the World Expo 2010.

The construction and maintenance of Metro Lines is a project with a high degree of responsibility. Aside from developing Shanghai into a modern metropolis, of topmost concern is safety; the tiniest flaws in the tracks as well as the smallest failures in the welds of the tracks can cause accidents when the train is in operation.

A team of six experienced, highly skilled SGS inspection engineers will ensure that failed welds are identified, analyzed and eliminated. Moreover, the SGS engineers will confirm that the track welding is in accordance with the applicable codes and norms of the Chinese Railway Ministry.

In order to identify failed track welds, SGS experts apply the Ultrasonic Testing (UT) method. The UT process involves the transmission of short wavelength sound waves at high frequencies. The sound energy spreads through the material in the form of waves. If there is a discontinuity or crack on the wave path, the “sound” will reflect back and be transformed into an electrical signal, which in turn will be displayed on the screen of the ultrasonic equipment.

The UT method is one of many Non-Destructive Testing Methods offered by SGS. Our services vary from standard Non-Destructive Testing Services to Advanced NDT Techniques like Risk Based Inspections, Time of Flight Diffraction, Corroscan, Digital Radiography and Guided Wave Inspection, also known as Long Range Ultrasonic Testing.

SGS Industrial Services is one of the biggest business industries under the SGS Group, the global service provider for Technical Verification, Inspection, Testing and Conformity Assessment. SGS ensures that the customer’s installations, material, equipment, facilities and projects meet all quality and performance requirements, whether they are regulatory, voluntary or customer-based.


Leaf Huang
Industrial Services Materials Lab
SGS-CSTC Shanghai Tongji Engineering Testing Co., Ltd.

SGS-CSTC Standards Technical Services Co., Ltd.
1/F, 17th Building Block1365, Kangqiao East Road,
Pudong District, Shanghai, China
t: +86 (021) 6818 3233*506
f: +86 (021) 6818 3122

About SGS

The SGS Group is the global leader and innovator in inspection, verification, testing and certification services. Founded in 1878, SGS is recognized as the global benchmark in quality and integrity. With more than 55,000 employees, SGS operates a network of over 1,000 offices and laboratories around the world.