K-Joint Weldconsultancy Project in New York USA.

Culture Shed Inc., located in Manhattan, New York, USA, has asked K-JW to be their welding and third party advisor for MRS 221 crane rail thermite welding. This crane rail is an integral part of the unique architecture of the Culture Shed building. The building has a movable roof, which can be positioned over the building or unrolled over the rails to connect an open square with the hall. The total is a large indoor area in which cultural events can be held such as dancing, music, markets, exhibitions etc. .

MRS 221 crane rail is the largest available crane rail and the separate elements can only be connected to one another to form a continuous length by the thermite welding process.

Thermite welding uses the very fast chemical (thermite) reaction of igniting a mixture of iron oxide and aluminum powder. Extreme heat is released, with temperatures in excess of 2,500 Celsius. An external heat source is not necessary during the process, and it is characterized by the fact that it cannot be halted once it is begun, as it continues till all available material is converted.

       

To carry out the process a ceramic mold is mounted over both rail ends, with a ± 30 mm gap between. Within this mold the thermite residue, consisting mainly of liquid iron, joins both molten rail ends together. To ensure a complete, fused connection both rail ends have to be preheated with gas burners until they are red hot.

The rail is made of the high strength material St.110 CrV. Thermite welding and the associated high temperatures creates a coarse crystal structure with moderate mechanical properties in the weld and the heat effected zones, near the weld on both sides. Low toughness is a result, with the material tending to break easily under high load if the weld contains imperfections such as poor fusion, slag inclusions, shrink cavities or porosity

Once the building is ready, a cracked weld can no longer be repaired and will result in the inability to move the roof: an unacceptable outcome. Therefore, the quality requirements for the Culture Shed rail are extremely high, with minimal weld imperfections permitted. In order to detect the smallest imperfections, Phased Array Ultrasonic Testing was used, a very sophisticated testing method which was of great importance in gaining maximum weld quality.

To make a reliable weld without imperfections one needs a proper welding procedure (WPQR), also necessary to form the basis for welder qualifications and welding implementation on site. Certification according to wellknown welding standards such as the EN-ISO 15614-1 and EN-ISO 9606-1 was the starting point. The BS-EN 14696-1-2006 + A1-2010 for thermite welding of railway applications only has a limited use. For this exceptional rail no appropriate standard was available, but with the structures of the above standards as a guide, it was possible to write a useful directive (Specification) that was comprehensive for quality assurance (QA) and quality control (QC).

The "Specification" was used to qualify the welding procedure and welders (welding operators); the requirements for nondestructive testing (Visual Testing, Magnetic Testing, Phased Array Ultrasonic Testing); the requirements for destructive testing (Hardness, Micro, Macro); for welding on site in New York with requirements for the welding procedure specification (WPS); the inspection and test plan (ITP); welding inspection; acceptance criteria; and welding registration and responsibilities

-Joint Weldconsultancy is also the preferred advisor for the designer of the Culture Shed mobile roof wheel construction, Hardesty & Hanover Engineering 1500 Broadway, New York, United States, 310.