TPT September 2011

W elding E quipment

Quality-control methods for manufacturing welded tube and pipe

HIGH frequency resistance welding (HFRW), also referred to as electric resistance welding (ERW), is a major process used in the production of welded tube and pipe. HFRW mills operate at very high speeds, generally ranging from 50 to 500ft per minute, depending on material diameter and thickness. Application sizes range from hypodermic needles to pipelines. A wide range of commonly used metals can be welded, including low-carbon and alloy steels, ferritic and austenitic stainless steel, and many aluminium, copper, titanium and nickel alloys. In this continuous process, high- frequency current is concentrated in the formed strip edges and generates rapid heating in a small volume of metal at the weld interface. Pressure rolls are then used to force the edges together to produce a welded tube or pipe. Although the quality of the weld can be very high, a few weld-related quality problems exist. Modern non-destructive techniques such as eddy current and ultrasonic inspection are commonly used to detect open seam conditions such as cracks. However, the major problem that remains undetected is a condition referred to as cold weld (also called paste or stack weld) that is the result of improper welding parameters. Today’s inspection and non- destructive evaluation (NDE) techniques are not able to detect the cold weld condition. This condition is difficult to detect because it appears visually and metallurgically to be a good weld. A cold weld is usually welding process-related, and is typically revealed during mechanical testing or in service as a fracture or splitting along the weld seam. The EWI tube and pipe mill team is applying new quality-control methodologies and monitoring techniques to HFRW mills, resulting in significant reduction and eliminating weld quality problems related to premature weld seam failures due to a cold weld condition. Understanding the weld process variables and their relationship to the final weld characteristics and properties is key to the methodology developed by EWI. Full- scale testing and portable instrumentation capabilities at EWI are extensively supporting the tube and pipe mill projects. In-plant experimental techniques have been developed and refined to generate production mill process windows for a range of critical welding variables such as temperature, squeeze force, displacement

and mill speed. Monitoring the welding parameters can be completed with traditional data acquisition sensors and systems. Monitoring the resultant weld seam shape, size and characteristics is performed using a non-contact optical technology. This technology uses commonly available laser sensors to make measurements of the

surface profile of the pre-welded and just- welded tube surface. These profile images are compiled from three-dimensional surface topography data. Edison Welding Institute – USA Email: mkimchi@ewi.org Website: www.ewi.org

COMPANIES WHO BELIEVED IN a PaRTneRShIP wITh US:

ROYAL DUTCH SHELL

KELLOGS BROWN AND ROOT, USA

NORSK HYDRO, NORWEGIA

HEEREMAC, THE NETHERLANDS

FMQ, SAUDI ARABIA

WELDING PROCESSES: GTAW GMAW FCAW

QUALITY INTERNATIONAL, UAE

FLUOR DANIEL SADA, USA

CCIC, QATAR

SUEDROHRBAU, SAUDI ARABIA

STORK MEC, BELGIUM

NACAP ASIA PACIFIC, THAILAND

EXXON MOBIL, USA

OILSERV, NIGERIA

GENERAL ELECTRIC, USA

TEKFEN INSAAT, TURKEY

MONTER STROJARSKE MONTAZE, CROATIA

GALFAR E&C, OMAN

• AUTOMATIC PIPE WELDING SYSTEMS AND RELATED EQUIPMENT • FROM 6MM AND UP • INTERNAL/EXTERNAL

ARAMCO SERVICES, SAUDI ARABIA

CANADOIL ASIA, THAILAND

VAM, MCE GROUP, AUSTRIA

OAO LUKOIL, RUSSIA

LARSEN & TOUBRO LTD, INDIA

NIS-NAFTAGAS, SERBIA

PETROJET, EGYPT

KEVIEPSZER KFT., HUNGARY

KVV ZRT., HUNGARY

PETROFAC, UAE

ENI-SNAM, SAUDI ARABIA

BIN QURAYA EST, SAUDI ARABIA

and many mORe...

T +31 321 38 66 77 | F +31 321 31 41 65 | info@magnatech-international.com

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