TPT January 2014

Technology News

Steam generator tubing MANY of the world’s nuclear power generation reactors use pressurised water reactor (PWR) designs. The nuclear reaction generates tremendous heat and by way of a heat exchange system produces steam, which drives turbine electricity generators. in stress corrosion cracking of the tube walls in service. All such tubes go through a straightening process before being formed into U tubes and therefore they must be straightened, ensuring that they are subjected to minimum excess strain during this cold working process. Turner has developed straightening machinery control systems to enable precision straightening without creating unacceptable stresses in Alloy 690 tubing.

of non-marking driven hyperbolic rolls). This unit grips the tube and starts it revolving slowly while feeding the end of the tube into the first pair of rolls in the straightening machine. The machine is equipped with a feature that allows the roll to move below the pass-line of the machine. This creates a gap between the first pair of machine rolls allowing the tube to move into the machine without contact with the rolls. When the tube leading end arrives between the first pair of rolls, the bottom roll lifts up into position. With the tube now in the first pair of rolls a specially controlled drive motor control system enters a highly developed control sequence, which carefully feeds and accelerates the machine up to its full production speed. The rpm of the tube is therefore accelerated following a Turner proprietary speed algorithm. Turner – USA Email: rpage@turnermachineco.com Website: wwwturnermachineco.com

The heat exchangers consist of primary coolant loops comprised of thousands of steam generator tubes directly circulating water from the reactor under high pressure and high temperature. These tubes are commonly referred to as “U tubes”. These heat exchange tubes are usually about 18mm in diameter and the most commonly used tube material is Alloy 690. Steam heater tube deterioration is a major problem in the operation of PWR installations and all processes in the production of U tubes must be very carefully controlled. Specifically, cold working of Alloy 690 must be carried out in a very controlled manner to ensure that the tubes are free from defects, which would result

U Tubes are usually very long (up to 40m). To straighten these long tubes it is necessary to do the straightening at a reasonable speed to keep up with high volume production needs. During straightening, the tube will revolve at high speed. If the machine rolls were to grip the end of the tube and immediately start to revolve the tube, unacceptable torsional stresses would be induced along the tube. With the Turner-developed combination of systems, the stationary tube is carefully gripped by a “cross roll feeder unit” (pair

since 1910

SHAPE FUTURE WITH PIONEERS !

© FotoLyriX - fotolia.com

TAKING CUTTING INTO THE NEXT PHASE

TCT-CIRCULAR SAW BLADES FOR CUTTING BAR/TUBE/PIPE

TENRYU SAW MFG. CO., LTD. | Japan, Fukuroi, www.tenryu-saw.com TENRYU EUROPE GMBH | Germany, Aalen, www.tenryu.de TENRYU AMERICA INC. | USA, Hebron KY, www.tenryu.com

TENRYU SAW DE MEXICO, S.A. DE C.V. | México, Silao, Guanajuato, www.tenryu.mx TENRYU (CHINA) SAW MFG. CO., LTD. | P.R. of China, Langfang, Hebei, www.tenryu.cn TENRYU SAW (THAILAND) CO., LTD. | Thail., Amiphur P., Rayong, www.tenryu-saw.com TENRYU SAW INDIA PVT. LTD. | India, Neemrama, Rajasthan, www.tenryu-saw.com

.

64

www.read-tpt.com

J anuary 2014