Weld-edge preparation and collision detection

International Survey competing in the same segment. A specific consequence is that An a n n o u n c e m e n t from IC! the V3 PES plant at Fayetteville, Advanced Materials indicates that North Carolina, USA will now close it will withdraw from the with immediate effect. The V1 PES manufacture and sale of Victrex PES plant at Hillhouse, UK will close after (polyethersulphone) for the high the withdrawal period. One alternative to PES will be performance polymer market. The Chemical's Radel withdrawal will be completed over A m o c o the next 12 months. polyaryisulphone. Both materials During the withdrawal period, have their origins in Union Carbide's customers will continue to be discovery of the first means of supplied with ICI PES products to producing high molecular weight allow sufficient time for alternative aromatic polyethers; this patent also products and sources to be covers polyarylethersulphone and polyaryletherketone compositions. approved. Victrex PES is mainly used in the Amoco Chemicals purchased the Union Carbide's electrical, electronic and process assets of industries. During the 1980s, the engineering polymers business, key factor in establishing a including the polyarylether patents, successful PES business was seen in ]986. Further information: ICI by lCI to be the achievement of a Advanced Materials, PO Box 6, significant volume base. However, Shire Park, Bessemer Road, Welwyn the achieved growth has been Garden City AL7 ] HE). Tel: (0707) substantially less than anticipated, 323400; Amoco Chemicals, 15 rue due to the emergence of a large Rothschild, CH-1211 Geneva 21, n u m b e r of p o l y m e r variants Switzerland. Tel: +41 227 31 0281

No more Victrex PES

Glass.reinforced silicone tubing per. forms well in a high temperature radioactive environment

Silicone rubber tube protects actuators Glass-reinforced silicone rubber tubing proved to be about the only option for the pressure lines containing pneumatic actuators in two Magnox nuclear power stations. The actuators are used in devices which m e a s u r e the surface t e m p e r a t u r e of the pressure containment vessel outer wall. Around the reactor core is a vessel of stainless steel - the pressure containment vessel which contains the heat absorbing medium - inert gas, in this case. The temperature at the outer wall can reach 300°C and is carefully monitored by temperature probes attaching to the wall itself. These temperature probes are positioned using pneumatic actuators. PTFF tubing seemed attractive, but such materials decompose badly when exposed to nuclear radiation. Silicone rubber compared well in comparison to other synthetic rubbers. The reinforcement was necessary to cope with the air pressure used 100psi. Glass was chosen in preference to polyester as it can withstand higher temperatures (a standard polyester braiding will deteriorate at about 175°C) and it is inert and resistant to decomposition when exposed to nuclear radiation. Further information: SAMCO, Burleigh Business Centre, 52 Burleigh Street, Cambridge CB1 IDJ, UK. Tel: +44 (0223) 60750

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Weld.edge preparation and collision detection Using a plasma bevel unit from E S A B A u t o m a t i o n , profiling of metals where weld edge preparation is required can be carried out automatically, even where a combination of square edge and different bevel angles (+ and - ) on individual profiles are required. To prepare the weld edge effectively, it is only necessary to program the bevel angles, kerf width and material thickness. The exact setting of the bevel angle, the lateral movement and kerf compensation (hypotenuse compensation) are carried out within the NC control of the cutting machine. Torch to workpiece height is carried out whilst bevel cutting by a fixed cycle sensor, and by arc length control when cutting a square edge. A newly developed device which is integrated into the plasma torch holder will switch off the machine and the plasma power automatically to protect the torch from collision with any obstruction whilst cutting above, in or underwater. Cutting underwater is often recommended to reduce noise; with an integrated fume extraction hood, this will meet the most stringent COSHH require-

ments. Further information: ESAB Automation, 1-3 Crown Way, Walworth Industrial Estate, Andover, Hampshire SPI0 5LLI, UK. Tel: +44 (0264) 332074

Plasma bevel unit designed for weld edge preparation

MATERIALS & DESIGN Vol. 12 No. 5 OCTOBER 1991