Robots take the strain for Valen welders

1/18/2012 11:40 AM EST

Valen Fittings manufactures specialist butt weld fittings for the oil and gas sector from a wide range of exotic materials - currently 37 materials are used, none of which are ferrous.  The fittings are generally used in critical applications, usually offshore or in the ‘hot spots’ of oil and gas refining processes.

A wide range of sizes are covered, typically from 8 inch to 48 inch diameter.  Some fittings require a welder to weld continuously for up to 15 minutes.  Len Sandford, Managing Director of Valen, explains, “Valen is renowned for its quality of product and in particular its speed of order turn round which is exceptional for the sector.

“We continuously aim to improve productivity but because of the many fittings, types of material, range of thicknesses and low volume call off, we don’t have the luxury of being able to implement basic welding robot principles.  Our aim is always to adapt our existing manning skills so we can maintain the quality and reduce operator strain.”

Working with welding automation specialist Pentangle Engineering, Valen firstly addressed the issue of accurately plasma cutting part finished pressings.

A Fanuc Robotics M-16 iB, inverted on a jib is used to plasma cut edges and then to cut a weld preparation angle along the same edge.

“We realised that the system would require considerable development to accommodate the variances that would be presented to the robot.  No two pressings are ever the same because of the thickness and shapes we are producing,” continued Len, “Pentangle quickly grasped the requirement and produced a real time measurement solution using lasers and feedback voltage from the plasma cutter to provide realtime adaptive control.”

Pentangle developed  the system to allow the robot to find the start point initially then offset its frame  to compensate.  During initial cutting, the plasma voltage is constantly measured and used to control the torch height and path. This ensures precision cuts typically to within 0.5mm tolerance.  A laser sensor was built in to the plasma head by Pentangle to control the cut of the secondary, but equally critical, weld  preparation angle and maintain a constant 3 mm ‘land’ along the root face.

The robot has allowed the operator to be removed from the immediate work area of the inherently dirty operation and production time has typically been reduced on a thick 24 inch pressing from  around 1½ hours to 10 minutes.

Robot two is used to weld prepared sections, utilising a 6 axes FANUC Robotics ARC Mate 120-iC positioned with a single axis manipulator.  The cell uses a high resolution camera to observe the weld, and a joystick controlled slide system,  which is mounted on the 6th axis of the robot, to allow weld torch adjustments during the welding process.

Each complete weld can take up to 12 runs to complete.  During each run, the operator is able to view sidewall fusion and weld bead alignment on a monitor. By using the joy stick to jog in 0.5mm increments, he is able to make fine adjustments to the weld torch during welding.

Concluding, Len explains, “The quality of the weld still reflects the individual skill of the operator, but the overall appearance of the robot-finished weld seams has improved markedly.

“Our overall productivity has improved since the installation of the robots. They provide more consistency and the quality they deliver is faultless.  From a project point of view we knew what we wanted to achieve - we didn’t want a large team looking after  each cell -  we wanted a simple one man operation that allowed our existing skilled  operators to have a simpler, safer, cleaner, and less stressful way to work – and we believe we’ve achieved that.”