Industrial sensors are very sensitive components that are used to monitor temperatures, flow rates and pressure over long periods of time; and in applications relating to oil and gas pipelines, they are subjected to extreme stresses while doing so.
Each day, about 160,000m3 pass through a 1m-diameter pipeline — the equivalent of 1,850 litres per sec. Furthermore, onshore gas pipelines are subjected to internal pressures up to 100 bar (the figure is 200 bar or more for offshore pipelines). Sensor elements used to monitor flow suffer considerable wear as a result of corrosion and abrasion, shortening their life and necessitating costly repairs.
Thanks to an innovative powder nozzle developed by OR Lasertechnologie GmbH (
www.or-laser.com), a method of ‘cladding’ known as DMD (direct metal deposition) can be used to greatly prolong the life expectancy of these
sensors.
The company’s compact EVO Mobile laser welding system can apply wear-resistant coatings, as well as carry out repairs or modifications; and while it uses relatively low laser output levels (starting at 200W), its high deposition rate of up to 5,000mm3/hr makes it suitable for a wide range of applications.
Conventional methods of applying Stellite cladding involve intense heat that shortens the life of sensors, whereas the laser only minimally melts the surface of the sensor, and then only at ‘scattered’ points.
Metallic powder with grain in the size range 45-90µm is fed coaxially to the laser beam and permanently fused to the sensor’s surface. The advantages of this approach include precise deposition of the material, low heat penetration, and an undistorted crack-free coating.
Track widths between 200µm and 2mm are possible. This coaxial arrangement also allows material to be deposited independently of the direction of cladding; with a workpiece free to be moved in all directions, it is possible to “grow” layers in three dimensions.