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Sensor life extended by new manufacturing technique

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World Pipelines,

Direct metal deposition (DMD), an additive manufacturing technique, has been developed by an O.R. Lasertechnologie company to enable reliable protection of sensor elements by means of a hard alloy. It makes it possible to significantly extend their lifetimes in the pipelines of the oil and gas industry.

Industrial sensors are very sensitive components that are deployed to precisely and reliably monitor temperatures, flow rates and pressure over long periods of time.

Their use in oil and gas pipelines serves as a good example since they are subjected to extreme stresses. Each day, about 1 million bbls of crude oil, or 160 000 m3, pass through pipelines with a diameter of 1 m – equivalent to 1850 l/sec. Onshore gas pipelines have an extremely high internal pressure of 100 bars, which can reach up to approximately 200 bars or more in offshore pipelines. Sensor elements used to monitor the flow suffer considerable wear as a result of corrosion and abrasion. This shortens their lifetimes and necessitates costly repairs.

Thanks to the development of a powder nozzle by OR Laser, the technology of powder-based laser cladding (DMD) can be used to prolong the life expectancy of these sensors.

The EVO Mobile laser welding system is well suited for applying wear-resistant coatings and carrying out repairs or modifications. The system uses relatively low laser output levels, starting at 200 watts, but its high deposition rate of up to 5000 mm³/hr makes it ideal for a vast range of applications.

To lastingly protect a sensor from wear, a Stellite coating could be used. The cobalt-chromium-based alloys known by this name are very difficult to machine. The conventional approach is to apply composite clad layers with a total thickness of several millimeters. However, the intense heat applied during the process results in considerable mingling of the sensor’s material with the Stellite cladding. Therefore, use of the conventional method considerably shortens its lifetime.

Unlike conventional methods, the laser only minimally melts the surface of the sensor, and only at scattered points. Metallic powder, with grain sizes between 45 and 90 µm, is fed coaxially to the laser beam and permanently fuses with the object’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 200 µm and 2 mm are possible.

The coaxial arrangement also permits deposition of material independently of the direction of cladding, so that the workpiece can be freely rotated in all directions and even ‘grow’ in three dimensions. Moreover, the laser parameters can be dynamically adjusted to changing conditions on the fly.

In order to prevent oxidation and the formation of bubbles, the work is done in a shielding atmosphere of argon. The resulting surface quality is like new, free of pores and cracks, very close to the required final contours, and neat.

“We’re proud of having found a way to increase the durability of these sensors with our additive laser technique and thus improve the reliability of gas and oil pipelines,” commented Markus Wolf, Head of the R&D department at OR Laser.

Adapted from press release by Anna Nicklin

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