Sulzer creates hybrid AM process for Chevron

The trial workpiece clamped in position.[/caption]

Sulzer creates a hybrid additive manufacturing process to minimize lead time on components for Chevron

Chevron and Sulzer are moving forward with their joint partnership after forming two years ago with the goal of reducing parts inventory and improving flexibility. Sulzer developed and implemented additive manufacturing technology to produce new pump impellers without the need for tooling.

The project offers Chevron the potential to reduce lead times for new parts without compromising on quality. The collaboration also involves other partners such as suppliers of equipment for the manufacturing cell, powder suppliers, audit and certification bodies.

Companies involved in oil and gas production hold parts inventories to minimize downtime, especially when process-critical assets are involved. With so much capital invested in parts, any strategy that would allow this to be reduced without compromising reliability and productivity warrants in-depth examination.

The ability to create complex components, such as pump impellers within a few days has the potential to cut inventory costs significantly.

Pumping systems are central to moving raw materials as well as the finished product, and many processes in between. So, standby pumps are retained as well as spare parts, such as impellers.

The technology incorporates laser metal deposition and precision machining. Additive Manufacturing (AM) using this technology can create finished parts in one machine, significantly reducing lead times.

The laser metal deposition head[/caption]

Simplifying complex geometries

Starting with a piece of stock material of the required grade and quality loaded into the hybrid machine tool, it is possible to machine the most complex geometries of the eye of the impeller. Material is then added and finish-machined while remaining in the same cell. This process enables Sulzer to create finished machined quality on far more complex components than would normally be possible with a conventional machine tool.

In addition to all the standard cutting tools that are stored in the tool changer, there is also the laser metal deposition head, which can be used to build up material on the workpiece, or core. The machine can quickly change between the milling tools and the laser head, a process that would normally require the component to be repositioned in a separate machine.

The additive technology has also required the development of new processes, using a fine powder, 50 to 100µm, and a laser. The powder is melted by the laser and deposited on the surface of the stock material held in the hybrid machine tool.

Hybrid impeller manufacturing

Sulzer has been a pioneer in developing technology for pumps and other rotating machinery for more than 100 years. Now, the company is using this latest development to manufacture precision parts, such as impellers.

Pump impellers are complex components to manufacture, the internal geometry is too complicated to be created by a conventional milling machine. Starting with a forging, the core of the impeller can be machined using a 5-axis milling machine. Then further material is added to the outside of the impeller using laser metal deposition.

The use of milling tools means that the internal hydraulic surfaces have a very high-quality finish, much better than those achieved with a casting process. The process of adding material and machining is repeated until the complete impeller emerges. The whole process, which can be completed in a matter of days, is much quicker than casting a new component, which can typically take 15 – 20 weeks.

The reduced build time for a new impeller means that, in the event of a pump needing a new component, the standby pump can be brought online while the new part is manufactured and delivered. Although this time could be reduced further if necessary, the consensus is that a few days is enough for most applications.

Trials of the combined 5-axis CNC milling and laser metal deposition head[/caption]

Proving the theory

The development work has now been put into practice and applied to a real-world application. Chevron has a CPT pump from Sulzer operating with a corrosive fluid, an application that requires specific material properties to ensure the durability of the pump. The impeller was identified for replacement and an ideal subject for the new manufacturing process.

Using the original design drawings, a 3-dimensional model was fine-tuned and a final set of coded instructions for the hybrid manufacturing machine was generated. Within a few hours the new impeller had been created and was ready to be installed.

The new impeller was installed in the pump and tested at Sulzer first. It has now been operating successfully since its installation on site in 2019. Both Sulzer and Chevron are confident in the performance and durability of the new component.

Chevron has a strategic plan to take advantage of new and innovative technologies that can offer improvements for its operations and improve efficiency. One of these is additive manufacturing. This process is also important for components that are now obsolete, enabling parts for heritage assets to be sourced with a short lead time.