Customer's Challenge

Each in-situ machining project presents unique challenges based on site conditions, such as limited access, concurrent activities, lack of lifting equipment, and structural fabrication tolerances. These challenges require unconventional thinking and adaptability from experienced in-situ machining specialists. During the COVID-19 pandemic, one of our repeat assignments involved machining the foundation pads of a fire pump onboard a Floating Production Storage and Offloading (FPSO) unit. Due to limited rigging and lifting support at the yard, a new approach was needed.

The GD&T (Geometric Dimensioning and Tolerancing) required a flatness runout of less than 0.2mm for each foundation pad and no more than 1mm variation across all ten pads. These pads were welded to support beams spanning 11 meters, with five pads spaced 1.2 meters apart on each beam. Two parallel support beams, spaced 2 meters apart, were located on the vessel’s deck.

In previous jobs, a standard portable linear milling machine was set up three times to complete the machining process, with the help of laser alignment tools. This time, due to limited site resources, an alternative method was required.

Solution

Faced with site constraints, our field service team developed an innovative solution. After discussions with the client, we decided to deploy two linear milling machines and incorporate additional foundation frames. These frames were placed and tack welded between the landing pads, as shown in Photo 1.

To further optimize the process, we extended the cross beams of the milling machines to accommodate two milling spindles at each end, as illustrated in Photo 2. This setup minimized the need for heavy lifting and rigging during the machining process, streamlining the operation and reducing site downtime.

Benefits

Though the design modifications and setup required extra preparation compared to previous assignments, this new approach significantly minimized lifting and rigging requirements, eliminating long wait times. Despite a slower start, the team completed the project within the committed timeframe, achieving the necessary tolerances.

By adapting to site limitations with creative problem-solving and efficient use of resources, we successfully delivered the project while maintaining high quality and meeting strict deadlines.