Safeway walk-to-work gangway
The Challenge
Safeway designs and builds motion compensated gangways for safe transfer of personnel offshore from moving vessels to fixed Platforms and Wind Turbines Towers.
Each Safeway gangway is thoroughly tested on a Wave Simulation Platform (WSP). The WSP simulates vessel motions to guarantee that a walk-to-work gangway meets the harsh offshore environment demands. There was need for optimizing the WSP control software for safe and accurate testing possibilities. Therefore, Safeway approached HVR Engineering for measurements, simulations and dynamic FEA of the system.
Simulating Offshore Conditions
Before a gangway is delivered to the customer, a test is performed where offshore conditions are simulated.
Our Approach
The WSP's response during testing not as required. HVR proposed a combination of services to understand what caused this behavior.
Measurement and Simulation
The first step was to install a measurement system and take a series of measurements to understand what was happening when gangways were tested.
The existing control algorithms of the drive system were running during the first set of measurements. The cycles of testing ran through various periods of the sinus motions as well as with different amplitudes of the sinus motions.
Analysis of the measurement data and basic simulations showed that by redefining some parameters of the controller the control process could be improved and the operation of the WSP was made smoother.
Finite Element Analyis
After the controller of the WSP was improved, FE Analysis were used to perform several strength analysis of the WSP.
During FE Analysis, not only the structure of the WSP was analysed, but also the test-and-transportation frames of the latest Safeway Gangway. The goal of the FE Analysis was to determine the strength of the structures and simultaneously determine the limitations of the WSP while testing the gangways under different angles and variations.
Strength assessment
One of the conclusions from the ULS and FLS analysis, was that the test frame of one of the gangways was too flexible for the foreseen application.
The flexibility of the test frame would result in excessive stresses on the Wave Simulation Platform structure. As a solution, HVR Engineering proposed structural changes to the test frame. Additional FE Analysis of the upgraded structure was applied to determine the structural limitations of the WSP for testing. Safeway could then use limitations in their test procedures.
Gangway testing
Our analysis allowed Safeway to safely run the tests of their latest gangway on an upgraded Wave Simulation Platform with a modified test frame.
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