We were asked to verify whether a three-meter diameter Glass Reinforced Plastic (GRP) ductwork was fit-for-purpose. Using the industry-standard software, CAESAR II, we created a pipe stress analysis model to provide an understanding of how the system was behaving (and why it wasn’t meeting the requirements). The analysis indicated areas where the duct was overstressed. We provided recommendations for design modifications to reduce stress concentration factors and so to prevent damage to the duct ensuring the system didn’t fail and saved money on repairs.
PDL supported our clients, mechanical and material engineering experts who offer a wide range of services around inspection and testing to provide a comprehensive understanding of the condition of their client’s assets. We verified whether a three-meter diameter GRP ductwork for a Bio-filter system, under vacuum, for a wastewater treatment plant, was fit-for-purpose.
Using the industry-standard software, CAESAR II, we created a pipe stress analysis model to represent the duct to assess its integrity and provide an understanding of how the system was behaving (and why it wasn’t meeting the requirements). The model was designed to consider the effect of the vacuum, expansion due to solar radiation and wind loads all in line with the GRP stress code, BS 7159:1989. The thermal loading profile due to solar radiation was developed using our heat transfer calculation tools.
Working closely with our client, the first phase of the work looked at assessing previous analysis work done. We pinpointed particular errors in the modelling and flaws in the assumptions made. Following this review, we then proceeded to build a more accurate 3D representative model which covered vacuum pressure, duct diameters, duct thicknesses, design temperatures, material specs, restraint types and locations and expansion joint specifications of the GRP duct. Additional information around material properties, stress intensity factors and particular loading were taken from the pipe code ASME B31.3, material databases and other data references. The analysis covered a variety of operational cases, and the model was used to extract support loads, nozzle loads at filters and fans as well as the duct displacements. Through the analysis, our engineers were able to provide accurate results for the duct under wind loading and solar radiation. The analysis indicated areas where the duct was overstressed. We were then able to provide recommendations on design modifications to reduce stress concentration factors and so to prevent damage to the duct.
- Greater understanding of the system to increase performance and how best to repair it.
- Stopped all minor repair work saving time and money towards long-term maintenance.
- Prevented failure of the system.