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Resolving piping corrosion and replacement (TIA)

Amec Foster Wheeler provided engineering analysis for a fine tailing treatment project in the Athabasca Oil Sands region in Alberta, Canada.

Vornel Walker
Intergraph Corporation
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Article Summary
The project handles 100 000 b/d capturing the fines from flotation tailings through a thickener. The project equipment included the flotation thickener, the recovered bitumen tank, the overflow water tank and gravity distributor, slurry pumps, the gland water pump and bitumen sump pump.

The 42 inch diameter pipe for overflow water would operate at a temperature of 95°C and a pressure of 2500 KPag. The pipe runs 1000 metres in a common trench with four other pipelines. Normal engineering practice calls for carbon steel (CS) for deep buried piping, but for overflow water service, the service life of CS is only five to eight years due to corrosion. It would be difficult to replace this individual pipe in a common trench with other pipes, entailing huge costs for soil excavation and backfill. To achieve a lifetime operation, fibreglass pipe (FRP) material would be needed.

Calculating shallow-buried pipe stress

Amec Foster Wheeler used Intergraph Caesar II for 56 stress calculations. The FRP overflow line required the UK Offshore Operation Association (UKOOA) design code, one of the many standards included with Caesar II.

Being shallow-buried, the FRP pipe would experience higher movement and greater chance of bend failure plus high thermal movement with all 
changes in direction and at the buried terminal 
points. The engineers input the soil date and FRP configuration into Caesar II to compute the soil 
stiffness in axial, lateral and vertical directions.

To prevent bend over-stress, the engineers recommended installing resilient ethafoam material customised to the bend profile. Using the Caesar II buried pipe modeller, the team input the ethafoam spring rate to calculate the foam stiffness, length and number of layers to make sure the FRP pipe would be safe.

Ensuring data accuracy
With Caesar II’s graphic modelling capabilities, the company avoided a loss of accuracy and design quality that would otherwise pose a problem under such a tight schedule. The team also avoided many wasted hours on analysis that would have been required to address code requirements on such unique and challenging design conditions.

“This would typically require numerous tries, and we would have missed the project deadline without Caesar II,” explained Bhaskar Shitole, piping discipline lead at Amec Foster Wheeler.

“With Caesar II, we saved a lot of time and were able to adjust the foam length to prevent bend overstress. It helped us optimise the design and ensure quality, which in turn saved us in project costs.”

Amec Foster Wheeler received the 2015 Caesar II Runner-Up Drivers of Success Award for its use of the software. The annual competition recognises innovative applications of Intergraph products, impressive project results and significant benefits from collaboration among disciplines and the integration of the products.

This short case study originally appeared in PTQ's Technology In Action feature - Q3 2016 issue.

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