The client determined that the vessel maximum allowable working pressure (MAWP) was bottlenecking the system decreasing the efficiency of its processes. Assistu was requested to determine if their vertical separator could be re-rated.

The vessel was constructed in 1975 and had no history of any failures or repairs. Since the original calculations could not be produced, a new set of calculations was created. Using the original code of construction and the current edition, the more conservative values were used to produce the reports. This was necessary to reduce the risk of failure due to the original code of construction used and the age of the vessel. Based on the calculations some of the nozzle reinforcement pads had to be removed and upgraded to meet the required area of reinforcement. Assistu provided design drawings to modify the existing vessel. Additional to this, a thorough inspection was performed to evaluate the current condition of the vessel. This included NDE to be performed based on the known damage mechanisms. The vessel had no flaws reported.

Did you know? In Alberta, a Fitness for Service and re-rate cannot be performed at the same time.

It took about 6 weeks to evaluate the vessel (this includes inspection and submission to the regulator). Assistu concluded that the vessel was safe to operate at the proposed re-rate pressure and the submission was accepted by the regulator.