Crude oil is supplied via pipelines from the storage tanks in Rotterdam to various customers in Europe. One of the pipelines had to be replaced at two locations, making it necessary to take the pipeline out of operation for a short period of time.
Based on TECCURO’s experience and in collaboration with the customer the risks of the operation were challenged during the engineering phase. To empty and fill the pipeline in a safe, fast and above all environmental friendly way all the mitigating measures have been incorporated into an action plan. To lower the risks, it was decided to carry out each replacement separately.
During the first project, the last 3 kilometres of the pipeline was emptied with gaseous nitrogen. To do this, two special prepared pigs were launched from Rotterdam and sent with the oil towards a predetermined valve. One of the pigs was positioned upstream of the valve, while the other pig was positioned downstream. Through an hot tap connection the first pig was moved with nitrogen to the pig receiver at the end of the pipeline. A liquid-gas separator was used to prevent that nitrogen would bypass towards the customers (who are not able to process large quantities of gas). The separator ensured that the gas mixture (nitrogen with hydrocarbons) is separated from the oil. The gas mixture was released into the atmosphere through an active carbon filter. The active carbon filter consists out of adsorption material which is able to bind the hydrocarbons. As a result, there has been no emissions released towards the environment. To ensure that the filter wouldn’t become saturated, continuous measurements have been done. As a precaution, extra filter capacity has been placed to provide the possibility to replace the filters without losing time. However, this was not necessary. The collected oil in the separator was removed via a vacuum truck with a gas washing installation and brought to one of the customers.
When the pipe was depressurized and secured, the mechanical contractor started to cut and remove the pipeline section. After reconnecting the new pipe, TECCURO completed the commissioning of the pipeline.
The second project was carried out in almost the same way. The difference was the location of the pipe section that need to be emptied, which was located in the middle of the pipeline. The oil of the section was pushed through the existing pipeline towards the customers by using high friction pigs and gaseous nitrogen. In this way TECCURO was able to clear a section in the middle of the oil pipeline without any risks to the environment. As in the first project, the nitrogen was depressurized via active carbon filters. Because the oil remained in the pipeline, the liquid-gas separator was not needed.
After the mechanical works of the 250 meter pipeline section was completed, the line was ready for commissioning. By using the oil in the pipeline the second pig was slowly moved towards the first pig. Through a temporary connection, the gaseous space between the two pigs was filled with water. The water ensures that the pigs couldn’t run into each other and the customers will not receive too much gas in their product. After the pigs were received in the pig receiver at the end of the pipeline, the line was fully operational.
Due to extensive preparation and cooperation with all parties involved, both projects were carried out well within the short period of time.
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