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Influence of drag reducing agent on measurement performance

The use of drag reduction agent (DRA) in oil pipelines is a way to save energy but long-chain polymers can have an influence on the pipeline metering system. Consequently the aim of the project is to analyse the effect of drag reducer agent on the metering equipment under different operating conditions and to determine the less energetic method based on line equipment to destroy this influence.

Tests are based on a comparison between two counters: one at the beginning of the line located before the injection point and a second at the end. The first one is the reference counter because, during the tests, it is never influenced by the long-chain polymers of the drag reducer agent. The second one is the tested one on which deviation is measured.

Each test was composed by a series of different stages but always began by a stage of reference: comparison of both counters without DRA injection. The following steps could be done one after one or separately:
- Test of influence: line full of additived fuel in normal use conditions (NB: control valves after injection point of long-chain polymers have to be fully opened).

- Test of destroying effect: line full of additived fuel with addition and before the second counter, set up of the tested method to destroy effect of long-chain polymers on the measuring system.

Tests of influence on helicoidal blades turbine metering system show that counters over count when drag reducer agents are used (deviation depends on the concentration of the additive and can reach five per mil at 25ppm injection rate).

To destroy the deviation effect, the best way is the use of control valve to create a pressure drop before the downstream metering equipment. At 5 bars of pressure drop no more influence is noticed. The pressure drop value could be under 5 bars if the installation is composed by elements, which create pressure drop on their own.

Pump is another way to destroy effect but should be used only if after the pump there is another section of pipeline (that does not need DRA) as pump itself needs energy to work and that energy is lost in case of delivery just after this equipment.

Note: A little part energy is saved in using drag reducer agent must be spend to destroy the generated effect on metering equipment.

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Chemin de Maupas
38200 Villette de Vienne
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