- Drag reducing agent
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A drag reducing agent, also called a flow improver, is a long chain polymer chemical that is used in crude oil, refined products or non-potable water pipelines. It is injected in small amounts (parts per million) and is used to reduce the frictional pressure drop along the pipeline's length.
The benefits of using a drag reducer are the following
- Increase in pipeline throughput
- Reduction of the waiting time for tanker loading/offloading
- Maintaining the throughput during MOL (Main Oil Line) pump maintenance for de-rated lines
- Bypassing MOL pump stations
- Energy Savings
The chemicals damp turbulent bursts of the oil near the pipeline wall, that way less disturbance is created during the oil flow. Minimizing turbulence in the radial direction better preserves flow in the axial direction of the pipeline.
Drag reduction effectiveness for a given concentration is based on the turbulent characteristics of the pipeline. The maximum theoretical effect is the same as a pipe in laminar flow, where all of the turbulence is eliminated by the agent. Drag reduction effectiveness is measured as a percentage of the pipeline with no DRA present. For example, 75% drag reduction is representative of a pipeline that has one quarter of the frictional pressure loss at a given flow rate.
Since DRA is composed of long polymer strands, it is prone to degradation as it travels through the pipeline due to shearing of the strands. Large pressure changes through a control valve or pump result in a total loss of effectiveness. DRA may be reinjected after such equipment, but the total injection is usually limited by the product specifications or fluid limitations. DRA should never be used with any turbine fuels (such as jet fuel) because the polymer will accumulate on turbine blades and may damage the turbine.
Drag reducers were invented more than 30 years ago by Conoco Inc. (now ConocoPhillips). Its use has allowed pipeline systems to greatly increase in traditional capacity and extend the life of existing systems. The higher flow rates possible on long pipelines have also increased the potential for surge on older systems not previously designed for high velocities.
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