User's Guide on how Drag Reducing Agents work

The first thing to ask when considering the use of DRA's is naturally: Will it do the job?

A good general guideline is to begin by answering two further questions:

• Is the flow in the turbulent region?
• Is most of the pressure loss caused by elbows, flanges, valves or other restrictions in the pipeline system?

DRA's work by linearizing the flow pattern, so the answer to the first question should be yes. In other words, if the flow is not highly turbulent, there is not much DRA's can do.

The second point is important because DRA's are effective in the straight pipe sections of the pipeline system. Actually this is the only part of the total pressure loss is affected by DRA's. That is why you should answer no to the second question.

In practice this means that you must start by evaluating total pressure loss. If you have done that and the answer to the first question is yes and no to the second question, you will most probably gain by using DRA's.

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