Do They Really matter?

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The Short answer is YES they do.A section exposed to dynamic influences will experience drag induced forces.Based on Hydrodynamics the formula for Drag is defined as:

Where:

As area is directly related to diameter we would expect the diameter to influence resulting drag forces

Simple Explanation

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Plastic System OD : 400mm

CPNL System OD : 260mm (Max)Area of Drag for 4m Length : 1.6m2

Area of Drag for 4m Length : 1.04m2

Reduction in Drag Area of 35%

400mm

260mm

The Result

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From the equation, the resulting drag force is directly proportional to the area exposed to moving fluid.

Water Velocity (kts)

Dra

g Fo

rce

(kgF

)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Plastic System

CPNL System

Figures based on force applicable on a 4.3m length cylinder

Conclusion

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A larger OD diameter will increase forces associated with Drag, vs a smaller OD System.

These systems require thicker walls, which increase thermal insulation of the power cable

The increase in forces invariably results in a need for additional material to prevent failure.

More material, results in higher likelyhood of issues during plastic production process, not to mention cost.

These increased forces will be present throughout the lifetime of the system, but cannot be designed out in a plastic system due to material limitations.