Chemical Engineering Interview Question:

Are there flow velocity restrictions to avoid static charge build up in pipelines?

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There is an Australian standard "AS1020 (1984) - Control of undesirable Static Electricity" In it, there is a table for flammable hydrocarbons as follows:

Pipe Size (mm) Max Velocity (m/s)

10 8

25 4.9

50 3.5

100 2.5

200 1.8

400 1.3

600+ 1.0

This is based on pure hydrocarbons, and there is a correction, which can be applied for fluids of different conductivity. Methanol has a higher polarity than hydrocarbons and hence is more conductive. The resistivity of diesel is 1013 ohm-m vs 108 for methanol. In addition to this, normal piping design guidelines should however be followed, such as appropriate earthing, and ensuring exit velocities into tanks of 1 m/s.
Submitted by: Administrator