1. In order to determine the possible range of operational parameters of the pipeline, a hydraulic analysis should be performed.
2. For a given pipe size, fluid properties and flow rate, the hydraulic analysis should provide the pressure and temperature profiles along the pipeline for steady state and transient conditions.
3. Full account shall be taken of possible changes in flow rates and operational modes, over the complete operational life of the pipeline.
4. The hydraulic analysis should provide data to address: surge pressure during shut-down of a liquid line, turn-down limitations and inhibition or insulation requirements to prevent wax or hydrates deposition, effect of flow conditions on the efficiency of corrosion inhibitors, liquid catching and slug control requirements at the downstream end of two phase lines.
5. The normal range of flow velocities is 1 to 2 m/s in liquid lines, and 5 to 10 m/s in gas lines.
6. Continuous operations above 4 m/s for liquids and 20 m/s for gases should be avoided; lower units may apply to fluids containing solid particles, where maximum velocities will be dictated by the occurrence of erosive conditions.
7. NOTE: Liquid lines containing a separate water phase, even in small quantity (e.g. 1% water cut), should not be operated at too low velocities (typically below 1 m/s). This is to prevent water dropout which may lead to a corrosive situation.
8. For liquid lines, it is sometimes advantageous to adjust the design pressure along the route, depending on the patterns of the hydrostatic pressure and the friction pressure loss.
9. Great care should be applied in the definition of the various sections and associated design pressures to determine whether, under any operations scenario, over pressurisation of one section is possible by the adjacent sections.
10. For gas pipelines, sections of decreasing design pressure are not recommended in general, because the slight cost benefit is unlikely to outweigh the lost advantage of line packing and thus loss of system availability.
