Context
Generalities
The piping slope is the change in elevation with respect to its flat horizontal position. The piping slope is provided in various piping systems mainly due to free-draining requirements. A slope in the pipe helps the liquid to flow easily in the downward direction. So, it helps in avoiding the accumulation of liquid inside the piping system. This in turn helps the system to eliminate two-phase slug flow problems.
- Underground drain piping
- Condensate piping system
- Drains and vents
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The value of the piping slope required is usually decided by the process engineers following industry experience and thumb rules. Some of the thumb rules that are prevalent in the process industry are listed below:
- All piping in the main steam and hot and cold reheat line, turbine extraction system, condensate system, and turbine drains, of power plants are sloped down a minimum of ¹⁄₈ in/ft (10 mm/ m), in the direction of flow.
- It is common practice to design sanitary sewers with slopes sufficient to provide for velocities of 2 ft/s (0.6 m/s) when flowing full. Experience shows that with such slopes, trouble from deposits is seldom encountered
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Piping Schemes (PFD / P&ID)
As slope are defined by the process engineer, it would make sense that this information is appearing in the P&ID either as a value of the piping line or at minimum as a symbol in the Scheme.
Having this information + having pipe length estimation will help to do calculation on early design phases
Piping 3D design
The slope will be realized in 3D (and in the shopfloor) in 2 different ways
- by using/assemble standard components (elbows, branches) that are made to ensure a given slope (angle are different from 90deg). typically used for threaded or socked connection
- by using/assemble standard components (elbows, branches) with 90deg angle but that have an allowed tolerance because of the flexibility of the connection that used integrated rubber gasket
- by using/assemble standard components that are modified/cut at shop floor and welded
Finally, at the end, after 3D design is done, slope information must be reported into the fabrication/assembly piping drawing , especially into the piping Isometric
