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Class: Pipe

Description

The Pipe class represents a straight section of a process pipeline.
It encapsulates geometry (diameter, length), material properties (roughness), and state (inlet/outlet pressure).
This class is central to flow and pressure drop calculations and is compatible with optimization workflows.

Initialization

Pipe(
    name: str,
    nominal_diameter: Optional[Diameter] = None,
    schedule: str = "STD",
    material: str = "CS",
    length: Optional[Length] = None,
    inlet_pressure: Optional[Pressure] = None,
    outlet_pressure: Optional[Pressure] = None,
    internal_diameter: Optional[Diameter] = None,
    flow_rate: Optional[VolumetricFlowRate] = None,
    **kwargs: Any
)

Parameters - name (str): Unique name of the pipe.
- nominal_diameter (Optional[Diameter]): Nominal pipe size, a label: the NPS (Diameter(4, "in")) or the DN in millimetres (Diameter(100, "mm"), which is NPS 4). The internal diameter is looked up for schedule in the ASME B36.10M / B36.19M table. If neither diameter is given, the pipe is considered a candidate for optimization.
- schedule (str, default="STD"): Pipe schedule ("STD", "XS", "40", "Sch 40", "40S"...). ValueError if it is not tabulated for the nominal size.
- material (str, default="CS"): Pipe material.
- length (Optional[Length]): Pipe length. Defaults to 1.0 m if not provided.
- inlet_pressure (Optional[Pressure]): Inlet pressure of the pipe.
- outlet_pressure (Optional[Pressure]): Outlet pressure of the pipe.
- internal_diameter (Optional[Diameter]): The bore used in the calculations. Given with nominal_diameter, it replaces the tabulated bore (a lined pipe, a non-standard wall) and must be smaller than that size's outside diameter (ValueError otherwise).
- flow_rate (Optional[VolumetricFlowRate]): Initial flow rate for solver. Defaults to 0.001 m³/s. The engine does not size or solve from it: a network pipe is sized for the flow it carries in the network.
- **kwargs (Any): Additional custom parameters stored in the base class.

A diameter or length given as a bare number is read in metres, as before, with a UserWarning; pass Diameter and Length objects. A nominal_diameter that is not a standard size is used as the internal diameter, with a UserWarning. Pipe has no diameter input: Pipe(diameter=...) is ignored (kept in params), with a UserWarning.

Attributes - is_optimization_target (bool): Whether this pipe is flagged for optimization (true if no diameter was provided).
- nominal_diameter (Optional[Diameter]): Nominal pipe size, as the NPS (a DN input is stored as its NPS).
- schedule (str): Pipe schedule.
- material (str): Pipe material.
- length (Length): Pipe length.
- roughness (Variable): Material roughness (from standards).
- internal_diameter (Optional[Diameter]): Internal diameter (the bore every calculation uses).
- inlet_pressure (Optional[Pressure]): Inlet pressure.
- outlet_pressure (Optional[Pressure]): Outlet pressure.
- flow_rate (VolumetricFlowRate): Flow rate through the pipe.
- start_node (Optional[Any]): Start node (set externally in networks).
- end_node (Optional[Any]): End node (set externally in networks).

Methods

cross_sectional_area() Returns the internal cross-sectional area of the pipe.

Returns:
- Variable: Area in square meters (m²), or None if no internal diameter is defined.

surface_area() Returns the external surface area of the pipe, on the outside diameter of the nominal size.

Returns:
- Variable: Surface area in square meters (m²), or None if no nominal diameter is defined.

pressure_difference() Computes the pressure difference between inlet and outlet.

Returns:
- Pressure: ΔP = Inlet - Outlet, or None if pressures are not defined.

to_dict() Exports all key pipe data as a dictionary.

Returns:
- Dict[str, Any]: Dictionary of all pipe attributes and calculated values.

calculate() Compatibility hook for PipelineEngine. Returns the pipe data dictionary.

Returns:
- Dict[str, Any]: Same as to_dict().

Examples

from processpi.pipelines.pipes import Pipe
from processpi.units import Diameter, Length, Pressure, VolumetricFlowRate

# Create a pipe with specified dimensions and pressures
pipe = Pipe(
    name="P-101",
    nominal_diameter=Diameter(4, "in"),   # NPS 4, STD bore 102.26 mm
    length=Length(5.0, "m"),
    inlet_pressure=Pressure(3.0, "bar"),
    outlet_pressure=Pressure(2.8, "bar"),
    flow_rate=VolumetricFlowRate(0.01, "m3/s")
)

print(pipe.cross_sectional_area())
print(pipe.pressure_difference())
print(pipe.to_dict())