When to Break a Pipeline into Segments

There are four reasons for breaking a pipeline into multiple segments.  

  • The pipe diameter, pipe specification, or fluid zone changes
  • The flow branches from a single pipeline into multiple pipelines, or converges from multiple pipelines into a single pipeline
  • To obtain a pressure at a given location in the piping system
  • To connect to a pump, component or control.

In a PIPE-FLO drawing a pipeline can have multiple vertices, or multiple line segments to represent a single pipeline.  There is no need to draw multiple pipelines simply to have an orthogonal drawing.  This feature allows you to make the PIPE-FLO drawing look more like a flow sheet or Piping and Instrumentation Drawing (P&ID).

Figure 1. In PIPE-FLO a single line can have multiple vertices and line segments.  There is no need to create multiple pipelines just to have vertices in a pipeline.

Changing Pipeline Diameter, Pipe Specification or Fluid Zone
A new pipeline must be created when the pipe diameter, specification, or fluid zone is changed.  For example in Figure 2 below there are four pipelines.  PIPE-001 is 4 inches in diameter, since PIPE-002 is 6 inches in diameter a new pipeline must be created.  PIPE-002 is built to Specification 01 and uses steel schedule 40 pipe, since PIPE-003 uses steel schedule 80 pipe, specification 02 was created, resulting in a new pipeline.  PIPE-003 has Water at 60F as the process fluid, since the fluid in PIPE-004 is Water at 100F, fluid zone 02 was created resulting in a new pipeline.

Figure 2. In PIPE-FLO a new pipeline must be created with the pipe diameter, specification or fluid zone changes.

Branching Flow
When the flow branches from a single pipeline into two or more pipelines, multiple pipelines are required. In practice three pipelines are connected by way of a tee, and four pipelines can be connected by way of a cross.

Note:  PIPE-FLO does not automatically insert a Tee-Branch or Tee-Run fitting when connecting multiple pipelines to a node. You can add these fittings in the Valve & Fitting tab of the Pipeline design dialog box.

Calculating Pressure
PIPE-FLO calculates the pressures only at a pipe junction or node.  If you need to determine the pressure at a specific location then you must insert a node at that location.  

Figure 3 below show the importance of knowing the pressure at a mid point in a pipeline.  The system consists of a suction pipeline, a pump and discharge pipeline. The pump suction and outlet tanks are both at 0 ft. elevation. The discharge pipeline is 500 feet long with a high point elevation of 60 ft.  

Figure 3. Inserting a junction at a high point is recommended to insure the piping system will operate as designed.

The top example does not have a node at the highpoint; as a result PIPE-FLO is not able to calculate the pressure at this location.  The system appears to be operating properly.  

The bottom example breaks the discharge pipeline into two segments with 400 feet in pipe discharge 1a and 100 feet in pipe discharge 1b.  The High Point is located at an elevation of 60 ft.  As you can see by the results on the FLO-Sheet, the pressure of "–22.05 psig" is well below the vapor pressure of the fluid.  As a result flashing will occur in the pipeline and the system will not operate properly.  

Connecting Pumps, Components, and Controls
When modeling a system in PIPE-FLO, you can place the object on the FLO-Sheet first, then draw and design the interconnecting pipelines.  This greatly simplifies the design process.  This also allows you to specify an elevation for pumps, controls, and components, so PIPE-FLO can calculate the inlet and outlet pressure for these devices.  Figure 4a shows a piping system with the components place on the FLO-Sheet.  When these devices are placed you must enter a name, elevation for the items, along with a set value. 

Figure 4a. Placing the object on the FLO-Sheet prior to designing the pipelines streamlines the design process.

When you design the connecting pipelines to the various objects, the pipeline end point elevations are taken from the placed objects, eliminating the need to re-enter the elevations when designing the pipelines.

Figure 4b. The Interconnecting pipelines are drawn to the components but are not designed.