Sizing Components Other Than Pipes

Sizing Pumps

While pumps are not directly sized by ANS, they are able to be indirectly sized by including an estimation of their cost. Their actual behavior is a result of the system. The appropriate sizing of a pump requires a Cost Library and understanding of standard Pump Sizing.

At the most basic, pump sizing is simply selecting a pump that is capable of meeting pressure and flow requirements. Too often this involves selecting a pumps that is larger than required, under the assumption that a bigger pump will provide for operational margin. Unfortunately, over-sizing a pump has negative impacts on reliability and efficiency, both of which incur higher cost. Over-sizing could also require the installation of ultimately unnecessary valves or restrictions to bring the flow back down to where it should be.

The ability to appropriately size pumps is built into AFT Fathom. By using the Pump Sizing option, AFT Fathom will indicate the amount of head required to deliver the specified flow. It is up to the user to find a pump that operates at its BEP at the calculated flow and head.

The best size of pump to use when the pipe sizes are allowed to change as well is harder to handle, and requires iteration. See Sizing Pipes and Pumps Concurrently.

Note: Certain pump configurations require special attention in ANS. See Special Concerns For Sizing Pumps.

Sizing Control Valves

Control Valve sizing is similar - AFT Fathom already has all of the tools needed to size a Control Valve for a specific set of pipes. AFT Fathom will report the Cv or K Factor necessary for a Control Valve to attain a given setpoint. From this value, an appropriate valve could be selected for minimizing cost. It would be typical to select the smallest Control Valve possible while still remaining in a good control range - typically 20-80% open.

Like pumps, selecting the best Control Valve while pipe sizes are changing is more complex. See Sizing Pipes and Control Valves Concurrently.

Sizing Other Junctions

Any other junction can be included in the sizing process as long as cost data exists.

For example, a Bend can have costs associated with it via a Table of Costs. From this table, ANS can determine the cost for a given diameter. ANS will assume that the Bend is of a diameter equal to the upstream pipe inside diameter, and include the corresponding cost in the Objective. If certain components are very expensive compared to piping, this could affect the selection of pipe sizes.

Sizing Ducts

Duct sizing has special considerations discussed in Sizing Duct Systems.