Many systems contain both compressors and control valves, which makes the sizing process somewhat more complex.

Like sizing pipes and compressors or pipes and control valves concurrently, there are adjustments and estimations that must be made when sizing all three in parallel. The overall goal and considerations that must be taken into account are described in detail in those topics and will not be repeated here. Only the outline of steps will be presented for brevity.

Process Outline

1. Find the Approximate Compressor and Control Valve sizes

   1. Model the compressor(s) with the Compressor Sizing option, fixing the flow to the desired amount.

   2. Model the Control Valve(s) with the appropriate settings.

      1. If the control valve(s) are Flow Controls downstream of the compressor(s) to be sized, temporarily set them to be Pressure Drop Control Valve with a setpoint equal to the minimum required pressure drop.

      2. Any non-Pressure Drop control valves will require a Design Requirement of minimum dP/dH or maximum C_v/Open Percentage.

   3. Add the compressor(s) and control valve(s) to one or several Engineering Libraries.

      1. Attach a Cost Library to each Engineering Library if one does not already exist.

      2. Create a Power vs. Cost Scale Table for the compressor with estimated cost values.

      3. Create a C_v vs. Cost Scale Table for the control valve with estimated cost values.

   4. Select the appropriate options in the Sizing Window.

      1. The cost for the compressor(s) and control valve(s) will only be included in the Objective if it is specified to be included in Size/Cost Assignments.

      2. If there are several compressors or control valves that will ultimately be of the same type, they should be placed into Maximum Cost Groups.

   5. Run ANS.

      1. Investigate the resulting compressor size.

      2. Update the Nominal Efficiency and NPSHR based on the result. Also update the cost information if necessary. If the compressor accounts for a large portion of the overall cost, accurate values here are more important.

      3. Repeat the process as necessary, until reasonable estimates for cost at the resulting operating point are obtained.

2. Compare Candidate Compressors

   1. Locate accurate cost information and compressor curves for the candidates.

      1. Incorporate these values into Engineering and Cost Libraries.

   2. Compare the sizing results for each candidate compressor.

3. Select the two or three best candidate compressors and compare candidate Control Valves.

   1. If necessary, change Pressure Drop Control Valves back to Flow Control Valves.

      1. This will require a Design Requirement of minimum dP/dH or maximum C_v/Open Percentage.

   2. Locate accurate loss and cost information for the candidate control valves.

      1. Incorporate these values into Engineering and Cost Libraries.

   3. Compare the sizing results for each candidate control valve, under each candidate compressor.