Correction Factors

Compressed Air Products / How to choose a dryer / Correction Factors

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CORRECTION FACTORS

The following operating conditions must be considered in every project: inlet air pressure, ambient temperature, inlet air temperature and pressure dewpoint. Each operating parameter has a corresponding numerical factor. A simple calculation between the air flow rate and the various factors defines the right dryer model to choose.

HOW TO FIND THE AIR FLOW CAPACITY?

Air flow capacity =

Nominal duty x (Factor F1 x Factor F2 x Factor F3 x Factor F4)

Example: An ACT 18 has a nominal duty of 108 m3/h. What is the maximum allowable flow through the dryer under the following operating conditions?

  • Inlet air pressure = 8 barg Factor (F1) = 1.05
  • Ambient temperature = 45°C Factor (F2) = 0.72
  • Inlet air temperature = 50°C Factor (F3) = 0.59
  • Pressure DewPoint = 10°C Factor (F4) = 1.37

Each item of data has a corresponding numerical factor which multiplied by the design air flow is as follows:

Air flow capacity = 108 x 1.05 x 0.72 x 0.59 x 1.37 = 66 m3/h

66 m3/h This is the maximum flow rate that the dryer can accept under these operating conditions.

HOW TO SELECT A SUITABLE DRYER FOR A GIVEN DUTY?

Minimum std. air flow rate =

Design air flow ÷ (Factor F1 x Factor F2 x Factor F3 x Factor F4)

Example: With the following operating parameters:

  • Portata d’aria richiesta = 100 m3/h
  • Design air flow = 100 m3/h
  • Inlet air pressure = 8 barg Factor (F1) = 1.05
  • Ambient temperature = 45°C Factor (F2) = 0.72
  • Pressure DewPoint = 10°C Factor (F4) = 1.37

In order to select the correct dryer model the required flow rate is to be divided by the correction factors relating to above mentioned parameters:

Minimum standard air flow rate = 100 : (1.05 x 0.72 x 0.59 x 1.37) = 164 m3/h

Therefore the model suitable for the conditions above is ACT 30 (186 m3/h - nominal duty).