Calculate boiler blowdown rate from steam output, feedwater TDS and boiler-water TDS limit, or solve for the supported steam rate or maximum feedwater TDS.

Estimate continuous blowdown from steam generation and dissolved solids.

Use boiler feedwater, including condensate return; not make-up water alone.

Use the boiler maker’s limit. ABMA guidance for 0–300 psig drum boilers is about 3,500 ppm.

Daily operating time
Blank means 24 hours. Used only for daily discharge.

Boiler Blowdown Rate Formula

The following formula is used to calculate the Boiler Blowdown Rate. 

BBR = SC × TDSW / (TDSM - TDSW)

Variables:

  • BBR is the Boiler Blowdown Rate (kg/h)
  • SC is the steam consumption (kg/h) 
  • TDSW is the total dissolved solids in the water (ppm) 
  • TDSM is the maximum allowable dissolved solids (ppm) 

To calculate the boiler blowdown rate, multiply the steam generation rate by the feedwater TDS, then divide by the maximum boiler-water TDS minus the feedwater TDS. The maximum must exceed the feedwater TDS. Select a solve mode, enter the required values and units, then select Calculate. In Daily operating time, blank hours means 24 hours; this setting affects daily discharge only. Use the boiler manufacturer’s water-quality limits.

How to Calculate Boiler Blowdown Rate?

The following steps outline how to calculate the Boiler Blowdown Rate.

  1. First, determine the steam consumption (kg/h).
  2. Next, determine the total dissolved solids in the water (ppm). 
  3. Next, determine the maximum allowable dissolved solids (ppm). 
  4. Next, gather the formula from above: BBR  = SC * TDSW / (TDSM-TDSW).
  5. Finally, calculate the Boiler Blowdown Rate.
  6. After inserting the variables and calculating the result, check your answer with the calculator above. 

Example Problem:

Use the following variables as an example problem to test your knowledge.

steam consumption (kg/h) = 50

total dissolved solids in the water (ppm) = 20

maximum allowable dissolved solids (ppm) = 30

BBR = 50 × 20 / (30 − 20) = 100 kg/h