Reasons for Priming, Foaming and carryover in Boilers

 

Priming:

1. What do you mean by the term Priming?

Priming means carryover of water particle in the steam

2. What are the reasons for Priming?

Reasons for priming;

  • Improper design of Boiler and steam drum
  • Maintaining high drum level
  • Boiler load fluctuation
  • Sudden load raise due to steam demand
  • Foaming in feed water
  • Miss operation of Boiler
  • Sudden lifting of Boiler safety valve or start up vent CV
  • More impurities in Boiler water

3. What are the impacts of Priming?

Impacts of Priming;

  • Lower steam efficiency
  • Water hammering
  • Super heater coil failure due to thermal shock
  • Turbine high vibration & blade failure

How do you avoid priming in Boilers?

Priming can be avoided by;

  • Proper operation of boiler
  • Maintaining drum level in between 45 to 55%
  • Avoiding foaming
  • Avoiding sudden load fluctuation
  • Proper designing of Boiler

Carryover:

What do you mean by the term carryover?

Carryover is the carryover of solid, liquid & gaseous contaminants with water and steam leaving the drum due to incomplete separation of water and steam in steam drum.

What are the major reasons for carryover?

Reasons for carryover;

  • Defects in steam and water separators
  • Foaming
  • Boiler load fluctuation
  • Higher drum level
  • Boiler steam drum construction defects

What are the effects of carryover on Boiler components?

Contamination in steam leads to deposition of solid scale on Super heater coils & control and regulating valves.

Foaming:

What do you mean by the term foaming?

Foaming is the formation of unbroken bubbles on the surface of the boiler water inside the boiler drum.

The bubbles may be in thin layer with few bubbles overlying each other or it may build up throughout the steam space.

What are the reasons for foaming?

  •  High suspended solid concentration
  •  High alkalinity concentration
  •  High dissolved solid concentrations in the boiler water
  •  Oil and organic contaminants in the boiler water
  • High impurities
  • High dosage of chemicals
  • High water level

How do you avoid foaming?

  • Timely blow down & maintaining desired water quality
  • Maintaining constant load on Boiler
  • Avoiding high water level
For more articles read Power plant and calculations

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