Priming, foaming and carryover

PRIMING, FOAMING AND CARRYOVER

1. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
PRIMING, FOAMING AND
CARRYOVER

2. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
Priming
Priming means carryover of water particle in the steam which lowers the energy
efficiency of the steam and leads to scale formation at superheater and in the
turbine blade. Priming may be caused due to the following reasons:
• High water level
• Foaming of feedwater
• Sudden fluctuation in steam demand
• High impurities concentration in the boiler water
• Improper construction of the boiler
High water level is the common cause of priming. To avoid priming, high water
level, excessive boiler load and sudden load change should be avoided

3. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
Carryover
During carryover, contaminant leaves a boiler steam drum with the steam. It can
be in solid, liquid or gaseous form. It is undesirable in a boiler. Some of the effects
of carryover are mentioned below:

• Deposition in regulating and controlling valves
• Deposition in superheater
• Deposition in servomotor control valves and turbine blade
• Process contamination

4. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
Carryover
Carryover is due to the incomplete separation of steam from the steam–water
mixture in the boiler drum. Steam separation units are placed inside the boiler
drum. Defects on these separation units may lead to carryover. Foaming of boiler
water is also responsible for carryover. Boiler design, type of mechanical steam
separating equipment, load fluctuation, boiler drum level, amount of space
available for steam separation from the steam–water mixture are some of the
causes of carryover.

5. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
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. When these bubbles burst, moisture is
entrained with the steam. Some of the causes of foaming are given below:

• High dissolved solid concentrations in the boiler water
• High suspended solid concentration
• High alkalinity concentration
• Oil and organic contaminants in the boiler water

6. Md.Arifull Hoque Shaheen
Jr.Assistant Manager (chemical)
410MW CCPP Bheramara,Khustia
Bangladesh.
Thank you