Table of Contents
Why does a boiler blow off?
Boiler blow down is done to remove carbon deposits and other impurities from the boiler. Blow down of the boiler is done to remove two types of impurities – scum and bottom deposits. This means that blow down is done either for scum or for bottom blow down.
What is meant by blowdown process?
Blowdown is the removal of water from a boiler with the help of a blowdown valve. This valve removes the dissolved solids in the boiler water through the boiler exit port. Blowdown is also associated with heat exchangers or cooling towers in the industrial processes which use water.
What is the purpose of blow down?
Blowing down is a process which involves draining a small amount higher hardness and solids water from the boiler and replacing it with lower hardness and solids makeup water to maintain a predetermined concentration of hardness and solids.
What are the types of blowdown?
There are two main types of boiler blow down, surface blow down and bottom blowdown.
- Bottom Blowdown: As its name suggests, this function happens at the bottom of the boiler commonly known as the mud drum.
- Surface Blowdown: Happens near the surface at the location where the concentration of dissolved solids is highest.
How does a boiler blowdown work?
Boiler blowdown is water intentionally wasted from a boiler to avoid concentration of impurities during continuing evaporation of steam. The water is blown out of the boiler with some force by steam pressure within the boiler.
What is a boiler blowdown valve?
Blowdown valves are useful in fossil fuel fired boilers for continuous or intermittent use to drain dissolved solids from the boiler water. These valves are fitted on the drain lines of the boilers.
What is a boiler blowdown tank?
A blowdown tank is designed to collect the intermittent blowdown from the bottom blow off connections (or mud drum) and from the surface blow off connections. The blowdown tank provides a safe method of collecting the water which is removed from the boiler during blowdown.
How does a boiler blowdown vessel work?
When should I blow my boiler down?
A boiler is blown down to control the amount of solids and sludge in the boiler water. An excessive amount of solids and sludge can insulate the heating surfaces on the waterside of the boiler. The metal overheats, and as a result, the pressure vessel fails.
What is boiler blowdown rate?
Rate of blowdown is a rate normally expressed as a percentage of the water feed. In the case of boilers, rate of blowdown is the removal rate of water from a boiler. Its purpose is to control boiler water parameters within prescribed limits to minimize: Scale. Corrosion.
How is blowdown rate calculated?
The optimum blowdown rate is determined by various factors including the boiler type, operating pressure, water treatment, and quality of makeup water. Blowdown rates typically range from 4\% to 8\% of boiler feedwater flow rate, but can be as high as 10\% when makeup water has a high solids content.
How does a blowdown valve work?
Continuous Blowdown (CBD) valves are designed to operate in continuous open position by releasing water continuously through a blowdown tap near the boiler water surface, thereby maintaining the TDS level in the boiler drum.
What is a Surface blowdown on a boiler?
Surface blowdown Surface blowdown continuously bleeds off a low volume of water from within the boiler as a means of ridding the boiler of dissolved impurities. It is most effective to remove water with the highest level of impurities; and such water is found where steam separates in the steam drum at the top of the boiler.
How do you blow down a gas boiler?
Blow down the boiler for the amount of time specified by your water management consultant by opening and then closing the slow-opening valve. Pay close attention to the water level in the gauge glass. Some loads require several, short blowdown cycles to maintain the proper water level in the boiler.
Can water blowdown be used to heat process streams?
If economically justified, boiler water blowdown can be used to heat process streams. In most cases, boiler water blowdown heat recovery systems use flash steam from the flash tank for deaeration. The blowdown from the flash tank is passed through an exchanger and used to preheat boiler makeup water.
What causes water to blow out of the boiler?
The water is blown out of the boiler with some force by steam pressure within the boiler. Bottom blowdown used with early boilers caused abrupt downward adjustment of boiler water level and was customarily expelled downward to avoid the safety hazard of showering hot water on nearby individuals.
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