Surface blowdown in boilers is the act of continuously bleeding off a small amount of water from within the boiler to remove dissolved impurities and maintain optimal water parameters.
By regularly performing surface blowdown, boilers can ensure the production of high-quality steam and maintain the longevity of the system.
Surface Blowdown
Surface blowdown in a boiler refers to the removal of water and dissolved impurities, such as salts and minerals, from the surface of the boiler water.
It is conducted from the upper portion of the water level in the boiler drum, where the concentration of dissolved solids tends to be the highest. This process helps to control the levels of Total Dissolved Solids (TDS) in the boiler water, preventing scale formation, corrosion, and carryover of impurities with steam.
Key Features of Surface Blowdown:
- Location: Conducted at the water surface level where dissolved solids accumulate.
- Purpose: Maintains water chemistry within permissible limits to ensure efficient boiler operation and prolong equipment life.
- Controlled Operation: Often performed automatically or semi-automatically based on real-time monitoring of TDS or conductivity levels.
Benefits:
- Prevents the formation of scale, which can reduce heat transfer efficiency.
- Minimizes carryover, where impurities can contaminate steam and downstream equipment.
- Reduces the risk of corrosion caused by high concentrations of dissolved solids.
Proper techniques for surface blowdown
When it comes to performing surface blowdown, certain techniques must be followed to ensure optimal results. The steps involved in surface blowdown include:
- Identify the appropriate location near the surface of the boiler for the blowdown valve.
- Slowly open the blowdown valve to release a small amount of water.
- Monitor the discharged water to ensure it is clear and free from excessive impurities.
- Adjust the blowdown valve as necessary to achieve the desired flow rate and effectiveness.
- Regularly inspect and maintain the blowdown valve to ensure its proper functioning.
By adhering to these proper techniques, the surface blowdown process can effectively remove dissolved solids near the surface and prevent carryover and foaming, contributing to the overall efficiency and longevity of the boiler system.
Why Is Surface Blowdown Important?
- Removing Water to Remove Sediment
- Removing Water to Control Chemical Concentrations
- Removing Water to Eliminate Solids
What Are The Benefits Of Surface Blowdown?
- Prevents the buildup of sludge and sediment
- Maintains optimal boiler efficiency
- Extends the lifespan of the boiler
Best Practices For Surface Blowdown
- Monitor Water Quality Regularly
- Automate Blowdown Where Possible
- Optimize Blowdown Frequency and Duration
- Preheat Feedwater with Blowdown Heat Recovery
- Conduct Regular Water Treatment
- Inspect and Maintain Blowdown Valves
- Balance Surface and Bottom Blowdown
- Follow OEM Recommendations
- Regularly Review and Adjust Practices
FAQ’s Of What Is Surface Blowdown In Boiler?
Why Do We Carry Out Boiler Surface Blowdown?
Boiler surface blowdown is conducted to remove sediment, chemicals, and solids from the boiler water. This helps prevent carryover, corrosion, and scaling, ensuring high-quality steam and a reliable, long-lasting boiler. Surface blowdown removes dissolved solids like sodium, potassium, chloride, and soluble calcium.
What Is Bottom Blowdown In Boiler?
Bottom blowdown in a boiler is the process of removing the sludge that accumulates at the bottom of the boiler during boiling. This is important because unchecked sludge can impact heat transfer systems and lead to tube or vessel failure.
Proper bottom blowdown helps maintain a reliable and efficient boiler system.
How Often Should A Boiler Have A Bottom Blowdown?
A boiler should have a bottom blowdown regularly to remove the sludge that accumulates at the bottom of the boiler. This helps prevent issues like heat transfer system damage and tube or vessel failure. Bottom blowdown is essential for maintaining the efficiency and longevity of the boiler.
References:
- “Avoiding Boiler Problems.” William L. Reeves. ASHRAE Journal. September 2001 Issue.
- “Boiler Blowdown Energy Recovery.” Greg Harrell. Energy Matters Newsletter. Winter 2003 Issue.
Department of Energy. Industrial Technologies Program. 2003. - Boiler Efficiency Improvement. David F. Dyer and Glennon Maples. Fifth Edition. Auburn University.
Boiler Efficiency Institute. Auburn, Ala. 1991. - “Best Practices – Steam Generation.” Utah Industries of the Future.
- “Install an Automatic Blowdown Control System.” Steam Tip Sheet #23. Department of Energy. Industrial
Technologies Program. April 2004. - “Minimizing Boiler Blowdown.” Steam Tip Sheet #9. Department of Energy. Office of Industrial
Technologies. Energy Efficiency and Renewable Energy. June 2001.