Boiler Feed Water Parameter Limits as per Indian Boiler Regulations (IBR)
Boiler feed water quality is one of the most critical factors in ensuring safe, efficient, and long-lasting boiler operation. The Indian Boiler Regulations (IBR) specify strict limits for feed water parameters to prevent scaling, corrosion, foaming, and carryover. These limits vary depending on whether the boiler is low-pressure, medium-pressure, or high-pressure, since operating conditions and risks differ.
In this blog, we’ll explore the IBR feed water parameter limits and provide detailed explanations of why each parameter is important.
🔍 Boiler Feed Water Parameter Limits
⚙️ Detailed Explanation of Each Parameter
1. Hardness (as CaCO₃) – 5 PPM max
- Low Pressure Boilers: Small amounts of hardness may be tolerated, but scaling reduces efficiency.
- Medium Pressure Boilers: Scaling risk increases with temperature; hardness must be minimized.
- High Pressure Boilers: Even trace hardness can cause severe deposits and tube failures.
- Justification: Hardness salts (calcium and magnesium) form scale on boiler tubes, reducing heat transfer and increasing fuel consumption. Hence, hardness must be kept below 5 PPM.
2. pH – 8.5 to 9.5
- Low Pressure Boilers: Slightly alkaline water prevents acidic corrosion.
- Medium Pressure Boilers: Maintaining pH ensures balanced alkalinity without causing caustic embrittlement.
- High Pressure Boilers: Strict pH control is vital to prevent both acidic corrosion and caustic attack.
- Justification: pH in the range of 8.5–9.5 ensures water remains alkaline, protecting boiler metal surfaces while avoiding excessive alkalinity that can damage equipment.
3. Dissolved Oxygen (O₂) – Nil
- Low Pressure Boilers: Oxygen causes pitting corrosion in boiler tubes.
- Medium Pressure Boilers: Oxygen removal is critical to prevent rapid corrosion at higher temperatures.
- High Pressure Boilers: Absolutely essential to eliminate oxygen, as even trace amounts can cause severe damage.
- Justification: Dissolved oxygen is highly corrosive. Oxygen scavengers (like sodium sulphite or hydrazine) and deaerators are used to ensure oxygen-free feed water.
4. Oil – Nil
- Low Pressure Boilers: Oil contamination can cause foaming and deposits.
- Medium Pressure Boilers: Oil films reduce heat transfer and cause localized overheating.
- High Pressure Boilers: Oil contamination is unacceptable, as it leads to turbine fouling and serious damage.
- Justification: Oil in feed water interferes with heat transfer, causes foaming, and contaminates steam. Therefore, oil must be completely avoided.
5. Total Dissolved Solids (TDS) – Minimum less than 100 ppm if possible to reduce blowdown
- Low Pressure Boilers: Higher tolerance, but excessive TDS causes foaming and carryover.
- Medium Pressure Boilers: TDS must be controlled to prevent scaling and steam contamination.
- High Pressure Boilers: Very strict control required; high TDS leads to turbine deposits and efficiency loss.
- Justification: TDS represents dissolved salts in water. High TDS increases blowdown frequency, wasting energy and water. Keeping TDS at the minimum possible level reduces blowdown and improves efficiency.
📊 Summary Table: Parameter Justification Across Boiler Pressures
📌 Conclusion
Maintaining boiler feed water quality within IBR limits is essential for safe and efficient operation.
- Low-pressure boilers allow slightly more tolerance but still require strict hardness and oxygen control.
- Medium-pressure boilers demand balanced chemical treatment to prevent scaling and corrosion.
- High-pressure boilers require the most stringent control, as even trace impurities can cause severe damage to steam turbines and boiler tubes.
By adhering to these limits, industries can achieve higher efficiency, reduced maintenance costs, and longer equipment life.
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