Boiler Water Quality Parameters as per IBR for Low, Medium, and High Pressure Boilers
Maintaining proper boiler water chemistry is essential for safe operation, efficiency, and compliance with the Indian Boiler Regulations (IBR). The IBR specifies strict limits for 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 boiler water parameter limits and provide justification for each parameter across different pressure ranges.
🔍 Boiler Water Parameter Limits (IBR)
⚙️ Parameter Justification for Different Boiler Pressures
1. Hardness (as CaCO₃) – Not Detectable
- Low Pressure Boilers: Even small hardness levels cause scaling, reducing efficiency.
- Medium Pressure Boilers: Scaling risk is higher due to elevated temperatures.
- High Pressure Boilers: Absolutely critical to eliminate hardness, as even trace amounts can cause severe deposits and tube failures.
2. Sodium Sulphite (Na₂SO₃) – 30–70 PPM
- Low Pressure: Acts as an oxygen scavenger, preventing corrosion.
- Medium Pressure: Required in controlled amounts to balance oxygen removal without excess chemical carryover.
- High Pressure: Usage is limited; excess sulphite can decompose at high temperatures, so hydrazine is preferred.
3. Sodium Phosphate (Na₃PO₄) – 50–100 PPM
- Low Pressure: Helps precipitate hardness salts and maintain alkalinity.
- Medium Pressure: Controls scaling and stabilizes pH.
- High Pressure: Must be carefully dosed; excess phosphate can lead to carryover and deposits in turbines.
4. Caustic Alkalinity (as CaCO₃) – ≥ 350 PPM
- Low Pressure: Ensures water remains alkaline, preventing acidic corrosion.
- Medium Pressure: Higher alkalinity is needed to protect against acid attack.
- High Pressure: Controlled alkalinity is vital; excessive levels can cause caustic embrittlement of boiler metal.
5. Hydrazine (N₂H₄) – 0.1–1.0 PPM
- Low Pressure: Provides oxygen scavenging, though sulphite is more common.
- Medium Pressure: Effective in reducing oxygen without adding dissolved solids.
- High Pressure: Preferred scavenger, as it decomposes into harmless nitrogen and water, avoiding contamination.
6. Total Alkalinity (as CaCO₃) – ≤ 1200 PPM
- Low Pressure: Higher tolerance, but excessive alkalinity can cause foaming.
- Medium Pressure: Must be controlled to prevent carryover.
- High Pressure: Strict limits are essential to avoid steam contamination and turbine deposits.
7. Suspended Solids (TSS) – ≤ 50 PPM
- Low Pressure: Solids can settle and cause scaling.
- Medium Pressure: Deposits reduce heat transfer efficiency.
- High Pressure: Even small amounts can cause serious damage; strict control is mandatory.
8. Dissolved Solids (TDS) – ≤ 3500 PPM
- Low Pressure: Higher tolerance, but blowdown is needed to control foaming.
- Medium Pressure: Must be reduced to prevent carryover.
- High Pressure: Very strict control required; high TDS leads to steam contamination and turbine fouling.
9. Silica (SiO₂) – < 0.4 of Caustic Alkalinity
- Low Pressure: Less critical, but still monitored.
- Medium Pressure: Can volatilize and deposit on steam equipment.
- High Pressure: Extremely important; silica carryover causes turbine blade deposits, reducing efficiency and risking damage.
📌 Conclusion
IBR boiler water parameter limits are designed to ensure safe and efficient operation across all pressure ranges.
- Low-pressure boilers have more tolerance but still require strict hardness and alkalinity 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 maintaining these parameters within IBR limits, industries can achieve higher efficiency, longer equipment life, and compliance with safety standards.
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