Boiler Shutdown Maintenance

July 08, 2020

Boilers are critical components in many factories, providing the steam necessary for various industrial processes. However, there may be special reasons requiring boilers to be shut down temporarily. During these periods, boilers are susceptible to oxidative corrosion if left unused, leading to efficiency losses and increased operational costs. This guide outlines proven methods to protect your boiler from oxidative corrosion during shutdown periods, ensuring their longevity and reliability.

Boiler maintenance

Effective Maintenance Strategies for Boiler Shutdowns

1:Drying the Boiler (Short-term Maintenance)

After the boiler operation ceases, it's imperative to reduce the water temperature inside the boiler to 100°C. Following this, drain the furnace water and utilize the residual heat or introduce hot air to dry the interior. This method is most suitable for short-term maintenance, preventing internal moisture that could lead to corrosion.

2:Nitrogen Filling (Long-term Maintenance)

For long-term shutdowns, after draining and drying as described above, fill the boiler with nitrogen at 99% purity, maintaining a pressure of 0.05Mpa. This inert atmosphere prevents oxidative reactions, making it an ideal strategy for preserving the boiler's integrity over extended periods.

3:Oxygen Removal Strategies

To prevent oxygen in the water from reacting with the boiler metal, consider the following approach for short-term shutdowns (within 10 days):

Seal the boiler tightly by closing all valves and baffles after shutdown.

Slow down the cooling process to minimize temperature gradients that could encourage corrosion.

Maintain steam pressure above atmospheric levels and water temperature above 100°C, which helps in preventing corrosion by keeping oxygen out of contact with the boiler metal.

For long-term shutdowns, it's crucial to cool the boiler completely and adopt a different strategy:

4:Preventing Metal Reaction with Oxygen

Filling the boiler with alkali water provides a protective layer against oxidation:

Clean the boiler interior to remove scale, rust, and other contaminants.

Inspect and close all related valves tightly to ensure the boiler forms a closed container.

Gently heat the boiler to 80-100°C, ensuring the solution is uniformly heated for even distribution.

Add 10kg of NaOH or 20Kg of KH2PO4 per ton of water, monitoring the pH level every 5 days to maintain it between 10-12. This alkaline environment prevents oxidative reactions between water and the boiler metal.

Maintenance Schedules and Safety Precautions

Regular maintenance schedules and safety precautions are paramount. Always wear appropriate personal protective equipment (PPE) when handling chemicals or performing maintenance tasks. Consult with professionals for complex maintenance activities or when specific conditions require expert assessment.

Conclusion

Proper boiler shutdown maintenance is crucial for extending the life and efficiency of boilers. By implementing the strategies outlined in this guide, you can protect your boilers from oxidative corrosion during shutdown periods. Regular checks and professional assessments ensure safety and operational readiness, saving costs and preventing unexpected breakdowns in the long run.