Routine Checking of Boiler During Normal Operation: Safety, Efficiency, and Best Practices

Routine Checking of Boiler During Normal Operation: Safety, Efficiency, and Best Practices

Boilers are the backbone of power plants, industrial facilities, and manufacturing units, generating steam for energy and process applications. Since boilers operate under high pressure and temperature, routine checking during normal operation is essential to ensure safety, efficiency, and reliability.  

Regular monitoring helps detect abnormalities early, prevents accidents, and maintains optimum performance.  

🔹 Key Checks During Normal Boiler Operation

1. Fuel and Ash Handling Systems

- Ensure sufficient fuel availability.  

- Verify that fuel handling equipment is healthy and free from faults.  

- Confirm that the ash handling system is working properly without jamming or blockages.  

2. Field Equipment Performance

- Inspect smooth operation of:  

  - Induced Draft (ID) Fan  

  - Forced Draft (FD) Fan  

  - Boiler Feed Pump  

  - Electrostatic Precipitator (ESP)  

  - Bag Filter  

  - Dosing Pumps  

  - Pulverisers and Feeders  

  - Instrument Air Compressor  

3. Water Level and Leakage

- Water level at the gauge glass must be within the normal range and match remote readings.  

- Check for leakages in steam, feedwater, flue gas, and fuel systems.  

4. Chemical Dosing and Cooling

- Ensure sufficient dosing chemicals are available in the dosing tank.  

- Confirm cooling water supply to all coolers.  

5. Instrument Readings and Valves

- Field instrument readings must match remote readings.  

- Verify the position of control and isolation valves as per operational requirements.  

🔹 Handling Abnormalities

- Any abnormality should be rectified promptly when conditions permit.  

- Maintain a defect register to record issues for future rectification.  

- Audible and visual alarms at the control panel alert operators to abnormalities. Immediate corrective action is required to restore normal operation.  

🔹 Soot Blowing

- Soot deposits on boiler tubes reduce heat transfer efficiency and increase exhaust flue gas temperature.  

- Soot blowing must be carried out whenever required.  

- Frequency depends on the type of fuel used in the boiler.  

🔹 Logging and Monitoring

- Maintain a log book to record important parameters.  

- Modern DCS (Distributed Control System) and PLC (Programmable Logic Controller) systems provide trending facilities for effective monitoring.  

- Manual logging at intervals of 1–2 hours is also recommended.  

Parameters to Log

- Rate of fuel feeding  

- Steam generation (flow)  

- Final superheater steam temperature  

- Final steam pressure  

- Air supply and air temperature  

- Draft at various zones  

- Flue gas temperature at different zones  

- Feedwater inlet temperature  

- Drum level  

- Current taken by various drives  

- Ash hopper level  

- Coal feeder speed  

- Grate speed  

- Bed temperature  

- Pressure drop across fuel bed  

Additional parameters may be added based on operational requirements.  

📌 Key Takeaways

- Routine checks ensure safe and efficient boiler operation.  

- Monitoring fuel, ash, water levels, and equipment performance is critical.  

- Logging parameters helps in trend analysis and preventive maintenance.  

- Soot blowing and defect registers improve reliability and reduce downtime.  

Wet and Dry Preservation of Boilers: Methods, Importance, and Best Practices

Wet and Dry Preservation of Boilers: Methods, Importance, and Best Practices

Boilers are critical equipment in power plants, refineries, and industrial facilities, designed to generate high‑pressure steam at elevated temperatures. When a boiler is taken out of service for a longer period, special care must be taken to prevent corrosion of pressure parts. Boiler tubes corrode rapidly in the presence of oxygen and moisture, so preservation methods are essential to ensure safety, reliability, and long service life.  

There are two primary methods of boiler preservation: Dry Preservation and Wet Preservation.  

🔹 Why Boiler Preservation is Necessary

- Prevents corrosion and pitting in boiler tubes and pressure parts.  

- Ensures long‑term reliability when boilers are idle.  

- Reduces maintenance costs and downtime.  

- Extends the lifespan of economisers, superheaters, and steam drums.  

🔹 Dry Preservation of Boilers

Definition

Dry preservation involves keeping the boiler tubes moisture‑free during shutdown.  

Process

- The boiler is completely drained of water.  

- Dry air is circulated continuously through the empty boiler tubes.  

- Moisture is eliminated to prevent corrosion.  

Advantages

- Effective for short‑term shutdowns.  

- Prevents moisture‑induced corrosion.  

Limitations

- Difficult to maintain in modern boilers with complex designs and multiple bends.  

- Not always practical for long‑term preservation.  

🔹 Wet Preservation of Boilers

Definition

Wet preservation eliminates oxygen from the boiler tubes by filling them with treated water.  

Process

- Boiler pressure parts (economiser, steam drum, water wall, and superheater) are filled with feedwater containing high concentration of hydrazine (200 ppm).  

- Hydrazine ensures no dissolved oxygen remains in the feedwater.  

- The boiler is kept under pressure so that atmospheric air cannot enter the pressure parts.  

Advantages

- More effective and easier than dry preservation.  

- Suitable for long‑term shutdowns.  

- Prevents both oxygen corrosion and moisture damage.  

Limitations

- Requires chemical treatment (hydrazine or equivalent oxygen scavenger).  

- Needs careful monitoring of water chemistry.  

🔹 Wet vs Dry Preservation: Comparison

📌 Key Takeaways

- Dry Preservation keeps boiler tubes moisture‑free using dry air circulation.  

- Wet Preservation eliminates oxygen using hydrazine‑treated feedwater under pressure.  

- Wet preservation is preferred in modern boilers due to complex tube designs.  

- Proper preservation ensures safety, efficiency, and extended boiler life.  

Common Welding Defects: Causes, Prevention, and Best Practices

🔧 Common Welding Defects: Causes, Prevention, and Best Practices

Welding is a critical process in industries such as construction, automotive, aerospace, and manufacturing. While it ensures strong joints and durability, welding defects can compromise the integrity of structures, leading to costly repairs or even catastrophic failures. Understanding the types of welding defects, their causes, and prevention methods is essential for welders, engineers, and quality inspectors.

This Blog covers the most common welding defects including cracks, porosity, undercut, overlap, spatter, underfill, distortion, slag inclusion, incomplete fusion, and incomplete penetration.

⚡ Crack

Cracks are considered the most dangerous welding defect because they can rapidly propagate, leading to structural failure.

Types of Cracks

• Longitudinal cracks → Form parallel to the weld bead.
• Transverse cracks → Form across the width of the weld.
• Crater cracks → Appear at the end of the bead where the arc stops.
• Hot cracks → Occur at high temperatures (above 1000°C) due to incorrect filler metal or rapid heating/cooling.
• Cold cracks → Form after cooling, sometimes hours or days later.

Causes

• Use of hydrogen shielding gas in ferrous metals.
• Residual stress in ductile base metals.
• Rigid joints restricting expansion/contraction.
• High levels of sulphur and carbon.

Prevention

• Preheating metals and gradual cooling.
• Maintaining proper weld joint gaps.
• Selecting correct filler and base materials.

🌬️ Porosity

Porosity refers to holes in the weld bead caused by trapped gas bubbles, reducing weld strength.

Causes

• Unclean welding surface.
• Wrong electrode selection.
• Lack or excess shielding gas.
• Damaged shielding gas cylinder.
• Incorrect welding current or fast travel speed.

Prevention

• Clean weld surfaces thoroughly.
• Use correct electrodes.
• Preheat metals before welding.
• Adjust shielding gas flow rate.
• Regularly check shielding gas cylinders for moisture.
• Optimize current and travel speed.

🪓 Undercut

An undercut is a groove along the weld toe caused by excessive current or insufficient filler metal.

Causes

• High arc voltage.
• Wrong electrode angle.
• Excessive travel speed.

Prevention

• Reduce arc length, voltage, and travel speed.
• Maintain a 30–45° electrode angle.
• Use smaller electrode diameters.

🔄 Overlap

Overlap occurs when excess filler metal spreads around the bead without fusing properly with the base metal.

Causes

• Incorrect welding procedure.
• Wrong material selection.
• Poor base metal preparation.

Prevention

• Use smaller welding current.
• Apply proper welding techniques.
• Shorter electrode length.

✨ Spatter

Spatter is the discharge of molten droplets that stick to the surface, increasing cleanup costs.

Causes

• High arc length or current.
• Poor shielding of the heat‑affected zone.
• Wrong polarity.

Prevention

• Correct polarity selection.
• Better shielding gas and technique.
• Reduce current and arc length.

📉 Underfill

Underfill occurs when insufficient weld metal is deposited, leaving unfused parent material.

Causes

• Low current.
• High travel speed.
• Incorrect bead placement.
• Thin weld beads in multi‑pass welding.

Prevention

• Select proper electrode size.
• Use correct current settings.
• Avoid excessive travel speed.

🔥 Distortion

Distortion or warping is an unintended change in shape due to excessive heating.

Causes

• Thin weld metal.
• Incompatible base and filler metals.
• Too many weld passes.

Prevention

• Use suitable weld metals.
• Optimize number of passes.
• Select appropriate welding methods.

🪨 Slag Inclusion

Slag trapped in the weld bead reduces toughness and strength.

Causes

• Incorrect torch angle and travel speed.
• Poor cleaning of weld edges.
• Low current density.

Prevention

• Use higher current density.
• Maintain optimal torch angle and speed.
• Clean weld edges and remove slag between passes.

🔗 Incomplete Fusion

Occurs when base and filler metals fail to fuse, leaving gaps.

Causes

• Low heat input.
• Wrong joint or torch angle.
• Oversized weld pool.

Prevention

• Increase current and reduce travel speed.
• Improve welding positions.
• Lower deposition rate.

📏 Incomplete Penetration

Incomplete penetration happens when the root of the joint is not fully fused, common in butt welds.

Causes

• Incorrect welding technique.
• Wrong electrode size.
• Low deposition rate.

Prevention

• Use proper welding procedures.
• Increase deposition rate.
• Select correct electrode size.

✅ Conclusion

Welding defects such as cracks, porosity, undercut, overlap, spatter, underfill, distortion, slag inclusion, incomplete fusion, and incomplete penetration can significantly reduce the strength and reliability of welded joints. By understanding their causes and prevention methods, welders can improve quality, reduce rework, and ensure safety in critical applications.