Why Boiler maintenance or repair is required?
Boilers are the heart of many industries—power generation plants, chemical processing, sugar mills, textile industries, and refineries all rely on them for consistent steam supply. Because of the elevated operating pressures and temperatures, the risks are also greater. Proper maintenance of high-pressure boilers is not just about ensuring efficiency—it is essential for safety, compliance, and extending the lifespan of this critical equipment.
boilers face extreme stress due to continuous exposure to high temperature and high-pressure steam. Without systematic maintenance, they are vulnerable to failures that can lead to;
- Boiler explosions
- Reduced efficiency
- Unplanned shutdown
- More fuel consumption
What are the major problems in high pressure Boilers which call for periodic maintenance or repair of the Boilers??
Major problems in high pressure Boilers;
1-Boiler tubes/pressure parts failure.
2-Tubes internal scaling and corrosion
3-Tubes external scaling and corrosion
4-Feed pumps failure
5-Boiler fuel feeding system failure
6-Fuel handling failure
7-Air compressors failure
8-Boiler fans (ID, FD, PA or SA fans) failure
9-Soot blower issues
10-High pressure valves leakage/passing
11-Issues in grates or bed or bubble caps
12-Flue gas and air leakages
13-Electrical system failure
14-Motors breakdown
15-Failure in instrumentation system
16-Instrumentation malfunction
17-Power supply failure
What are the different types of maintenance activities carried out in Boilers?
Preventive, Proactive and Breakdown maintenance are generally used to carryout in Boilers.
What are the inspection and maintenance activities used to carryout during Boiler Annual shutdown?
After shut down, boiler is allowed to cool naturally ensuring desired water level in the Boiler, after cooling following are the Maintenance or services carried out.
1-Ash cleaning: Ash accumulated at various zones like furnace, super heaters, economiser, APH will be cleaned thoroughly.
2-Boiler pressure parts cleaning: The soot & scale formed on all pressure parts like water wall tubes, economiser coils are cleaned through manual scraping or high-pressure water jet cleaning.
3-Pressure parts inspection and thickness mapping: All cleaned pressure parts should be inspected thoroughly for any abnormality like crack, bend, dent marks, pitting, skin burn etc.
Thickness of all pressure parts should be thoroughly checked with the help of Ultra sonic thickness machine. And ensuring no reduction of tubes thickness more than 5 to 10% than original thickness.
4-Valves servicing/overhauling: Boiler and auxiliary steam lines valves thoroughly inspecting and servicing as per requirement.
Valves servicing procedure:
- Clean the valve.
- Dismantle the valve.
- Clean the valve internals like seat, disc, stem, spring etc.
- Conduct seat lapping and blue match.
- Replace the consumable items like seal ring, gland packings, gaskets, damaged/worn out nut bolts etc.
- Check the run out of stem
- Assemble the valve
4-Boiler inspection: After cleaning, inspection and servicing of valves Boiler open inspection and Hydraulic tests are carried out by internally and externally in presence of Boiler Inspector.
If both the tests are satisfactory then, Boiler can be boxed up or else rectification should be done.
Procedure for Boiler tubes repair or replacement.
- Identify the tubes or any other pressure part to be removed. Tubes must be removed carefully to prevent harm to adjacent tubes and tube sheets.
- Cut the defective tube ends using tube cutters, gas cutting, or grinding.
- Measure and cut replacement tubes of the same material grade, diameter, and thickness (as per design/IBR).
- Bevel the tube ends as per required joint (welded or expanded type).
- Weld set up the new tube
- Position correctly with required projection length.
- For welded connections, tack weld first, then carry out full welding as per WPS (Welding Procedure Specification).
- Carryout Preheat and post-weld heat treatment (PWHT) if material demands it.
- Grind and smoothen weld joints.
- Carry out NDT on welded joints (RT/UT if applicable).
- Conduct hydraulic test as per IBR norms (usually 1.5 times working pressure).
- Check for leaks and rectify if found.
Other Non-Pressure parts maintenance activities are
4-Air Pre-Heater Tubes cleaning: Air heater tubes cleaning generally involves brushing of tubes internal area. In some APH tubes air passes through the tubes and flue gas from out side the tubes, in such APH external cleaning of Tubes is carried out.
5-Fuel feeding system maintenance: Clean all the fuel feeding system thoroughly, inspect for leakages, damages. Check the thickness of ducts and fuel carrying lines.
Carryout the servicing of all rotary parts like Drag chain feeders, coal spreaders, screw feeders, drum extractors etc.
Insect thoroughly the screw splines and replace the screw if flights thickness found reduced due to erosion.
6-Servicing of Boiler feed pumps.
Boiler feed pumps are critical for supplying high-pressure water to the boiler. Their efficient operation ensures safe boiler performance. Regular servicing prevents breakdowns, leakage, and efficiency losses.
7-Servicing of Boiler fans:
Boiler fans like ID, FD, PA and SA fans regular preventive maintenance is vital part of maintenance activities.
Following are the general and regular activities for Fans maintenance.
- Cleaning of the fan
- Thorough inspection of impeller and vanes
- Ensuring no erosion, corrosion and damages to the fan parts
- Hard facing of worn out area (For ID fans only)
- Impeller and inlet cone gap checking
- Hub not bolts tightness checking
- Fan casing inspection for damage
- Both Drive and Non-drive end bearing inspection and replacement if required
- Coupling inspection
- Motor overhauling
- Realignment and trial
8-Soot blowers servicing
10-All Motorized valves (MOVs) and control valve servicing, setting and calibration
11-Boiler Thermal expansion pointers cleaning and refitting
12-Air, flue gas ducts and expansion bellows cleaning and inspection
13-Travelling grate overhauling in case of Travelling grate Boilers
14-Bed blade, fuel nozzles and air nozzles cleaning, inspection and replacement if required in case of AFBC boilers
15-Refractory inspection and repair
16-Insulation inspection and repair.
What are the break downs or unplanned maintenance activities do you expect in Boilers?
Major Break downs or unplanned maintenance activities in Boilers are;
1-Boiler tubes leakage, burst or weld joint leakage
2-Flue gas or air leakage
3-Air Preheater (APH) chocking
4-Boiler fans break down due to Mechanical, electrical or instrumentation part failure
5-Steam or water line gaskets failure
6-Boiler feed pumps failure
How do you bring back Boiler into service after Boiler tube failure?
Following are the step by step activities to be carried out after tube leakage
- After identifying the tube leakage, stop the Boiler
- Inform the Boiler inspector
- Carryout fast cooling by keeping ON ID & FD fans
- Ensure continuous circulation of feed water
- Simultaneously start to depressurise the Boiler
- After cooling down, stop the fans and Pumps
- Obtain work permit and isolate all the electrical, pneumatic and hydraulic power by applying LOTO and Tag.
- Drain the water as per your requirement i.e below the level where tube leakage has observed
- Clean the leakage tube
- If leakage is minor, it can be arrested by grinding and welding
- If leakage is more and calls for tube replacement then follow the below procedure.
- Cut the defective tube ends using tube cutters, gas cutting, or grinding. Measure and cut replacement tubes of the same material grade, diameter, and thickness (as per design/IBR).
- Bevel the tube ends as per required joint (welded or expanded type).
- Weld set up the new tube
- Position correctly with required projection length.
- For welded connections, tack weld first, then carry out full welding as per WPS (Welding Procedure Specification).
- Carryout Preheat and post-weld heat treatment (PWHT) if material demands it.
- Grind and smoothen weld joints.
- Carry out NDT on welded joints (RT/UT if applicable).
- Conduct hydraulic test as per IBR norms (usually 1.5 times working pressure).
- Check for leaks and rectify if found.
What are the proactive or condition monitoring system carried out in Boilers maintenance and services?
Following are the major proactive or condition monitoring system carried out in Boilers maintenance and services.
1-Boiler pressure parts/tubes thickness checking at every half yearly or yearly.
2-Boiler all critical valves like safety valves, main steam stop valve and feed control station valves servicing through OEM (Original Equipment Manufacturer)
3-Tubes leak mapping
4-Tubes wear rate monitoring
5-Tubes corrosion and scaling monitoring
6-Other Non-destructive tests through Boiler Remaining Life assessment test (RLA test)
7-Boiler feed pumps routine preventive maintenance and major servicing through OEM
8-Boiler fans routine preventive maintenance and major servicing yearly
9-Soot blowers’ routine maintenance 10-Thermal expansion pointers inspection & monitoring expansion at different operating conditions
