Understanding Steam Boiler
MAINTENANCE & INSPECTION
BOILER MAINTENANCE
Maintenance is derived from the word "maintain" which has the following meanings carry on, preserve, support, sustain, keep up and keep supplied.
What is maintenance ?
Work or activities done to ensure the plant/equipment is safe and efficient to operate at its design capacity.
Types of maintenance
- Corrective maintenance
- Preventive maintenance
- Predictive maintenance
For boiler system, it means :-
- Ensure safe operation by regular inspection
- Keep the boiler in operation
- Keep the boiler in operating condition
- Restore boiler efficiency
- Repair the damaged parts and keep it tight
- To clean the boiler
Maintenance Objectives:-
From the definition, boiler maintenance is any work done on the boiler system so as to meet certain objectives.
These objectives are :-
- Keep the boiler in operation so as to meet the design load
- Maintain full reliability and maximize availability by zero unplanned down time and optimize planned down time
- Meet safety and regulatory requirements
Activities
- Routine service (preventive)
- Repair (corrective)
- Inspection (preventive/predictive)
- Overhaul (predictive)
Types of Maintenance (Generic)
Type Rate Requirement
1. Routine
Daily, Weekly, Monthly or
Yearly (incl. regulatory
inspection)
Require Procedure and
Instruction including record
keeping
2. Predictive
depend on plant
maintenance philosophy and
program
Requires special tool or program
i.e. RBI, CBM
3. Preventive depending on O & M
requirements
Regular inspection and test
during operation or shutdown
4. Reactive
(Corrective)
when boiler system fail and
damage
May require stock of part and
external expertise
Boiler Cleaning
• Tube cleaning is used to remove waterside deposits to prevent tube failure. Two methods are available
– Mechanical cleaning
– Chemical cleaning
• Mechanical cleaners consist of a rotating cutter head driven by an air-powered motor that fits inside the tube.
• Chemical cleaning solution is a 5% hydrochloric acid solution with an inhibitor added to lessen boiler metal acid attack. Two cleaning methods are available
– Circulation
– Static (Fill and Soak)
Burner cleaning - cleaning of burner tips from blockage which can affect combustion. Precaution has to be taken during cleaning so as not to damage the tips. Worn out or damaged tips can result in improper combustion
Soot blowing - cleaning of boiler tubes from deposits of unburned fuel elements (soot) while the boiler is in operation. Cleaning media could be steam, air or use of a vibrator. Dirty boiler tubes can result in poor heat transfer in the boiler and hence reduce efficiency.
Strainer cleaning - cleaning of fuel strainers from blockage. Dirty strainers can easily be noticed by the increase in the differential pressure across the strainers
Flame scanner/photo-cell cleaning - cleaning of flame sensing equipment from dirt, soot or any other substance which can reduce the tendency of detecting the flame. Dirty flame sensing equipment can result in boiler tripping.
Testing of boiler water - taking of boiler water samples and tested for alkalinity and contaminants. Contaminated water can lead to tubes blockage, over firing and reduction in output/efficiency.
Where as improper alkalinity can lead to problems of corrosion Draining of condensate - removing of water in steam pipelines. Presence of water in pipelines can lead to water hammer. Steam together with the slug of water travel at a very high velocity hit
any obstruction downstream and can result in severe damage.
Testing/cleaning of water gauge - blowing of steam and water through the steam and water passage of the gauge glass so as to clear any blockage which can cause false level indication.
Testing of control systems - important control devices such as low water fuel cut-out, combustion system, safety valves are to be tested for their accurate operation so as to ensure that they respond as designed.