In any power plant our aim is to have 100% availability of the plant but practically it is not possible since all equipment needs periodical maintenance.
Improvement in Plant availability
In any power plant our aim is to have 100% availability of the plant but practically it is not possible since all equipment needs periodical maintenance which is to be planned properly which is known as a planned maintenance. Sometimes equipment fails/trips due to some unplanned reason and causes plant outage. This outage is called a forced outage.
The planned outage is taken as per the recommendation of OEM (Original equipment manufacturer) to carry out maintenance to achieve reliable operation of the unit.
This planned outage period is decided so we know the reduction in % availability of the unit.
A forced outage is due to failure of some equipment or tripping of some equipment on protection. This is a matter of concern since it affects the availability of the unit and in turn reduction in power generation and hence plant load factor and increased oil consumption due to re-startup and thereby the increased cost of generation.
Forced outage:
Boiler tube leakage is the major reason for the forced outage in a coal-fired power plant.
Boiler tube leakage occurs due to following reasons:
Fireside erosion
Waterside corrosion
Overstressing
Starvation
Overheating of tubes
Creep life exhaustion
Hydrogen embrittlement
Thermal shocks
Improper operation practices
Poor maintenance
Welding defects
Erosion by ash and erosion by secondary air leakages are a significant cause of boiler tube failure.

Author's Bio: 

Marcep Inc. is a division of Marcep Group which has a JV with some of the major projects over the world and has entered the Asian market in sharing knowledge to the industry.