Failure investigation of super heater tubes of coal fired power plant

Running head: RISK MANAGEMENT
[Risk Management]
[Name of the Student]
[Name of the University]
[Author note]

2RISK MANAGEMENT
Failure investigation of super heater tubes of coal fired power
plant
[Name of the Student] [Student ID]
1. Introduction
The report mainly discusses about the analysis of the failure that occurred in two adjacent super heater
tubes that were made up of CrMo steel. This was a 60 MW thermal power plant that made use of the
coal. The major reason lying behind the failure was due to the oxide deposition upon the internal
surface of the tube and this deposition was initially responsible for the creation of a significant
amount of resistance for the heat transfer process [1]. This in turn was associated with undesirable rise
in the temperature of the components. Besides this the report has also been associated with proposing
the risk mitigation strategy as well.
2. Research and Theory on the Problem
2.1. Specific Theory – In a power plant the prime importance is provided to the process required for
the purpose of generating electricity without the existence of any kind of forced outages. The major
concern for the forced outages in the coal fire station is due to eh failure of the super heater tube of the
boilers. The major reason lying behind the damage occurring over the time of operation is due to the
flowing of the fuel gases over the super heater tubes. This type of damage is often termed as the
fireside damage or corrosion. This type of damage is generally dependent upon the coal quality, as
well as on the materials that are being used along with the various operations and the maintenance. It
is seen that the tubes interior is generally vulnerable and are primarily dependent upon the water
quality that is used for the generating steam of high pressure [2]. So there is an essential need of a
steady or continuous flow of steam so as to make sure that the materials of the tube are maintained
under the temperature that has been prescribed. In case of its absence there exists the high possibility
of shooting-up of the temperature which in turn is responsible for the detrition of the materials as well
as the subsequent failure at a fast rate. For such instances the overall efficiency of the plant is entirely
dropped. So it is very essential to analyse the failure of the tubes in order to find as solution for taking
certain actions that would be helping in avoiding such kind of risks in the future [3].
2.2. Specific Theory – Risk and Management
The possible ways that are to be adopted in order to eliminate the further risks similar to the boiler
incident have been listed below:

3RISK MANAGEMENT
 The tube wall are to be cleaned at regular intervals in order to avoid similar incidents. The regular
checking would be helping a lot in detecting any kind of defects if occurs before any kind of
severe consequences. This would be helping a lot in removing all the hindrance or the
heterogeneities as well [4].
 One major thing that is to be done is checking the quality of water. This is to be done at regular
intervals. The major reason behind doing this is for the purpose of making sure that all the pH and
the oxygen level is maintained at specified levels.
 Another problem which might occur is due to the contamination of the water. This mainly occurs
due to the leakage in the tubes that might lead to high salt concentration in the water. By regular
monitoring it is possible to eliminate this kind of risk as well.
 The strength of the materials are to be checked as well so as to eliminate the risk of the thickening
of boundary walls [5].
 Maintenance of the oxide scale so as to make sure that there is smooth heat transfer that would be
helping in the elimination of risks related to overheating of the tube walls.
 All this things are to be maintained in order to eliminate the risks related to bulging which mainly
occurs due to high hoop stress that might be leading to failure.
3. Link between Case Evidence and Theory
The damage of the tubes were visible with naked eyes only. It was observed that both of the tubes
were associated with experiencing a temperature of around 540 C and was associated with a stress
level of around 100kg/cm2 at the time of operation. In one of the sample it was observed that there
existed fish mouth cracking I one side whereas on the other side of the welding there was a bulge.
Besides this there also existed a layer wise corrosion at the open end of the crack [6]. Besides this
there existed a drastic decrease in the thickness of the walls as well. There also existed multiple cracks
in the inner surface in the longitudinal direction but this type of cracks were entirely absent in the
outer surface. So it was observed that the outer surface was blackened that lead to thermal effect
whereas the inner surface was entirely deep brown in colour having multiple red spots.
Some of the facts that were identified after analysing the entire incident have been listed below:
 Cr-Mo low alloy steel was used for the purpose of making the component and besides this the
composition was very much close to the specification of the polish. Some of the specifications
mainly includes the DIN 10CrMo910/T22. Besides this it was also observed that the major
chemical concentrations were within the limit that was specified previously.
 It was seen that there existed polygonal fertile grains as well as alloy carbide in the
iMicrostructure of the steel tube. At the time of service exposure there occurred the formation of
oxide scales in the interior of the tube. During the time when it was observed that the thickness
become substantial then it was time when the process of heat transfer was hindered all across the