Boiler Tube Research (Riser) Part 3 Final.

Please visit Boiler Tube Research (Riser) Part 2 for previous explanation.

Of the analysis result of a photograph micro structure and the violence in the area around the crack:

1. Micro structure on metal parent good to the pipe and plate is ferrite and pearlite. There is no significant differences between them .While on metal welding and haz there was no evidence that the phase martensite brittle.

2. Difficult determine whether cracks in the form of intergranular or transgranular.
3. The photos of SEM look happened propagation crack where at the end of around cracks were many micro crack indicated a dynamic burden to climbing cracks.

4. Of the analysis result of EDX did not find any elements that causes corrosion as the cause of propagation crack as ions cl and s. And from a crack that there were also not characterizing the existence of the involvement of the process of corrosion on crack.

5. From the results of the violence it is evident that weld metal having value violence highest and metal parent to the pipe having value at the lowest violence where propagation crack happened



Mechanical analysis and thermal is hypothesized that appeared after analyzing the results of a visual inspection and micrography a pipe 5 is that a crack that happened to the pipe 5 most likely caused by the cyclic loading good thermal mechanical and.

Cyclic a mechanical loading to the pipe 5 occurred because the pipe near the bottom of a boiler. As a result vibration to the pipe may be due to the process of combustion that goes. Cyclic loading in thermal occurred because the possibility of not inconsistency in combustion temperature inside of a boiler in various points.

Hopefully with a the force of gravity enables bottom ash tending to move down and hit a pipe 5 with the variations of temperature different .Lacing bottom ash this is happening in a recurrent manner to the pipe 5. The phenomenon of this is that likely produces vibratory to the pipe , and in end up creating voltage concentration .

In addition to the external factor , profile of weld which is found in pipe connections 5 and plate was likely produce the concentration of high voltage in the area were. For that , the simulation was done to prove whether there is the concentration of high voltage over a given area in weld connection.

Simulation for pipe 5 aims to prove that hypothesis that crack that occurs more is because of the concentration of voltage on weld regions. Voltage this appears a consequence of the burden of thermal (inside and outside of the pipe) and fluid pressure from in a pipe.

Geometry for modeling and types of materials used for the purpose of computer simulation are presented in table 4.4 and 4.5.



The results of a picture 4.20 simulation shows the contours of the distribution of stresses von mises produced .Of these pictures , it was that voltage von mises concentrated in the weld area.Can be seen that von mises voltage maximum occurs in weld connection profile .In the area by concentration of the high voltage this is , crack will begin to form and spread to the direction of voltage is smaller .The results of these simulations according to the location of that crack found in a pipe 5 ( see figure 4.21 )