Seeking help with reboiler leakage issue
Thread Content
Steam reboiler: the shell-side fluid is steam at 0.5 Mpa and a temperature of 150 degrees Celsius; the tube side contains a non-corrosive fluid at around 0.1 Mpa and a temperature of about 105 degrees Celsius. The heat exchange tubes are made of 10# steel, while the tube sheet is made of Q345R. The heater has a fixed tube sheet design and is installed vertically. During normal operation, leaks frequently occur in the welds between the heat exchange tubes and the tube sheet at the upper part of the heater, while leaks in the lower welds are rare. The majority of leaks occur in the upper section. The equipment is used for approximately 3 months before problems arise. I would appreciate it if experts could explain what might be causing this issue
The structural design and installation method are unreasonable
There are no corrosive agents; the weld fatigue cracking must be caused by steam impact. For heat exchanger tubes, it is recommended to use strength expansion combined with strength welding; in addition, reinforcement measures should be taken for these tubes, such as the addition of baffle plates or other reinforcing elements. Anti-overflow baffles and distributors should be installed at the steam inlet to the heat exchanger.
Agree with the statement that 【the structural format and installation method are unreasonable】. Steam definitely flows upward and exits downward, while the fluid in the tube side flows downward and exits upward; as a result, the temperature at the upper part is relatively high, generating greater tensile stress that leads to leaks in the welds of the tubes at the upper part.
In a thermal siphon reboiler, the lower section of the tube side is the vaporization zone where heating begins, while the upper section is the evaporation zone. The vaporization and evaporation process is accompanied by factors such as water hammer, vibration, and thermal shock, which leads to fatigue cracking in the welds between the upper heat exchange tubes and the tube sheet. The fixed tube sheet structure is not very reasonable.
The flow loss issue causes a temperature difference between the upper and lower parts, leading to stress on the equipment and deformation of the feet, which results in cracks. Water hammer inside the equipment or fluctuations in heating temperature, which cause significant internal shocks, can also lead to similar results. To determine the true cause, it is necessary to understand the details of the scene.