1. Reasons for Leakage of Heat Exchanger Tube Orifices

1.1 Excessive thermal stress

During operation, the temperature of the shell and tube walls of a tubular heat exchanger varies between cold and hot fluids due to temperature differences. This difference results in different thermal expansion between the shell and the tube. When the temperature difference between the two is large, the pipe may be twisted, or the pipe may stretch from the flower board, and may even damage the entire heat exchanger. In this regard, it is necessary to consider the impact of thermal expansion on the structure and adopt various compensation methods.

When the heat exchanger starts and stops, the heating and cooling rates exceed the regulations, causing significant thermal stress on the tubes and plates, and damage to the welds or expansion joints connecting the tubes. Causing port leakage.

1.2 Tube plate deformation

The main deformation is the processing deformation of the tube plate and the deformation generated during the processing. The tube is connected to the tube plate, and deformation of the tube plate can cause air leakage at the tube mouth.

1.3 Improper plugging process

Generally, cone plug welding is used to plug the pipe. Use moderate force when driving the conical plug; Excessive hammering force can cause deformation of the pipe hole, affecting the connection between adjacent pipes and the pipe plate, causing damage and new leaks.

During the welding process, if the preheating, weld position, and size are not appropriate, it can cause damage to the connection between adjacent pipes and tube plates. Using other plugging methods, such as expanding and exploding, can also cause adjacent pipe openings to leak if the process is improper. Therefore, strict pipeline blockage techniques should be followed.

2. Reasons for leakage of titanium heat exchange tubes themselves

2.1 Scouring

One of the reasons is that when the steam flow rate is high and the steam flow rate contains large water droplets, the outer wall of the pipeline is thinned by the two-phase flow of steam and water, causing perforation or bulging under the supply pressure. Another reason is the direct impact of steam or hydrophobicity. Because the material and fixing method of the anti cleaning board are unreasonable. Fracture or detachment during operation, loss of anti erosion protection; The area of the anti erosion plate is not large enough, and water droplets move with high-speed airflow and collide with the pipe bundle outside the anti erosion plate; The distance between the shell and the tube bundle is too small, resulting in high steam flow velocity at the inlet.

2.2 Tube vibration

When the feed water temperature is too low or the unit is overloaded, and the steam flow rate and speed between the heat exchanger tubes exceed the design value, the tube bundle has a certain elasticity. Vibration occurs under the action of fluid disturbance on the shell side. When the frequency of the excitation force matches the natural vibration frequency or its multiple of the tube bundle, it will cause resonance of the tube bundle, greatly increasing the amplitude, and thus connecting the tube to the tube plate. The bundle is repeatedly damaged by force.

Corrosion at the inlet end of pipeline water supply

2.3 Corrosion damage at the inlet end of the pipeline only occurs in carbon steel heat exchangers. It is a destructive process that combines erosion and corrosion: its mechanism is that the oxide film formed on the metal surface of the pipe wall is destroyed and carried away by high turbulence water supply, and the metal material continuously loses. Ultimately leading to pipeline damage.

2.4 Corrosion

When the pipe material of the low-pressure titanium heat exchanger is copper, the copper pipe is often forced to be replaced due to severe leakage. When the pH value is between 8.5 and 8.8, the corrosion rate of copper is the lowest. Carbon steel requires a pH value of no less than 9.5.

2.5 Poor materials and craftsmanship

The material of the pipe is poor, the thickness of the pipe wall is uneven, there are defects before the assembly of the pipe, the bulge is too large, and there are signs of damage on the outer side of the tensile pipe. When the heat exchanger encounters abnormal situations, it can cause significant damage to the pipes.