In the process of using tubular heat exchanger, the tube is the part prone to failure. The flushing and corrosion of the medium on the pipe may cause the damage of the pipe, so the heat exchanger is often checked in order to find the fault in time and take corresponding measures for repair.

The common faults of tubular heat exchanger include pipe wall fouling, pipe leakage and vibration.

1. Removal of pipe wall fouling

On the inner and outer wall of tube heat exchanger, it is easy to form a layer of scale due to the frequent existence of medium. The formation of fouling will directly reduce the efficiency of heat exchanger, so it should be removed in time. Mechanical and chemical methods can be used to remove the scale on the inner wall of pipes.

2. Repair of leakage

The tube bundle of tubular heat exchanger is composed of many tubes. The main reason of tube leakage is the erosion and corrosion of medium. Before repairing the pipe, check the leakage of the pipe.

The common methods for checking pipe leakage are as follows:

The low-pressure outlet end of the cooling water is provided with a sampling pipe orifice, and the cooling water is sampled and analyzed regularly. If the cooling water contains the component of the medium to be cooled, there is leakage in the tube bundle. Then the pressure test method is used to check which pipes in the tube bundle are leaking.

During the inspection, a blind plate is added at one end of the tube bundle, and the tube bundle is immersed in the pool, and then the pressure is not greater than 1 × 100000 PA of compressed air, respectively, into each nozzle for testing.

When compressed air passes into a pipe orifice, if there are bubbles in the pool, it means that the officer has leakage, then mark the pipe orifice. This method is used to inspect all the pipes, and different repair methods are used according to the number of damaged pipes.

Repair method of pipe leakage

1. Repair method for small amount of pipe leakage

If only one or several tubes in the tube bundle leak, considering that it has little effect on the heat exchange efficiency of the heat exchanger, the method of plugging can be used to repair the leaking tubes. Fasten and weld the two ends of the pipe with conical metal plug to block the damaged pipe.

The taper of the conical metal plug should be 3-5 ℃, and the diameter of the big end of the plug should be slightly larger than the inner diameter of the expanded pipe.

2. Repair method for more pipe leakage

If there are many leaking pipes, the heat exchange efficiency of the heat exchanger will be greatly reduced by using the plugging method (generally, the number of blocked pipes cannot exceed 10% of the number of main pipes).

At this time, the method of replacing the pipe is adopted for repair, and the operation steps are as follows:;

(1) Remove the leaking pipe

The removal of the tube is the process of pulling the tube out of the tubesheet. When removing the pipe, the thin-walled non-ferrous metal pipe can be removed by drilling or reaming, or by chiseling the pipe orifice with a sharp chisel.

When the pipe is removed by drilling or reaming, the diameter of the drill or reamer shall be equal to the inner diameter of the orifice on the tubesheet.

When drilling or reaming, the basic metal of the expanding part of the pipe in the orifice of the tube sheet is cut off, and the pipe can be removed from the tube sheet. When the pipe is removed by chiseling, a sharp chisel can be used to shrink the orifice of the expanding part inward, so as to separate the pipe from the tube sheet and remove the pipe from the orifice of the tube sheet.

For the pipe with large wall thickness, the oxygen acetylene flame cutting method can be used to remove the pipe, that is, first cut 2-4 notches in the expansion part of the pipe, and knock the nozzle inward to shrink, so that the pipe is separated from the orifice on the tube sheet, and then use the screw Jack to push the pipe out or pull out with the pulling tool.

No matter which method is used to remove the pipe, both ends of the pipe should be removed, and attention should be paid to not damage the orifice of the tubesheet during the removal, so that the pipe and the tubesheet can be tightly connected when the new pipe is replaced.

(2) Replace the new pipe and expand it

After the damaged pipe is pulled out from the tube sheet, the new pipe can be inserted into the hole of the tube sheet. Replace the new pipe with the same specification and material as the original pipe.

When threading the pipe, the corresponding orifice of the tube sheet should be aligned to make the pipe in the correct position. Then you can connect the tube to the tubesheet.